nimdoc: CSS: fix rendering of inline code spans (#25605)

I've been wondering why the inline code was rendered wrapped with no
regards to words/whitespace for a while.

Partially reverts 8b82f5 (#24927)

- `word-break: break-all;` This is seriously wrong, replaced with
`overflow-wrap: break-word;`
- `white-space: normal;` -> `pre-wrap;` to preserve whitespace in code
spans.
- Added `display: block;` and `overflow-x: auto;` to tables. This
contains wide tables with their own scrollbars without stretching the
whole doc.
- `overflow-x: hidden;` just clips content and possibly conflicts with
navbar's `sticky` attribute. Removed.

.github/dependabot.yml

@@ -0,0 +1,11 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "github-actions" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "weekly"

.github/workflows/bisects.yml

@@ -15,7 +15,7 @@ jobs:
     name: ${{ matrix.platform }}-bisects
     runs-on: ${{ matrix.platform }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Install OpenSSL (Windows)
         if: |

.github/workflows/ci_docs.yml

@@ -53,7 +53,7 @@ jobs:
 
     steps:
       - name: 'Checkout'
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 2
 
@@ -109,7 +109,7 @@ jobs:
         if: |
           github.event_name == 'push' && github.ref == 'refs/heads/devel' &&
           matrix.target == 'linux'
-        uses: crazy-max/ghaction-github-pages@v4
+        uses: crazy-max/ghaction-github-pages@v5
         with:
           build_dir: doc/html
         env:

.github/workflows/ci_packages.yml

@@ -33,14 +33,14 @@ jobs:
       NIM_TESTAMENT_BATCH: ${{ matrix.batch }}
     steps:
       - name: 'Checkout'
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 2
 
-      - name: 'Install node.js 20.x'
-        uses: actions/setup-node@v4
+      - name: 'Install node.js'
+        uses: actions/setup-node@v6
         with:
-          node-version: '20.x'
+          node-version: 24
 
       - name: 'Install dependencies (Linux amd64)'
         if: runner.os == 'Linux' && matrix.cpu == 'amd64'

.github/workflows/ci_publish.yml

@@ -17,14 +17,14 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - name: 'Checkout'
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 2
 
       - name: 'Install node.js'
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v6
         with:
-          node-version: ''
+          node-version: 24
 
       - name: 'Install dependencies (Linux amd64)'
         if: runner.os == 'Linux' && matrix.cpu == 'amd64'
@@ -60,7 +60,7 @@ jobs:
         run: nim c -r -d:release ci/action.nim
 
       - name: 'Comment'
-        uses: actions/github-script@v7
+        uses: actions/github-script@v8
         with:
           script: |
             const fs = require('fs');

.github/workflows/stale.yml

@@ -9,7 +9,7 @@ jobs:
   stale:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/stale@v9
+      - uses: actions/stale@v10
         with:
           days-before-pr-stale:    365
           days-before-pr-close:    30

changelog.md

@@ -33,7 +33,7 @@ errors.
 
 - Bitshift operators (`shl`, `shr`, `ashr`) now apply bitmasking to the right operand in the C/C++/VM/JS backends.
 
-- Adds a new warning enabled by `--warning:ImplicitRangeConversion` that detects downsizing implicit conversions to range types (e.g., `int -> range[0..255]` or `range[1..256] -> range[0..255]`) that could cause runtime panics. Safe conversions like `range[0..255] -> range[0..65535]` and explicit casts are not warned on.
+- Adds a new warning `--warning:ImplicitRangeConversion` that detects downsizing implicit conversions to range types (e.g., `int -> range[0..255]` or `range[1..256] -> range[0..255]`) that could cause runtime panics. Safe conversions like `range[0..255] -> range[0..65535]` and explicit casts do not trigger warnings. `int` to `Natural` and `Positive` conversions do not trigger warnings, which can be enabled with `--warning:systemRangeConversion`.
 
 ## Standard library additions and changes
 
@@ -61,6 +61,10 @@ errors.
 
 - `system.setLenUninit` now supports refc, JS and VM backends.
 
+- `std/parseopt` now supports multiple parser modes via a `CliMode` enum.
+  Modes include `Nim` (default, fully compatible) and two new experimental modes:
+  `Lax` and `Gnu` for different option parsing behaviors.
+
 [//]: # "Changes:"
 
 - `std/math` The `^` symbol now supports floating-point as exponent in addition to the Natural type.

compiler/ast.nim

@@ -1270,7 +1270,8 @@ template transitionSymKindCommon*(k: TSymKind) =
   s[] = TSym(kindImpl: k, itemId: obj.itemId, magicImpl: obj.magicImpl, typImpl: obj.typImpl, name: obj.name,
              infoImpl: obj.infoImpl, ownerFieldImpl: obj.ownerFieldImpl, flagsImpl: obj.flagsImpl, astImpl: obj.astImpl,
              optionsImpl: obj.optionsImpl, positionImpl: obj.positionImpl, offsetImpl: obj.offsetImpl,
-             locImpl: obj.locImpl, annexImpl: obj.annexImpl, constraintImpl: obj.constraintImpl)
+             disamb: obj.disamb, locImpl: obj.locImpl, annexImpl: obj.annexImpl, constraintImpl: obj.constraintImpl,
+             instantiatedFromImpl: obj.instantiatedFromImpl)
   when hasFFI:
     s.cnameImpl = obj.cnameImpl
   when defined(nimsuggest):

compiler/ast2nif.nim

@@ -910,20 +910,20 @@ proc loadSymFromCursor(c: var DecodeContext; s: PSym; n: var Cursor; thisModule:
 proc createTypeStub(c: var DecodeContext; t: SymId): PType =
   let name = pool.syms[t]
   assert name.startsWith("`t")
-  var i = len("`t")
-  var k = 0
-  while i < name.len and name[i] in {'0'..'9'}:
-    k = k * 10 + name[i].ord - ord('0')
-    inc i
-  if i < name.len and name[i] == '.': inc i
-  var itemId = 0'i32
-  while i < name.len and name[i] in {'0'..'9'}:
-    itemId = itemId * 10'i32 + int32(name[i].ord - ord('0'))
-    inc i
-  if i < name.len and name[i] == '.': inc i
-  let suffix = name.substr(i)
   result = c.types.getOrDefault(name)[0]
   if result == nil:
+    var i = len("`t")
+    var k = 0
+    while i < name.len and name[i] in {'0'..'9'}:
+      k = k * 10 + name[i].ord - ord('0')
+      inc i
+    if i < name.len and name[i] == '.': inc i
+    var itemId = 0'i32
+    while i < name.len and name[i] in {'0'..'9'}:
+      itemId = itemId * 10'i32 + int32(name[i].ord - ord('0'))
+      inc i
+    if i < name.len and name[i] == '.': inc i
+    let suffix = name.substr(i)
     let id = ItemId(module: moduleId(c, suffix).int32, item: itemId)
     let offs = c.getOffset(id.module.FileIndex, name)
     result = PType(itemId: id, uniqueId: id, kind: TTypeKind(k), state: Partial)
@@ -944,30 +944,26 @@ proc extractLocalSymsFromTree(c: var DecodeContext; n: var Cursor; thisModule: s
       if n.tagId == sdefTag:
         # Found an sdef - check if it's local
         let name = n.firstSon
-        if name.kind == SymbolDef:
-          let symName = pool.syms[name.symId]
-          let sn = parseSymName(symName)
-          if sn.module.len == 0 and symName notin localSyms:
-            # Local symbol - create stub and immediately load it fully
-            # since local symbols have no index offsets for lazy loading
-            let module = moduleId(c, thisModule)
-            let val = addr c.mods[module].symCounter
-            inc val[]
-            let id = ItemId(module: module.int32, item: val[])
-            let sym = PSym(itemId: id, kindImpl: skStub, name: c.cache.getIdent(sn.name),
-                          disamb: sn.count.int32, state: Complete)
-            localSyms[symName] = sym
-            # Load the full symbol definition immediately
-            # We're currently at the `(sd` position, need to skip to SymbolDef
-            inc n  # skip past `sd` tag to get to SymbolDef
-            inc depth  # account for the opening `(` of the sdef
-            loadSymFromCursor(c, sym, n, thisModule, localSyms)
-            sym.state = Sealed  # mark as fully loaded
-            # loadSymFromCursor consumed everything including the closing `)`,
-            # so we need to account for it in depth tracking
-            dec depth
-            # Continue processing - loadSymFromCursor already advanced n past the closing `)`
-            continue
+        expect name, SymbolDef
+        let symName = pool.syms[name.symId]
+        let sn = parseSymName(symName)
+        if sn.module.len == 0 and symName notin localSyms:
+          # Local symbol - create stub and immediately load it fully
+          # since local symbols have no index offsets for lazy loading
+          let module = moduleId(c, thisModule)
+          let val = addr c.mods[module].symCounter
+          inc val[]
+          let id = ItemId(module: module.int32, item: val[])
+          let sym = PSym(itemId: id, kindImpl: skStub, name: c.cache.getIdent(sn.name),
+                        disamb: sn.count.int32, state: Complete)
+          localSyms[symName] = sym
+          # Load the full symbol definition immediately
+          # We're currently at the `(sd` position, need to skip to SymbolDef
+          inc n  # skip past `sd` tag to get to SymbolDef
+          loadSymFromCursor(c, sym, n, thisModule, localSyms)
+          sym.state = Sealed  # mark as fully loaded
+          # Continue processing - loadSymFromCursor already advanced n past the closing `)`
+          continue
       inc depth
     elif n.kind == ParRi:
       dec depth

compiler/astdef.nim

@@ -202,7 +202,11 @@ type
     tySequence,
     tyProc,
     tyPointer, tyOpenArray,
-    tyString, tyCstring, tyForward,
+    tyString, tyCstring,
+    tyForward,
+      # a type not yet semchecked
+      # When semcheck a type section, all types defined in it are initialized to tyForward
+
     tyInt, tyInt8, tyInt16, tyInt32, tyInt64, # signed integers
     tyFloat, tyFloat32, tyFloat64, tyFloat128,
     tyUInt, tyUInt8, tyUInt16, tyUInt32, tyUInt64,
@@ -697,6 +701,7 @@ type
 
   PLib* = ref TLib
   TSym* {.acyclic.} = object # Keep in sync with ast2nif.nim
+                             # Check `transitionSymKindCommon` in ast.nim when add a new field.
     itemId*: ItemId
     # proc and type instantiations are cached in the generic symbol
     state*: ItemState

compiler/ccgexprs.nim

@@ -216,6 +216,8 @@ proc genOptAsgnTuple(p: BProc, dest, src: TLoc, flags: TAssignmentFlags) =
       flags
   let t = skipTypes(dest.t, abstractInst).getUniqueType()
   for i, t in t.ikids:
+    # Do not produce code for void types
+    if isEmptyType(t): continue
     let field = "Field$1" % [i.rope]
     genAssignment(p, optAsgnLoc(dest, t, field),
                      optAsgnLoc(src, t, field), newflags)
@@ -920,8 +922,8 @@ proc genDeref(p: BProc, e: PNode, d: var TLoc) =
     else:
       a = initLocExprSingleUse(p, e[0])
 
-    if e.typ != nil and e.typ.kind == tyObject:
-      # bug #23453 #25265
+    # bug #23453 #25265
+    if e.typ != nil and e.typ.skipTypes(abstractInst).kind == tyObject:
       discard getTypeDesc(p.module, e.typ)
     if d.k == locNone:
       # dest = *a;  <-- We do not know that 'dest' is on the heap!
@@ -1587,6 +1589,51 @@ proc genSeqElemAppend(p: BProc, e: PNode, d: var TLoc) =
   genAssignment(p, dest, b, {needToCopy})
   gcUsage(p.config, e)
 
+proc genSeqElemAppendV2(p: BProc, e: PNode, d: var TLoc) =
+  # s.add(x) with optSeqDestructors (arc/orc), inlined for direct slot construction:
+  #   NI oldLen = s.len;
+  #   if (s.p == NIM_NIL || (s.p->cap & ~NIM_STRLIT_FLAG) < oldLen + 1)
+  #     s.p = (PayloadType*)prepareSeqAddUninit(oldLen, s.p, 1, sizeof(T), alignof(T));
+  #   s.len = oldLen + 1;
+  #   s.p->data[oldLen] = x;  // direct assignment, no function call overhead
+  let seqtype = skipTypes(e[1].typ, abstractVarRange)
+  var a = initLocExpr(p, e[1])
+  let pt = getSeqPayloadType(p.module, seqtype)
+  let pe = seqPayloadElem(p.module, seqtype)
+  # Capture a stable pointer to the seq BEFORE evaluating the element (e[2]).
+  # Evaluating e[2] may emit move semantics (eqwasMoved) that nil a variable
+  # through which e[1]'s snippet is accessed (e.g. a closure env pointer).
+  inc(p.labels)
+  let seqPtrName = "T" & rope(p.labels) & "_"
+  p.s(cpsLocals).addVar(kind = Local, name = seqPtrName,
+                        typ = ptrType(getTypeDesc(p.module, seqtype)))
+  p.s(cpsStmts).addAssignment(seqPtrName, cAddr(rdLoc(a)))
+  var b = initLocExpr(p, e[2])
+  # All seq operations now go through the stable seqPtrName pointer.
+  let ra = wrapPar(cDeref(seqPtrName))
+  var tmpL = getIntTemp(p)
+  p.s(cpsStmts).addAssignment(tmpL.snippet, dotField(ra, "len"))
+  let pField = dotField(ra, "p")
+  p.s(cpsStmts).addSingleIfStmt(
+      cOp(Or,
+        cOp(Equal, pField, NimNil),
+        cOp(LessThan,
+          cOp(BitAnd, NimInt, derefField(pField, "cap"), cOp(BitNot, NimInt, NimStrlitFlag)),
+          cOp(Add, NimInt, tmpL.snippet, cIntValue(1))))):
+    p.s(cpsStmts).addFieldAssignmentWithValue(ra, "p"):
+      p.s(cpsStmts).addCast(ptrType(pt)):
+        p.s(cpsStmts).addCall(cgsymValue(p.module, "prepareSeqAddUninit"),
+          tmpL.snippet,
+          pField,
+          cIntValue(1),
+          cSizeof(pe),
+          cAlignof(pe))
+  p.s(cpsStmts).addFieldAssignment(ra, "len",
+    cOp(Add, NimInt, tmpL.snippet, cIntValue(1)))
+  var dest = initLoc(locExpr, e[2], OnHeap)
+  dest.snippet = subscript(dataField(p, ra), tmpL.snippet)
+  genAssignment(p, dest, b, {})
+
 proc genDefault(p: BProc; n: PNode; d: var TLoc) =
   if d.k == locNone: d = getTemp(p, n.typ, needsInit=true)
   else: resetLoc(p, d)
@@ -1722,15 +1769,15 @@ proc genNewSeq(p: BProc, e: PNode) =
     let seqtype = skipTypes(e[1].typ, abstractVarRange)
     let ra = a.rdLoc
     let rb = b.rdLoc
-    let et = getTypeDesc(p.module, seqtype.elementType)
     let pt = getSeqPayloadType(p.module, seqtype)
+    let pe = seqPayloadElem(p.module, seqtype)
     p.s(cpsStmts).addFieldAssignment(ra, "len", rb)
     p.s(cpsStmts).addFieldAssignmentWithValue(ra, "p"):
       p.s(cpsStmts).addCast(ptrType(pt)):
         p.s(cpsStmts).addCall(cgsymValue(p.module, "newSeqPayload"),
           rb,
-          cSizeof(et),
-          cAlignof(et))
+          cSizeof(pe),
+          cAlignof(pe))
   else:
     let lenIsZero = e[2].kind == nkIntLit and e[2].intVal == 0
     genNewSeqAux(p, a, b.rdLoc, lenIsZero)
@@ -1743,15 +1790,15 @@ proc genNewSeqOfCap(p: BProc; e: PNode; d: var TLoc) =
     if d.k == locNone: d = getTemp(p, e.typ, needsInit=false)
     let rd = d.rdLoc
     let ra = a.rdLoc
-    let et = getTypeDesc(p.module, seqtype.elementType)
     let pt = getSeqPayloadType(p.module, seqtype)
+    let pe = seqPayloadElem(p.module, seqtype)
     p.s(cpsStmts).addFieldAssignment(rd, "len", cIntValue(0))
     p.s(cpsStmts).addFieldAssignmentWithValue(rd, "p"):
       p.s(cpsStmts).addCast(ptrType(pt)):
         p.s(cpsStmts).addCall(cgsymValue(p.module, "newSeqPayloadUninit"),
           ra,
-          cSizeof(et),
-          cAlignof(et))
+          cSizeof(pe),
+          cAlignof(pe))
   else:
     if d.k == locNone: d = getTemp(p, e.typ, needsInit=false) # bug #22560
     let ra = a.rdLoc
@@ -1887,15 +1934,15 @@ proc genSeqConstr(p: BProc, n: PNode, d: var TLoc) =
   if optSeqDestructors in p.config.globalOptions:
     let seqtype = n.typ
     let rd = rdLoc dest[]
-    let et = getTypeDesc(p.module, seqtype.elementType)
     let pt = getSeqPayloadType(p.module, seqtype)
+    let pe = seqPayloadElem(p.module, seqtype)
     p.s(cpsStmts).addFieldAssignment(rd, "len", lit)
     p.s(cpsStmts).addFieldAssignmentWithValue(rd, "p"):
       p.s(cpsStmts).addCast(ptrType(pt)):
         p.s(cpsStmts).addCall(cgsymValue(p.module, "newSeqPayload"),
           lit,
-          cSizeof(et),
-          cAlignof(et))
+          cSizeof(pe),
+          cAlignof(pe))
   else:
     # generate call to newSeq before adding the elements per hand:
     genNewSeqAux(p, dest[], lit, n.len == 0)
@@ -1928,15 +1975,15 @@ proc genArrToSeq(p: BProc, n: PNode, d: var TLoc) =
     let seqtype = n.typ
     let rd = rdLoc d
     let valL = cIntValue(L)
-    let et = getTypeDesc(p.module, seqtype.elementType)
     let pt = getSeqPayloadType(p.module, seqtype)
+    let pe = seqPayloadElem(p.module, seqtype)
     p.s(cpsStmts).addFieldAssignment(rd, "len", valL)
     p.s(cpsStmts).addFieldAssignmentWithValue(rd, "p"):
       p.s(cpsStmts).addCast(ptrType(pt)):
         p.s(cpsStmts).addCall(cgsymValue(p.module, "newSeqPayload"),
           valL,
-          cSizeof(et),
-          cAlignof(et))
+          cSizeof(pe),
+          cAlignof(pe))
   else:
     let lit = cIntLiteral(L)
     genNewSeqAux(p, d, lit, L == 0)
@@ -2898,8 +2945,15 @@ proc genMagicExpr(p: BProc, e: PNode, d: var TLoc, op: TMagic) =
   of mAppendStrStr: genStrAppend(p, e, d)
   of mAppendSeqElem:
     if optSeqDestructors in p.config.globalOptions:
-      e[1] = makeAddr(e[1], p.module.idgen)
-      genCall(p, e, d)
+      if p.config.selectedGC in {gcArc, gcAtomicArc, gcOrc}:
+        # Inline growth + direct slot assignment: avoids the add() call overhead
+        # and lets the C compiler see the construction expression at its final
+        # destination, enabling in-place construction for nkObjConstr etc.
+        # gcYrc is excluded because its add() acquires a striped reader lock.
+        genSeqElemAppendV2(p, e, d)
+      else:
+        e[1] = makeAddr(e[1], p.module.idgen)
+        genCall(p, e, d)
     else:
       genSeqElemAppend(p, e, d)
   of mEqStr: genStrEquals(p, e, d)
@@ -3155,6 +3209,8 @@ proc genTupleConstr(p: BProc, n: PNode, d: var TLoc) =
     for i in 0..<n.len:
       var it = n[i]
       if it.kind == nkExprColonExpr: it = it[1]
+      # Do not produce code for void types
+      if it.typ != nil and isEmptyType(it.typ): continue
       rec = initLoc(locExpr, it, dest[].storage)
       rec.snippet = dotField(rdLoc(dest[]), "Field" & rope(i))
       rec.flags.incl(lfEnforceDeref)
@@ -3271,7 +3327,11 @@ proc upConv(p: BProc, n: PNode, d: var TLoc) =
         p.s(cpsStmts).addCallStmt(cgsymValue(p.module, "raiseObjectConversionError"))
         raiseInstr(p, p.s(cpsStmts))
 
-  if n[0].typ.kind != tyObject:
+  # skip cast when types map to the same C type
+  # this avoids invalid C code like `*(T*)&x` for types that can't have their address taken (e.g., WASM __externref_t)
+  if getTypeDesc(p.module, n.typ) == getTypeDesc(p.module, n[0].typ):
+    expr(p, n[0], d)
+  elif n[0].typ.kind != tyObject:
     let destTyp = getTypeDesc(p.module, n.typ)
     let val = rdLoc(a)
     if n.isLValue:
@@ -3317,7 +3377,7 @@ proc downConv(p: BProc, n: PNode, d: var TLoc) =
         cCast(ptrType(destType),
           wrapPar(cAddr(wrapPar(val))))),
       a.storage)
-  elif p.module.compileToCpp:
+  elif p.module.compileToCpp or isImportedType(src):
     # C++ implicitly downcasts for us
     expr(p, arg, d)
   else:
@@ -3762,6 +3822,7 @@ proc containsOpaqueImportcField(typ: PType): bool =
       return true
   of tyTuple:
     for i, a in t.ikids:
+      if isEmptyType(a): continue
       if containsOpaqueImportcField(a):
         return true
   of tyArray:
@@ -3811,10 +3872,12 @@ proc getDefaultValue(p: BProc; typ: PType; info: TLineInfo; result: var Builder)
     var tupleInit: StructInitializer
     let initKind = if containsOpaqueImportcField(t): siNamedStruct else: siOrderedStruct
     result.addStructInitializer(tupleInit, kind = initKind):
-      if p.vccAndC and t.isEmptyTupleType:
+      if p.vccAndC and validTupleTypeFields(t) == 0:
         result.addField(tupleInit, name = "dummy"):
           result.addIntValue(0)
       for i, a in t.ikids:
+        # Do not produce code for void types
+        if isEmptyType(a): continue
         let elemTyp = skipTypes(a, abstractRange+{tyOwned}-{tyTypeDesc})
         if not isOpaqueImportcType(elemTyp):
           result.addField(tupleInit, name = "Field" & $i):
@@ -3989,6 +4052,8 @@ proc genConstTuple(p: BProc, n: PNode; isConst: bool; tup: PType; result: var Bu
       var it = n[i]
       if it.kind == nkExprColonExpr:
         it = it[1]
+      # Do not produce code for void types
+      if isEmptyType(tup[i]): continue
       result.addField(tupleInit, name = "Field" & $i):
         genBracedInit(p, it, isConst, tup[i], result)
 

compiler/ccgtypes.nim

@@ -453,6 +453,14 @@ proc getSeqPayloadType(m: BModule; t: PType): Rope =
   result = getTypeDescWeak(m, t, check, dkParam) & "_Content"
   #result = getTypeForward(m, t, hashType(t)) & "_Content"
 
+proc seqPayloadElem(m: BModule; t: PType): Snippet =
+  ## Returns the C type name for a seq's element as stored in the payload,
+  ## suitable for sizeof()/alignof(). Must use dkVar, not the dkParam default,
+  ## because reified openArrays (experimental views) differ: dkParam gives a
+  ## bare pointer (T*) while dkVar gives the two-word struct actually stored.
+  var check = initIntSet()
+  result = getTypeDescAux(m, t.elementType, check, dkVar)
+
 proc seqV2ContentType(m: BModule; t: PType; check: var IntSet) =
   let sig = hashType(t, m.config)
   let result = cacheGetType(m.typeCache, sig)
@@ -800,6 +808,8 @@ proc getTupleDesc(m: BModule; typ: PType, name: Rope,
   var res = newBuilder("")
   res.addStruct(m, typ, name, ""):
     for i, a in typ.ikids:
+      # Do not produce code for void types
+      if isEmptyType(a): continue
       res.addField(
         name = "Field" & $i,
         typ = getTypeDescAux(m, a, check, dkField))
@@ -1472,27 +1482,38 @@ proc genObjectInfo(m: BModule; typ, origType: PType, name: Rope; info: TLineInfo
     t.incl tfObjHasKids
     t = t.baseClass
 
+proc validTupleTypeFields(t: PType): int =
+  # we want to treat tuples with only void fields as empty, so we need to exclude void types here:
+  result = 0
+  for a in t.kids:
+    if not isEmptyType(a): inc result
+
 proc genTupleInfo(m: BModule; typ, origType: PType, name: Rope; info: TLineInfo) =
   genTypeInfoAuxBase(m, typ, typ, name, cIntValue(0), info)
   var expr = getNimNode(m)
-  if not typ.isEmptyTupleType:
-    var tmp = getTempName(m) & "_" & $typ.kidsLen
-    genTNimNodeArray(m, tmp, typ.kidsLen)
+  let nonVoidKids = validTupleTypeFields(typ)
+  if nonVoidKids > 0:
+    var tmp = getTempName(m) & "_" & $nonVoidKids
+    genTNimNodeArray(m, tmp, nonVoidKids)
+    var j = 0
     for i, a in typ.ikids:
+      # Do not produce code for void types
+      if isEmptyType(a): continue
       var tmp2 = getNimNode(m)
       let fieldTypInfo = genTypeInfoV1(m, a, info)
-      m.s[cfsTypeInit3].addSubscriptAssignment(tmp, cIntValue(i), cAddr(tmp2))
+      m.s[cfsTypeInit3].addSubscriptAssignment(tmp, cIntValue(j), cAddr(tmp2))
       m.s[cfsTypeInit3].addFieldAssignment(tmp2, "kind", 1)
       m.s[cfsTypeInit3].addFieldAssignmentWithValue(tmp2, "offset"):
         m.s[cfsTypeInit3].addOffsetof(getTypeDesc(m, origType, dkVar), "Field" & $i)
       m.s[cfsTypeInit3].addFieldAssignment(tmp2, "typ", fieldTypInfo)
       m.s[cfsTypeInit3].addFieldAssignment(tmp2, "name", "\"Field" & $i & "\"")
-    m.s[cfsTypeInit3].addFieldAssignment(expr, "len", typ.kidsLen)
+      inc j
+    m.s[cfsTypeInit3].addFieldAssignment(expr, "len", nonVoidKids)
     m.s[cfsTypeInit3].addFieldAssignment(expr, "kind", 2)
     m.s[cfsTypeInit3].addFieldAssignment(expr, "sons",
       cAddr(subscript(tmp, cIntValue(0))))
   else:
-    m.s[cfsTypeInit3].addFieldAssignment(expr, "len", typ.kidsLen)
+    m.s[cfsTypeInit3].addFieldAssignment(expr, "len", cIntValue(0))
     m.s[cfsTypeInit3].addFieldAssignment(expr, "kind", 2)
   m.s[cfsTypeInit3].addFieldAssignment(tiNameForHcr(m, name), "node", cAddr(expr))
 

compiler/closureiters.nim

@@ -139,7 +139,7 @@
 
 import
   ast, msgs, idents,
-  renderer, magicsys, lowerings, lambdalifting, modulegraphs, lineinfos
+  renderer, magicsys, lowerings, lambdalifting, modulegraphs, lineinfos, trees
 
 import std/tables
 
@@ -727,7 +727,7 @@ proc lowerStmtListExprs(ctx: var Ctx, n: PNode, needsSplit: var bool): PNode =
       n[0] = ex
       result.add(n)
 
-  of nkCast, nkHiddenStdConv, nkHiddenSubConv, nkConv, nkObjDownConv,
+  of nkCast, nkHiddenStdConv, nkHiddenSubConv, nkConv, nkObjDownConv, nkObjUpConv,
       nkDerefExpr, nkHiddenDeref:
     var ns = false
     for i in ord(n.kind == nkCast)..<n.len:
@@ -1390,18 +1390,34 @@ proc optimizeStates(ctx: var Ctx) =
   for i in 0 .. ctx.states.high:
     ctx.states[i].label.intVal = i
 
+proc detectCapturedSym(c: var Ctx, s: PSym, stateIdx: int) =
+  if s.kind in {skResult, skVar, skLet, skForVar, skTemp} and sfGlobal notin s.flags and s.owner == c.fn and s != c.externExcSym:
+    let vs = c.varStates.getOrDefault(s.itemId, localNotSeen)
+    if vs == localNotSeen: # First seing this variable
+      c.varStates[s.itemId] = stateIdx
+    elif vs == localRequiresLifting:
+      discard # Sym already marked
+    elif vs != stateIdx:
+      c.captureVar(s)
+
+proc isClosureIterLocal(c: Ctx, s: PSym): bool =
+  s.kind in {skResult, skVar, skLet, skForVar, skTemp} and
+  sfGlobal notin s.flags and s.owner == c.fn and s != c.externExcSym
+
 proc detectCapturedVars(c: var Ctx, n: PNode, stateIdx: int) =
   case n.kind
   of nkSym:
     let s = n.sym
-    if s.kind in {skResult, skVar, skLet, skForVar, skTemp} and sfGlobal notin s.flags and s.owner == c.fn and s != c.externExcSym:
-      let vs = c.varStates.getOrDefault(s.itemId, localNotSeen)
-      if vs == localNotSeen: # First seing this variable
-        c.varStates[s.itemId] = stateIdx
-      elif vs == localRequiresLifting:
-        discard # Sym already marked
-      elif vs != stateIdx:
-        c.captureVar(s)
+    detectCapturedSym(c, s, stateIdx)
+  of nkAddr, nkHiddenAddr:
+    let s = getRoot(n)
+    if s != nil and isClosureIterLocal(c, s):
+      detectCapturedSym(c, s, stateIdx)
+      # bug #25596; lifetime extension for `addr`-taken locals as
+      # we claim ARC/ORC do destruction based on scopes, not on last-usages.
+      c.captureVar(s)
+    for i in 0 ..< n.safeLen:
+      detectCapturedVars(c, n[i], stateIdx)
   of nkReturnStmt:
     if n[0].kind in {nkAsgn, nkFastAsgn, nkSinkAsgn}:
       # we have a `result = result` expression produced by the closure

compiler/docgen.nim

@@ -540,10 +540,11 @@ proc nodeToHighlightedHtml(d: PDoc; n: PNode; result: var string;
       elif s != nil and s.kind in {skType, skVar, skLet, skConst} and
            sfExported in s.flags and s.owner != nil and
            belongsToProjectPackage(d.conf, s.owner) and d.target == outHtml:
-        let external = externalDep(d, s.owner)
-        result.addf "<a href=\"$1#$2\"><span class=\"Identifier\">$3</span></a>",
-          [changeFileExt(external, "html"), literal,
-           escLit]
+        let href = (if d.module == s.owner: ""
+            else: externalDep(d, s.owner).changeFileExt("html")
+          ) & "#" & literal
+        result.addf "<a href=\"$1\"><span class=\"Identifier\">$2</span></a>",
+            [href, escLit]
       else:
         dispA(d.conf, result, "<span class=\"Identifier\">$1</span>",
               "\\spanIdentifier{$1}", [escLit])

compiler/injectdestructors.nim

@@ -72,9 +72,11 @@ proc hasDestructor(c: Con; t: PType): bool {.inline.} =
     if not result and c.graph.config.selectedGC in {gcArc, gcOrc, gcYrc, gcAtomicArc}:
       assert(not containsGarbageCollectedRef(t))
 
-proc getTemp(c: var Con; s: var Scope; typ: PType; info: TLineInfo): PNode =
+proc getTemp(c: var Con; s: var Scope; typ: PType; info: TLineInfo; needsInit: bool): PNode =
   let sym = newSym(skTemp, getIdent(c.graph.cache, ":tmpD"), c.idgen, c.owner, info)
   sym.typ = typ
+  if not needsInit:
+    sym.incl sfNoInit
   s.vars.add(sym)
   result = newSymNode(sym)
 
@@ -302,7 +304,7 @@ proc genSink(c: var Con; s: var Scope; dest, ri: PNode; flags: set[MoveOrCopyFla
       if deepAliases(dest, ri):
         # consider: x = x + y, it is wrong to destroy the destination first!
         # tmp to support self assignments
-        let tmp = c.getTemp(s, dest.typ, dest.info)
+        let tmp = c.getTemp(s, dest.typ, dest.info, needsInit = false)
         result = newTree(nkStmtList, newTree(nkFastAsgn, tmp, dest), newTree(nkFastAsgn, dest, ri),
                          c.genDestroy(tmp))
       else:
@@ -371,7 +373,7 @@ proc genDiscriminantAsgn(c: var Con; s: var Scope; n: PNode): PNode =
   # but fields within active case branch might need destruction
 
   # tmp to support self assignments
-  let tmp = c.getTemp(s, n[1].typ, n.info)
+  let tmp = c.getTemp(s, n[1].typ, n.info, needsInit = false)
 
   result = newTree(nkStmtList)
   result.add newTree(nkFastAsgn, tmp, p(n[1], c, s, consumed))
@@ -457,49 +459,50 @@ proc isCapturedVar(n: PNode): bool =
   else: result = false
 
 proc passCopyToSink(n: PNode; c: var Con; s: var Scope): PNode =
-  result = newNodeIT(nkStmtListExpr, n.info, n.typ)
   let nTyp = n.typ.skipTypes(tyUserTypeClasses)
-  let tmp = c.getTemp(s, nTyp, n.info)
-  if hasDestructorOrAsgn(c, nTyp):
-    let typ = nTyp.skipTypes({tyGenericInst, tyAlias, tySink})
-    let op = getAttachedOp(c.graph, typ, attachedDup)
-    if op != nil and tfHasOwned notin typ.flags:
-      if sfError in op.flags:
-        c.checkForErrorPragma(nTyp, n, "=dup")
-      else:
-        let copyOp = getAttachedOp(c.graph, typ, attachedAsgn)
-        if copyOp != nil and sfError in copyOp.flags and
-           sfOverridden notin op.flags:
-          c.checkForErrorPragma(nTyp, n, "=dup", inferredFromCopy = true)
-
-      let src = p(n, c, s, normal)
-      var newCall = newTreeIT(nkCall, src.info, src.typ,
-            newSymNode(op),
-            src)
-      c.finishCopy(newCall, n, {}, isFromSink = true)
-      result.add newTreeI(nkFastAsgn,
-          src.info, tmp,
-          newCall
-      )
-    else:
-      result.add c.genWasMoved(tmp)
-      var m = c.genCopy(tmp, n, {})
-      m.add p(n, c, s, normal)
-      c.finishCopy(m, n, {}, isFromSink = true)
-      result.add m
-    if isLValue(n) and not isCapturedVar(n) and nTyp.skipTypes(abstractInst).kind != tyRef and c.inSpawn == 0:
-      message(c.graph.config, n.info, hintPerformance,
-        ("passing '$1' to a sink parameter introduces an implicit copy; " &
-        "if possible, rearrange your program's control flow to prevent it") % $n)
-    if c.inEnsureMove > 0:
-      localError(c.graph.config, n.info, errFailedMove,
-        ("cannot move '$1', passing '$1' to a sink parameter introduces an implicit copy") % $n)
-  else:
+  if not hasDestructorOrAsgn(c, nTyp):
+    # Non-managed (plain-old-data) type: no ownership transfer is needed.
+    # Return the expression directly — no temp required.
     if c.graph.config.selectedGC in {gcArc, gcOrc, gcYrc, gcAtomicArc}:
       assert(not containsManagedMemory(nTyp))
     if nTyp.skipTypes(abstractInst).kind in {tyOpenArray, tyVarargs}:
       localError(c.graph.config, n.info, "cannot create an implicit openArray copy to be passed to a sink parameter")
-    result.add newTree(nkAsgn, tmp, p(n, c, s, normal))
+    return p(n, c, s, normal)
+  result = newNodeIT(nkStmtListExpr, n.info, n.typ)
+  let tmp = c.getTemp(s, nTyp, n.info, needsInit = false)
+  let typ = nTyp.skipTypes({tyGenericInst, tyAlias, tySink})
+  let op = getAttachedOp(c.graph, typ, attachedDup)
+  if op != nil and tfHasOwned notin typ.flags:
+    if sfError in op.flags:
+      c.checkForErrorPragma(nTyp, n, "=dup")
+    else:
+      let copyOp = getAttachedOp(c.graph, typ, attachedAsgn)
+      if copyOp != nil and sfError in copyOp.flags and
+         sfOverridden notin op.flags:
+        c.checkForErrorPragma(nTyp, n, "=dup", inferredFromCopy = true)
+
+    let src = p(n, c, s, normal)
+    var newCall = newTreeIT(nkCall, src.info, src.typ,
+          newSymNode(op),
+          src)
+    c.finishCopy(newCall, n, {}, isFromSink = true)
+    result.add newTreeI(nkFastAsgn,
+        src.info, tmp,
+        newCall
+    )
+  else:
+    result.add c.genWasMoved(tmp)
+    var m = c.genCopy(tmp, n, {})
+    m.add p(n, c, s, normal)
+    c.finishCopy(m, n, {}, isFromSink = true)
+    result.add m
+  if isLValue(n) and not isCapturedVar(n) and nTyp.skipTypes(abstractInst).kind != tyRef and c.inSpawn == 0:
+    message(c.graph.config, n.info, hintPerformance,
+      ("passing '$1' to a sink parameter introduces an implicit copy; " &
+      "if possible, rearrange your program's control flow to prevent it") % $n)
+  if c.inEnsureMove > 0:
+    localError(c.graph.config, n.info, errFailedMove,
+      ("cannot move '$1', passing '$1' to a sink parameter introduces an implicit copy") % $n)
   # Since we know somebody will take over the produced copy, there is
   # no need to destroy it.
   result.add tmp
@@ -530,7 +533,7 @@ proc ensureDestruction(arg, orig: PNode; c: var Con; s: var Scope): PNode =
     # produce temp creation for (fn, env). But we need to move 'env'?
     # This was already done in the sink parameter handling logic.
     result = newNodeIT(nkStmtListExpr, arg.info, arg.typ)
-    let tmp = c.getTemp(s, arg.typ, arg.info)
+    let tmp = c.getTemp(s, arg.typ, arg.info, true)
     result.add c.genSink(s, tmp, arg, {IsDecl})
     result.add tmp
     s.final.add c.genDestroy(tmp)
@@ -609,7 +612,7 @@ template processScopeExpr(c: var Con; s: var Scope; ret: PNode, processCall: unt
   # There is a possibility to do this check: s.wasMoved.len > 0 or s.final.len > 0
   # later and use it to eliminate the temporary when theres no need for it, but its
   # tricky because you would have to intercept moveOrCopy at a certain point
-  let tmp = c.getTemp(s.parent[], ret.typ, ret.info)
+  let tmp = c.getTemp(s.parent[], ret.typ, ret.info, needsInit = true)
   tmp.sym.flags = tmpFlags
   let cpy = if hasDestructor(c, ret.typ) and
                 ret.typ.kind notin {tyOpenArray, tyVarargs}:
@@ -770,7 +773,7 @@ proc pRaiseStmt(n: PNode, c: var Con; s: var Scope): PNode =
       result = copyNode(n)
       result.add call
     else:
-      let tmp = c.getTemp(s, n[0].typ, n.info)
+      let tmp = c.getTemp(s, n[0].typ, n.info, needsInit = true)
       var m = c.genCopyNoCheck(tmp, n[0], attachedAsgn)
       m.add p(n[0], c, s, normal)
       c.finishCopy(m, n[0], {}, isFromSink = false)
@@ -1001,6 +1004,13 @@ proc p(n: PNode; c: var Con; s: var Scope; mode: ProcessMode; tmpFlags = {sfSing
         result = moveOrCopy(p(n[0], c, s, mode), n[1], c, s, flags)
       elif isDiscriminantField(n[0]):
         result = c.genDiscriminantAsgn(s, n)
+      elif n[1].kind in {nkStmtListExpr, nkBlockExpr, nkIfExpr, nkCaseStmt, nkTryStmt, nkPragmaBlock}:
+        # Distribute the assignment into each branch to avoid
+        # creating pointless temporaries for expression-based control flow.
+        let dest = p(n[0], c, s, mode)
+        template process(child, s): untyped =
+          newTree(n.kind, dest, p(child, c, s, consumed))
+        handleNestedTempl(n[1], process, willProduceStmt = true)
       else:
         result = copyNode(n)
         result.add p(n[0], c, s, mode)
@@ -1154,7 +1164,7 @@ proc ownsData(c: var Con; s: var Scope; orig: PNode; flags: set[MoveOrCopyFlag])
       break
   if n.kind in nkCallKinds and n.typ != nil and hasDestructor(c, n.typ):
     result = newNodeIT(nkStmtListExpr, orig.info, orig.typ)
-    let tmp = c.getTemp(s, n.typ, n.info)
+    let tmp = c.getTemp(s, n.typ, n.info, needsInit = true)
     tmp.sym.flagsImpl.incl sfSingleUsedTemp
     result.add newTree(nkFastAsgn, tmp, copyTree(n))
     s.final.add c.genDestroy(tmp)

compiler/jsgen.nim

@@ -2018,8 +2018,12 @@ proc createVar(p: PProc, typ: PType, indirect: bool): Rope =
     if indirect: result = "[$1]" % [result]
   of tyTuple:
     result = rope("{")
+    var first = true
     for i in 0..<t.len:
-      if i > 0: result.add(", ")
+      # Do not produce code for void types
+      if isEmptyType(t[i]): continue
+      if not first: result.add(", ")
+      first = false
       result.addf("Field$1: $2", [i.rope,
             createVar(p, t[i], false)])
     result.add("}")

compiler/liftdestructors.nim

@@ -1286,7 +1286,15 @@ proc produceSym(g: ModuleGraph; c: PContext; typ: PType; kind: TTypeAttachedOp;
       tk = tyNone # no special casing for strings and seqs
     case tk
     of tySequence:
+      let needsYrcLock = g.config.selectedGC == gcYrc and
+         kind in {attachedDestructor, attachedSink, attachedAsgn, attachedDeepCopy, attachedDup} and
+         types.canFormAcycle(g, skipped.elementType)
+      # YRC: topology-changing seq ops must hold the mutator (read) lock
+      if needsYrcLock:
+        result.ast[bodyPos].add callCodegenProc(g, "acquireMutatorLock", info)
       fillSeqOp(a, typ, result.ast[bodyPos], d, src)
+      if needsYrcLock:
+        result.ast[bodyPos].add callCodegenProc(g, "releaseMutatorLock", info)
     of tyString:
       fillStrOp(a, typ, result.ast[bodyPos], d, src)
     else:

compiler/lineinfos.nim

@@ -99,6 +99,7 @@ type
     warnUser = "User",
     warnGlobalVarConstructorTemporary = "GlobalVarConstructorTemporary",
     warnImplicitRangeConversion = "ImplicitRangeConversion",
+    warnSystemRangeConversion = "SystemRangeConversion",
     # hints
     hintSuccess = "Success", hintSuccessX = "SuccessX",
     hintCC = "CC",
@@ -208,6 +209,7 @@ const
     warnUser: "$1",
     warnGlobalVarConstructorTemporary: "global variable '$1' initialization requires a temporary variable",
     warnImplicitRangeConversion: "implicit range conversion $1",
+    warnSystemRangeConversion: "implicit range conversion $1",
     hintSuccess: "operation successful: $#",
     # keep in sync with `testament.isSuccess`
     hintSuccessX: "$build\n$loc lines; ${sec}s; $mem; proj: $project; out: $output",
@@ -262,7 +264,7 @@ type
 
 proc computeNotesVerbosity(): array[0..3, TNoteKinds] =
   result = default(array[0..3, TNoteKinds])
-  result[3] = {low(TNoteKind)..high(TNoteKind)} - {warnObservableStores, warnResultUsed, warnAnyEnumConv, warnBareExcept, warnStdPrefix, warnImplicitRangeConversion}
+  result[3] = {low(TNoteKind)..high(TNoteKind)} - {warnObservableStores, warnResultUsed, warnAnyEnumConv, warnBareExcept, warnStdPrefix, warnSystemRangeConversion}
   result[2] = result[3] - {hintStackTrace, hintExtendedContext, hintDeclaredLoc, hintProcessingStmt}
   result[1] = result[2] - {warnProveField, warnProveIndex,
     warnGcUnsafe, hintPath, hintDependency, hintCodeBegin, hintCodeEnd,

compiler/magicsys.nim

@@ -11,7 +11,7 @@
 
 import
   ast, msgs, platform, idents,
-  modulegraphs, lineinfos
+  modulegraphs, lineinfos, types
 
 export createMagic
 
@@ -134,7 +134,7 @@ proc getNimScriptSymbol*(g: ModuleGraph; name: string): PSym =
 proc resetNimScriptSymbols*(g: ModuleGraph) = g.exposed = initStrTable()
 
 proc getMagicEqSymForType*(g: ModuleGraph; t: PType; info: TLineInfo): PSym =
-  case t.kind
+  case t.skipTypes(abstractRange).kind
   of tyInt,  tyInt8, tyInt16, tyInt32, tyInt64,
      tyUInt, tyUInt8, tyUInt16, tyUInt32, tyUInt64:
     result = getSysMagic(g, info, "==", mEqI)

compiler/nim.cfg

@@ -65,3 +65,7 @@ define:useStdoutAsStdmsg
 @if nimHasVtables:
   experimental:vtables
 @end
+
+@if nimHasImplicitRangeConversion:
+  warning[ImplicitRangeConversion]:off
+@end

compiler/semcall.nim

@@ -981,7 +981,7 @@ proc setGenericParams(c: PContext, n, expectedParams: PNode) =
     if e.typ == nil:
       n[i].typ = errorType(c)
     else:
-      n[i].typ = e.typ.skipTypes({tyTypeDesc})
+      n[i].typ = e.typ
 
 proc explicitGenericInstantiation(c: PContext, n: PNode, s: PSym, doError: bool): PNode =
   assert n.kind == nkBracketExpr

compiler/semmagic.nim

@@ -236,6 +236,8 @@ proc evalTypeTrait(c: PContext; traitCall: PNode, operand: PType, context: PSym)
     let complexObj = containsGarbageCollectedRef(t) or
                      hasDestructor(t)
     result = newIntNodeT(toInt128(ord(not complexObj)), traitCall, c.idgen, c.graph)
+  of "canFormCycles":
+    result = newIntNodeT(toInt128(ord(types.canFormAcycle(c.graph, operand))), traitCall, c.idgen, c.graph)
   of "hasDefaultValue":
     result = newIntNodeT(toInt128(ord(not operand.requiresInit)), traitCall, c.idgen, c.graph)
   of "isNamedTuple":

compiler/sempass2.nim

@@ -168,7 +168,7 @@ proc isRangeSupertype(conf: ConfigRef; wider, narrower: PType): bool =
     # int -> float ranges; warn
     result = false
 
-proc shouldWarnRangeConversion(conf: ConfigRef; formalType, argType: PType): bool =
+proc shouldWarnRangeConversion(conf: ConfigRef; info: TLineInfo; formalType, argType: PType): bool =
   ## Determine if an implicit range conversion should warn
   ## We warn on conversions that are likely to cause panics
   let f = formalType.skipTypes({tyGenericInst, tyAlias, tySink, tyDistinct})
@@ -176,7 +176,19 @@ proc shouldWarnRangeConversion(conf: ConfigRef; formalType, argType: PType): boo
   if f.kind == tyRange:
     # Only warn if formal range doesn't fully contain argument range
     # Check if the ranges don't perfectly overlap
-    result = not isRangeSupertype(conf, f, a)
+    if a.kind == tyInt and f.sym != nil and f.sym.owner != nil and
+        sfSystemModule in f.sym.owner.flags and
+        (f.sym.name.s == "Positive" or
+          f.sym.name.s == "Natural"):
+      # Positive and Natural are special cases that we do not warn on with
+      # ImplicitRangeConversion, but may warn on with systemRangeConversion
+      # if that warning is enabled.
+      if conf.hasWarn(warnSystemRangeConversion):
+        message(conf, info, warnSystemRangeConversion,
+              typeToString(argType) & " -> " & typeToString(formalType))
+      result = false
+    else:
+      result = not isRangeSupertype(conf, f, a)
   else:
     result = false
 
@@ -1538,7 +1550,8 @@ proc track(tracked: PEffects, n: PNode) =
 
     # Check for implicit range conversions
     if n.kind == nkHiddenStdConv and (not tracked.isArrayIndexing) and
-          shouldWarnRangeConversion(tracked.config, n.typ, n[1].typ):
+          n[1].kind notin {nkCharLit..nkUInt64Lit, nkFloatLit..nkFloat128Lit} and
+          shouldWarnRangeConversion(tracked.config, n.info, n.typ, n[1].typ):
       message(tracked.config, n.info, warnImplicitRangeConversion,
               typeToString(n[1].typ) & " -> " & typeToString(n.typ))
 

compiler/semtypes.nim

@@ -1203,7 +1203,15 @@ proc addImplicitGeneric(c: PContext; typeClass: PType, typId: PIdent;
   # is this a bindOnce type class already present in the param list?
   for i in 0..<genericParams.len:
     if genericParams[i].sym.name.id == finalTypId.id:
-      return genericParams[i].typ
+      if typeClass.kind == tyStatic and genericParams[i].typ.kind != tyStatic:
+        # The base type (e.g. from `auto`) was already added as a generic param,
+        # but `static[auto]` requires upgrading it to a `tyStatic` wrapper so
+        # it is instantiated as a compile-time value (`skConst`).
+        genericParams[i].sym.linkTo(typeClass)
+        typeClass.incl tfImplicitTypeParam
+        return typeClass
+      else:
+        return genericParams[i].typ
 
   let owner = if typeClass.sym != nil: typeClass.sym
               else: getCurrOwner(c)
@@ -1739,6 +1747,7 @@ proc semGeneric(c: PContext, n: PNode, s: PSym, prev: PType): PType =
     var isConcrete = true
     let rType = m.call[0].typ
     let mIndex = if rType != nil: rType.len - 1 else: -1
+    var hasForwardTypeParam = false
     for i in 1..<m.call.len:
       var typ = m.call[i].typ
       # is this a 'typedesc' *parameter*? If so, use the typedesc type,
@@ -1755,13 +1764,36 @@ proc semGeneric(c: PContext, n: PNode, s: PSym, prev: PType): PType =
           skip = false
         addToResult(typ, skip)
 
+      if typ.kind == tyForward:
+        hasForwardTypeParam = true
+
     if isConcrete:
       if s.ast == nil and s.typ.kind != tyCompositeTypeClass:
         # XXX: What kind of error is this? is it still relevant?
         localError(c.config, n.info, errCannotInstantiateX % s.name.s)
         result = newOrPrevType(tyError, prev, c)
-      elif containsGenericInvocationWithForward(n[0]):
+      elif containsGenericInvocationWithForward(n[0]) or hasForwardTypeParam:
+        # isConcrete == false means this generic type is not instanciated here because it invoked with generic parameters.
+        # Even if isConcrete == true, don't instanciate it now if there are any `tyForward` type params.
+        # Such `tyForward` type params will be semchecked later and we can instanciate this next time.
+        # Some generic types like std/options.Option[T] needs a type kinds of the given type argument.
+
+        # return `tyForward` instead of `tyGenericInvocation` because:
+        # ```nim
+        #   type Foo = object
+        #     x: Option[Foo]
+        # ```
+        # returning `tyGenericInvocation` makes `Option[Foo]` to `tyGenericInvocation` and
+        # next time `semGeneric` is called with `Option[Foo]`, containsGenericType(typeof(`Foo`)) == true
+        # and `isConcrete == false`.
+        if prev == nil:
+          result = newTypeS(tyForward, c)
+          result.sym = s
+        else:
+          assignType(result, newTypeS(tyForward, c))
+          result.sym = s
         c.forwardTypeUpdates.add (result, n) #fixes 1500
+        return
       else:
         result = instGenericContainer(c, n.info, result,
                                       allowMetaTypes = false)
@@ -2049,7 +2081,9 @@ proc semTypeIdent(c: PContext, n: PNode): PSym =
         # proc signature for example
         if c.inGenericInst > 0:
           let bound = result.typ.elementType.sym
-          if bound != nil: return bound
+          # the symbol may still point to the uninstantiated generic body type 
+          if bound != nil and bound.typ == result.typ.elementType:
+            return bound
           return result
         if result.typ.sym == nil:
           localError(c.config, n.info, errTypeExpected)

compiler/semtypinst.nim

@@ -563,6 +563,26 @@ proc eraseVoidParams*(t: PType) =
       setLen t.n.sons, pos
       break
 
+proc eraseTupleVoidFields*(t: PType) =
+  ## Remove void fields from a named tuple type, compacting both `t.n`
+  ## (the field symbol nodes) and `t.sonsImpl` (the child types).
+  if t.n == nil: return  # anonymous tuple, nothing to compact
+  for i in 0..<t.kidsLen:
+    if t.n[i].kind == nkRecList or t[i].kind == tyVoid:
+      # found first void field, compact from here
+      var pos = i
+      for j in i+1..<t.kidsLen:
+        if t[j].kind != tyVoid and j < t.n.len and t.n[j].kind != nkRecList:
+          t.n[pos] = t.n[j]
+          t[pos] = t[j]
+          if t.n[pos].kind == nkSym:
+            t.n[pos].sym.position = pos
+          inc pos
+        # else: skip void entries
+      setLen t.n.sons, pos
+      t.setSonsLen pos
+      break
+
 proc skipIntLiteralParams*(t: PType; idgen: IdGenerator) =
   for i, p in t.ikids:
     if p == nil: continue
@@ -768,6 +788,8 @@ proc replaceTypeVarsTAux(cl: var TReplTypeVars, t: PType, isInstValue = false):
         propagateFieldFlags(result, result.n)
         if result.kind == tyObject and cl.c.computeRequiresInit(cl.c, result):
           result.incl tfRequiresInit
+        if result.kind == tyTuple:
+          eraseTupleVoidFields(result)
 
       of tyProc:
         eraseVoidParams(result)

compiler/sighashes.nim

@@ -41,6 +41,7 @@ type
     CoType
     CoOwnerSig
     CoIgnoreRange
+    CoIgnoreRangeInArray
     CoConsiderOwned
     CoDistinct
     CoHashTypeInsideNode
@@ -220,10 +221,17 @@ proc hashType(c: var MD5Context, t: PType; flags: set[ConsiderFlag]; conf: Confi
     else:
       for a in t.kids: c.hashType a, flags+{CoIgnoreRange}, conf
   of tyRange:
-    if CoIgnoreRange notin flags:
+    if {CoIgnoreRange, CoIgnoreRangeInArray} * flags == {}:
       c &= char(t.kind)
       c.hashTree(t.n, {}, conf)
-    c.hashType(t.elementType, flags, conf)
+      c.hashType(t.elementType, flags, conf)
+    elif CoIgnoreRangeInArray in flags:
+      # include only the length of the range (not its specific bounds)
+      c &= char(t.kind)
+      let l = lengthOrd(conf, t)
+      lowlevel l
+    else:
+      c.hashType(t.elementType, flags, conf)
   of tyStatic:
     c &= char(t.kind)
     c.hashTree(t.n, {}, conf)
@@ -253,7 +261,7 @@ proc hashType(c: var MD5Context, t: PType; flags: set[ConsiderFlag]; conf: Confi
     if tfVarargs in t.flags: c &= ".varargs"
   of tyArray:
     c &= char(t.kind)
-    c.hashType(t.indexType, flags-{CoIgnoreRange}, conf)
+    c.hashType(t.indexType, flags-{CoIgnoreRange}+{CoIgnoreRangeInArray}, conf)
     c.hashType(t.elementType, flags-{CoIgnoreRange}, conf)
   else:
     c &= char(t.kind)

compiler/sigmatch.nim

@@ -160,8 +160,7 @@ proc matchGenericParam(m: var TCandidate, formal: PType, n: PNode) =
       arg = newTypeS(tyStatic, m.c, son = evaluated.typ)
       arg.n = evaluated
   elif formalBase.kind == tyTypeDesc:
-    if arg.kind != tyTypeDesc:
-      arg = makeTypeDesc(m.c, arg)
+    discard # if arg is not tyTypeDesc, typeRel will report the mismatch
   else:
     arg = arg.skipTypes({tyTypeDesc})
   let tm = typeRel(m, formal, arg)
@@ -2186,9 +2185,9 @@ proc implicitConv(kind: TNodeKind, f: PType, arg: PNode, m: TCandidate,
       result.typ = errorType(c)
   else:
     result.typ = f.skipTypes({tySink})
-  # keep varness
+  # keep varness, but don't wrap lent types with var
   if arg.typ != nil and arg.typ.kind == tyVar:
-    result.typ = toVar(result.typ, tyVar, c.idgen)
+    result.typ = toVar(result.typ.skipTypes({tyLent}), tyVar, c.idgen)
     # copy the tfVarIsPtr flag
     result.typ.flags = arg.typ.flags
   else:

compiler/vmdeps.nim

@@ -62,7 +62,10 @@ proc objectNode(cache: IdentCache; n: PNode; idgen: IdGenerator): PNode =
     result = newNodeI(nkIdentDefs, n.info)
     result.add n  # name
     result.add mapTypeToAstX(cache, n.sym.typ, n.info, idgen, true, false)  # type
-    result.add newNodeI(nkEmpty, n.info)  # no assigned value
+    if n.sym.ast != nil:
+      result.add copyTree(n.sym.ast)
+    else:
+      result.add newNodeI(nkEmpty, n.info)  # no assigned value
   else:
     result = copyNode(n)
     for i in 0..<n.safeLen:
@@ -87,7 +90,10 @@ proc mapTypeToAstX(cache: IdentCache; t: PType; info: TLineInfo;
     var id = newNodeX(nkIdentDefs)
     id.add n  # name
     id.add mapTypeToAst(t, info)  # type
-    id.add newNodeI(nkEmpty, info)  # no assigned value
+    if n.sym.ast != nil:
+      id.add copyTree(n.sym.ast)
+    else:
+      id.add newNodeI(nkEmpty, n.info)  # no assigned value
     id
   template newIdentDefs(s): untyped = newIdentDefs(s, s.typ)
 

doc/manual.md

@@ -1144,6 +1144,8 @@ semantic analysis). Assignments from the base type to one of its subrange types
 A subrange type has the same size as its base type (`int` in the
 Subrange example).
 
+Implicit "downsizing" conversions to range types (for example, `int -> range[0..255]` or `range[1..256] -> range[0..255]`) emit the `ImplicitRangeConversion` warning. Conversions that are clearly safe (for example, `range[0..255] -> range[0..65535]`) and any explicit casts do not trigger this warning. Conversions from `int` to common subranges such as `Natural` or `Positive` do not trigger this warning by default, but can be enabled with `--warning:systemRangeConversion`.
+
 
 Pre-defined floating-point types
 --------------------------------
@@ -7904,7 +7906,7 @@ alignment requirement of the type are ignored.
   main()
   ```
 
-This pragma has no effect on the JS backend.
+This pragma has no effect on the JavaScript backend and may significantly increase memory usage with the `--mm:refc` option.
 
 
 Noalias pragma

doc/manual_experimental.md

@@ -2127,7 +2127,7 @@ can be used in an `isolate` context:
     `=destroy`(dest.value)
   ```
 
-The `.sendable` pragma itself is an experimenal, unchecked, unsafe annotation. It is
+The `.sendable` pragma itself is an experimental, unchecked, unsafe annotation. It is
 currently only used by `Isolated[T]`.
 
 Virtual pragma

doc/markdown_rst.md

@@ -276,9 +276,9 @@ This parser has 2 modes for inline markup:
 
 2) Compatibility mode which is RST rules.
 
-.. Note:: in both modes the parser interpretes text between single
+.. Note:: in both modes the parser interprets text between single
      backticks (code) identically:
-     backslash does not escape; the only exception: ``\`` folowed by `
+     backslash does not escape; the only exception: ``\`` followed by `
      does escape so that we can always input a single backtick ` in
      inline code. However that makes impossible to input code with
      ``\`` at the end in *single* backticks, one must use *double*

doc/nimdoc.css

@@ -123,7 +123,6 @@ Modified by Boyd Greenfield and narimiran
 }
 
 html {
-  overflow-x: hidden;
   max-width: 100%;
   box-sizing: border-box;
   font-size: 100%;
@@ -572,8 +571,8 @@ blockquote.markdown-quote {
   padding-left: 3px;
   padding-right: 3px;
   border-radius: 4px;
-  white-space: normal;
-  word-break: break-all;
+  white-space: pre-wrap;
+  overflow-wrap: break-word;
 }
 
 span.tok {
@@ -674,6 +673,8 @@ table {
   border-collapse: collapse;
   border-color: var(--third-background);
   border-spacing: 0;
+  display: block;
+  overflow-x: auto;
 }
 
 table:not(.line-nums-table) {

doc/nimgrep_cmdline.txt

@@ -52,7 +52,7 @@ Options:
                           nimgrep --filenames               # In current dir
                           nimgrep --filenames "" DIRECTORY
                            # Note empty pattern "", lists all files in DIRECTORY
-* Interprete patterns:
+* Interpret patterns:
   --peg               PATTERN and PAT are Peg
   --re                PATTERN and PAT are regular expressions (default)
   --rex, -x           use the "extended" syntax for the regular expression

doc/packaging.md

@@ -27,7 +27,7 @@ Nim runs on a wide variety of platforms. Support on amd64 and i386 is tested reg
 - ppc64el (aka ppc64le)
 - riscv64
 
-The following platforms are seldomly tested:
+The following platforms are rarely tested:
 
 - alpha
 - hppa

doc/pegdocs.txt

@@ -20,8 +20,8 @@ notation           meaning
                    as they succeed. Indicate success if all succeeded.
                    Otherwise, do not consume any text and indicate failure.
                    The sequence's precedence is higher than that of ordered
-                   choice: ``A B / C`` means ``(A B) / Z`` and
-                   not ``A (B / Z)``.
+                   choice: ``A B / C`` means ``(A B) / C`` and
+                   not ``A (B / C)``.
 ``(E)``            Grouping: Parenthesis can be used to change
                    operator priority.
 ``{E}``            Capture: Apply expression `E` and store the substring

doc/tut1.md

@@ -1159,8 +1159,8 @@ In Nim new types can be defined within a `type` statement:
 
   ```nim  test = "nim c $1"
   type
-    biggestInt = int64      # biggest integer type that is available
-    biggestFloat = float64  # biggest float type that is available
+    BiggestInt = int64      # biggest integer type that is available
+    BiggestFloat = float64  # biggest float type that is available
   ```
 
 Enumeration and object types may only be defined within a

koch.nim

@@ -11,10 +11,10 @@
 
 const
   # examples of possible values for repos: Head, ea82b54
-  NimbleStableCommit = "9207e8b2bbdf66b5a4d1020214cff44d2d30df92"    # 0.20.1
-  AtlasStableCommit = "2aa62121b40d580aa2fb27920a37b938d36c5f57"     # 0.9.4
+  NimbleStableCommit = "aa03f886e4a111d6af9090c6a1f1271d64b66f7b"    # 0.22.2
+  AtlasStableCommit = "ff1f4289482dce94ba9f95b3b0ae16d16e21eb3d"     # 0.10.1
   ChecksumsStableCommit = "0b8e46379c5bc1bf73d8b3011908389c60fb9b98" # 2.0.1
-  SatStableCommit = "faf1617f44d7632ee9601ebc13887644925dcc01"
+  SatStableCommit = "e63eaea8baf00bed8bcd5a29ffd8823abb265b39"
 
   NimonyStableCommit = "deb9b50c573fb55e071825ab55385e293b7216d5" # unversioned \
     # Note that Nimony uses Nim as a git submodule but we don't want to install

lib/core/macros.nim

@@ -433,15 +433,15 @@ when defined(nimHasNoReturnError):
 else:
   {.pragma: errorNoReturn.}
 
-proc error*(msg: string, n: NimNode = nil) {.magic: "NError", benign, errorNoReturn.}
+proc error*(msg: string, n: NimNode = nil) {.magic: "NError", gcsafe, errorNoReturn.}
   ## Writes an error message at compile time. The optional `n: NimNode`
   ## parameter is used as the source for file and line number information in
   ## the compilation error message.
 
-proc warning*(msg: string, n: NimNode = nil) {.magic: "NWarning", benign.}
+proc warning*(msg: string, n: NimNode = nil) {.magic: "NWarning", gcsafe.}
   ## Writes a warning message at compile time.
 
-proc hint*(msg: string, n: NimNode = nil) {.magic: "NHint", benign.}
+proc hint*(msg: string, n: NimNode = nil) {.magic: "NHint", gcsafe.}
   ## Writes a hint message at compile time.
 
 proc newStrLitNode*(s: string): NimNode {.noSideEffect.} =
@@ -511,7 +511,7 @@ proc genSym*(kind: NimSymKind = nskLet; ident = ""): NimNode {.
   ## Generates a fresh symbol that is guaranteed to be unique. The symbol
   ## needs to occur in a declaration context.
 
-proc callsite*(): NimNode {.magic: "NCallSite", benign, deprecated:
+proc callsite*(): NimNode {.magic: "NCallSite", gcsafe, deprecated:
   "Deprecated since v0.18.1; use `varargs[untyped]` in the macro prototype instead".}
   ## Returns the AST of the invocation expression that invoked this macro.
   # see https://github.com/nim-lang/RFCs/issues/387 as candidate replacement.
@@ -933,7 +933,7 @@ proc eqIdent*(a: NimNode; b: NimNode): bool {.magic: "EqIdent", noSideEffect.}
 
 const collapseSymChoice = not defined(nimLegacyMacrosCollapseSymChoice)
 
-proc treeTraverse(n: NimNode; res: var string; level = 0; isLisp = false, indented = false) {.benign.} =
+proc treeTraverse(n: NimNode; res: var string; level = 0; isLisp = false, indented = false) {.gcsafe.} =
   if level > 0:
     if indented:
       res.add("\n")
@@ -982,21 +982,21 @@ proc treeTraverse(n: NimNode; res: var string; level = 0; isLisp = false, indent
   if isLisp:
     res.add(")")
 
-proc treeRepr*(n: NimNode): string {.benign.} =
+proc treeRepr*(n: NimNode): string {.gcsafe.} =
   ## Convert the AST `n` to a human-readable tree-like string.
   ##
   ## See also `repr`, `lispRepr`_, and `astGenRepr`_.
   result = ""
   n.treeTraverse(result, isLisp = false, indented = true)
 
-proc lispRepr*(n: NimNode; indented = false): string {.benign.} =
+proc lispRepr*(n: NimNode; indented = false): string {.gcsafe.} =
   ## Convert the AST `n` to a human-readable lisp-like string.
   ##
   ## See also `repr`, `treeRepr`_, and `astGenRepr`_.
   result = ""
   n.treeTraverse(result, isLisp = true, indented = indented)
 
-proc astGenRepr*(n: NimNode): string {.benign.} =
+proc astGenRepr*(n: NimNode): string {.gcsafe.} =
   ## Convert the AST `n` to the code required to generate that AST.
   ##
   ## See also `repr`_, `treeRepr`_, and `lispRepr`_.
@@ -1005,7 +1005,7 @@ proc astGenRepr*(n: NimNode): string {.benign.} =
     NodeKinds = {nnkEmpty, nnkIdent, nnkSym, nnkNone, nnkCommentStmt}
     LitKinds = {nnkCharLit..nnkInt64Lit, nnkFloatLit..nnkFloat64Lit, nnkStrLit..nnkTripleStrLit}
 
-  proc traverse(res: var string, level: int, n: NimNode) {.benign.} =
+  proc traverse(res: var string, level: int, n: NimNode) {.gcsafe.} =
     for i in 0..level-1: res.add "  "
     if n.kind in NodeKinds:
       res.add("new" & ($n.kind).substr(3) & "Node(")

lib/impure/nre/private/util.nim

@@ -15,6 +15,9 @@ template formatStr*(howExpr, namegetter, idgetter): untyped =
       val.add(how[i])
       i += 1
     else:
+      if i + 1 >= how.len:
+        raise newException(ValueError, "Syntax error in format string at " & $i)
+
       if how[i + 1] == '$':
         val.add('$')
         i += 2
@@ -27,7 +30,7 @@ template formatStr*(howExpr, namegetter, idgetter): untyped =
         i += 1
         var id {.inject.} = 0
         while i < how.len and how[i] in {'0'..'9'}:
-          id += (id * 10) + (ord(how[i]) - ord('0'))
+          id = (id * 10) + (ord(how[i]) - ord('0'))
           i += 1
         val.add(idgetter)
         lastNum = id + 1
@@ -44,6 +47,8 @@ template formatStr*(howExpr, namegetter, idgetter): untyped =
         while i < how.len and how[i] != '}':
           name.add(how[i])
           i += 1
+        if i >= how.len or how[i] != '}':
+          raise newException(ValueError, "Syntax error in format string at " & $i)
         i += 1
         val.add(namegetter)
       else:

lib/packages/docutils/highlite.nim

@@ -326,7 +326,8 @@ proc nimNextToken(g: var GeneralTokenizer, keywords: openArray[string] = @[]) =
       pos = nimNumber(g, pos)
     of '\'':
       inc(pos)
-      if g.kind != gtPunctuation:
+      let followsBacktick = pos >= 2 and g.buf[pos - 2] == '`'
+      if not followsBacktick:
         g.kind = gtCharLit
         while true:
           case g.buf[pos]
@@ -338,6 +339,8 @@ proc nimNextToken(g: var GeneralTokenizer, keywords: openArray[string] = @[]) =
           of '\\':
             inc(pos, 2)
           else: inc(pos)
+      else:
+        g.kind = gtPunctuation
     of '\"':
       inc(pos)
       if (g.buf[pos] == '\"') and (g.buf[pos + 1] == '\"'):

lib/pure/asyncdispatch.nim

@@ -1946,9 +1946,14 @@ proc withTimeout*[T](fut: Future[T], timeout: int): owned(Future[bool]) =
           retFuture.fail(fut.error)
         else:
           retFuture.complete(true)
+        # Timeout side lost; drop its callback to avoid retaining closures/futures.
+        timeoutFuture.clearCallbacks()
   timeoutFuture.callback =
     proc () =
-      if not retFuture.finished: retFuture.complete(false)
+      if not retFuture.finished:
+        retFuture.complete(false)
+        # Wrapped future side lost; drop its callback to avoid retaining closures/futures.
+        fut.clearCallbacks()
   return retFuture
 
 proc accept*(socket: AsyncFD,

lib/pure/base64.nim

@@ -255,6 +255,9 @@ proc decode*(s: string): string =
   while inputIndex <= inputEnds:
     while s[inputIndex] in {'\n', '\r', ' '}:
       inc inputIndex
+    # double check inputIndex as it can be incremented due to whitespace
+    if inputIndex > inputEnds:
+      break
     inputChar(a)
     inputChar(b)
     inputChar(c)

lib/pure/parseopt.nim

@@ -14,149 +14,306 @@
 ## Supported Syntax
 ## ================
 ##
-## The following syntax is supported when arguments for the `shortNoVal` and
-## `longNoVal` parameters, which are
-## `described later<#nimshortnoval-and-nimlongnoval>`_, are not provided:
+## The syntax described here applies to the default way the parser works.
+## The behavior is configurable, though, and two additional modes
+## are supported, see the details: `Parser Modes`_.
 ##
-## 1. Short options: `-abcd`, `-e:5`, `-e=5`
+## Parsing also depends on whether the `shortNoVal` and `longNoVal` parameters
+## are omitted/empty or provided. The details are described in a
+## `later section<#nimshortnoval-and-nimlongnoval>`_.
+##
+## The following syntax is supported:
+##
+## 1. Short options: `-a:5`, `-b=5`, `-cde`, `-fgh=5`
 ## 2. Long options: `--foo:bar`, `--foo=bar`, `--foo`
 ## 3. Arguments: everything that does not start with a `-`
 ##
-## These three kinds of tokens are enumerated in the
-## `CmdLineKind enum<#CmdLineKind>`_.
+## Passing values to options **requires** a separator (`:`/`=`), short options
+## (flags) can be bundled together and the last one can take a value.
 ##
-## When option values begin with ':' or '=', they need to be doubled up (as in
-## `--delim::`) or alternated (as in `--delim=:`).
+## Option values can begin with the separator character (`:`/`=`), so all of the
+## following is valid:
+##   - option `foo`, value `:`:  `--foo::`, `--foo=:`
+##   - option `foo`, value `=`:  `--foo:=`, `--foo==`
 ##
 ## The `--` option, commonly used to denote that every token that follows is
 ## an argument, is interpreted as a long option, and its name is the empty
-## string.
+## string. Trailing arguments can be accessed with `remainingArgs<#remainingArgs,OptParser>`_
+## or `cmdLineRest<#cmdLineRest,OptParser>`_.
 ##
 ## Parsing
 ## =======
 ##
-## Use an `OptParser<#OptParser>`_ to parse command line options. It can be
-## created with `initOptParser<#initOptParser,string,set[char],seq[string]>`_,
-## and `next<#next,OptParser>`_ advances the parser by one token.
+## To parse command line options, use the `getopt iterator<#getopt.i,OptParser>`_.
+## It initializes the `OptParser<#OptParser>`_ object internally and iterates
+## through the command line options.
 ##
-## For each token, the parser's `kind`, `key`, and `val` fields give
-## information about that token. If the token is a long or short option, `key`
-## is the option's name, and  `val` is either the option's value, if provided,
-## or the empty string. For arguments, the `key` field contains the argument
-## itself, and `val` is unused. To check if the end of the command line has
-## been reached, check if `kind` is equal to `cmdEnd`.
+## For each token, the parser's `kind` (`CmdLineKind enum<#CmdLineKind>`_.),
+## `key`, and `val` fields are yielded.
+##
+## For long and short options, `key` is the option's name, and `val` is either
+## the option's value, if given, or an empty string. For arguments, the `key`
+## field contains the argument itself, and `val` is unused (empty).
 ##
 ## Here is an example:
 ##
-##   ```Nim
-##   import std/parseopt
+runnableExamples:
+  import std/os
+
+  let cmds = "-ab -e:5 --foo --bar=20 file.txt".parseCmdLine()
+  var output: seq[string] = @[]
+  # If cmds is not supplied, real arguments will be retrieved by the `os` module
+  for kind, key, val in getopt(cmds):
+    case kind
+    of cmdEnd: break
+    of cmdShortOption, cmdLongOption:
+      if val == "":
+        output.add("Option: " & key)
+      else:
+        output.add("Option and value: " & key & ", " & val)
+    of cmdArgument:
+      output.add("Argument: " & key)
+
+  doAssert output == @[
+    "Option: a",
+    "Option: b",
+    "Option and value: e, 5",
+    "Option: foo",
+    "Option and value: bar, 20",
+    "Argument: file.txt"
+  ]
 ##
-##   var p = initOptParser("-ab -e:5 --foo --bar=20 file.txt")
-##   while true:
-##     p.next()
-##     case p.kind
-##     of cmdEnd: break
-##     of cmdShortOption, cmdLongOption:
-##       if p.val == "":
-##         echo "Option: ", p.key
-##       else:
-##         echo "Option and value: ", p.key, ", ", p.val
-##     of cmdArgument:
-##       echo "Argument: ", p.key
+## The `OptParser<#OptParser>`_ can be initialized with
+## `initOptParser<#initOptParser,string,set[char],seq[string]>`_.
+## The `next<#next,OptParser>`_ proc advances the parser by one token.
 ##
-##   # Output:
-##   # Option: a
-##   # Option: b
-##   # Option and value: e, 5
-##   # Option: foo
-##   # Option and value: bar, 20
-##   # Argument: file.txt
-##   ```
+## When iterating the object manually with `next<#next,OptParser>`_, reaching
+## the end of the command line is signalled by setting the `kind` field
+## to `cmdEnd`.
 ##
-## The `getopt iterator<#getopt.i,OptParser>`_, which is provided for
-## convenience, can be used to iterate through all command line options as well.
+## To set a default value for an option, assign the default value to a variable
+## beforehand, then update it while parsing.
 ##
-## To set a default value for a variable assigned through `getopt` and accept arguments from the cmd line.
-## Assign the default value to a variable before parsing.
-## Then set the variable to the new value while parsing.
-##
-## Here is an example:
-##
-##   ```Nim
-##   import std/parseopt
-##
-##   var varName: string = "defaultValue"
-##
-##   for kind, key, val in getopt():
-##     case kind
-##     of cmdArgument:
-##       discard
-##     of cmdLongOption, cmdShortOption:
-##       case key:
-##       of "varName": # --varName:<value> in the console when executing
-##         varName = val # do input sanitization in production systems
-##     of cmdEnd:
-##       discard
-##   ```
+runnableExamples:
+  import std/strutils
+
+  var varName: string = "defaultValue"
+
+  for kind, key, val in getopt(@["--varName:HELLO"]):
+    case kind
+    of cmdArgument:
+      discard
+    of cmdLongOption, cmdShortOption:
+      case key
+      of "varName":  # --varName:<value> in the console when executing
+        varName = val.toLowerAscii() # do input sanitization in production
+    of cmdEnd:
+      discard
+
+  doAssert varName == "hello"
 ##
 ## `shortNoVal` and `longNoVal`
 ## ============================
 ##
-## The optional `shortNoVal` and `longNoVal` parameters present in
-## `initOptParser<#initOptParser,string,set[char],seq[string]>`_ are for
+## The optional `shortNoVal` and `longNoVal` parameters in
+## `initOptParser<#initOptParser,string,set[char],seq[string]>`_ and
+## `getopt iterator<#getopt.i,OptParser>`_ are for
 ## specifying which short and long options do not accept values.
 ##
-## When `shortNoVal` is non-empty, users are not required to separate short
-## options and their values with a ':' or '=' since the parser knows which
-## options accept values and which ones do not. This behavior also applies for
-## long options if `longNoVal` is non-empty. For short options, `-j4`
-## becomes supported syntax, and for long options, `--foo bar` becomes
-## supported. This is in addition to the `previously mentioned
-## syntax<#supported-syntax>`_. Users can still separate options and their
-## values with ':' or '=', but that becomes optional.
+## When `shortNoVal` or `longNoVal` is non-empty, using the separators (`:`/`=`)
+## becomes non-mandatory and users can separate a value from long
+## options (that are not supplied to the corresponding argument) by whitespace
+## or, in the case of a short option, by writing the value directly adjacent to
+## the option.
+##
+## For short options, `-j4` becomes supported syntax (parsed as option `j` with
+## value `4` instead of two separate options `j` and `4`). For long options,
+## `--foo bar` becomes supported syntax in all `modes<Parser Modes>`_.
+##
+## In `LaxMode` and `GnuMode`, short options can also take values from the next
+## argument (`-c val`), but this does **not** work in the default `Nim` mode.
 ##
 ## As more options which do not accept values are added to your program,
 ## remember to amend `shortNoVal` and `longNoVal` accordingly.
 ##
+## The parser does not validate the input for syntax mistakes, thus, options
+## can still have values if passed explicitly by the user, even when they are
+## marked as `shortNoVal`/`longNoVal`.
+##
+## This behavior allows associating an option with the mistakenly passed value:
+##
+runnableExamples:
+  import std/[sequtils, os]
+
+  let cmds = "-n:9 --foo:bar".parseCmdLine()
+  let parsed = toSeq(cmds.getopt(shortNoVal = {'n'}, longNoVal = @["foo"]))
+  for (kind, key, val) in parsed:
+   case kind
+   of cmdEnd: raise newException(AssertionDefect, "Unreachable")
+   of cmdShortOption, cmdLongOption:
+     if key in ["n", "foo"] and val != "":
+       # Substitute for proper error handling in your code
+       discard "Option " & key & " can't take values!"
+     else: discard
+   of cmdArgument: discard
+  doAssert parsed == @[
+   (cmdShortOption, "n", "9"),
+   (cmdLongOption, "foo", "bar")]
+##
+## .. Important::
+##   Next-argument value-taking for short/long options is only enabled when
+##   `shortNoVal`/`longNoVal` are non-empty. If your program has *no* options
+##   that take no value, you still must pass a non-empty placeholder (for example,
+##   `shortNoVal = {'\0'}` and/or `longNoVal = @[""]`) to enable this form.
+##
 ## The following example illustrates the difference between having an empty
 ## `shortNoVal` and `longNoVal`, which is the default, and providing
 ## arguments for those two parameters:
 ##
-##   ```Nim
-##   import std/parseopt
+runnableExamples:
+
+  proc format(kind: CmdLineKind; key, val: string): string =
+    case kind
+    of cmdEnd: raise newException(AssertionDefect, "Unreachable")
+    of cmdShortOption, cmdLongOption:
+      if val == "": "Option: " & key
+      else:         "Option and value: " & key & ", " & val
+    of cmdArgument: "Argument: " & key
+
+  let cmdLine = "-j4 --first bar"
+  var output1, output2: seq[string] = @[]
+
+  var emptyNoVal = initOptParser(cmdLine)
+  for kind, key, val in emptyNoVal.getopt():
+    output1.add format(kind, key, val)
+
+  doAssert output1 == @[
+    "Option: j",
+    "Option: 4",
+    "Option: first",
+    "Argument: bar"
+  ]
+
+  var withNoVal = cmdLine.initOptParser(shortNoVal = {'c'},
+                                  longNoVal = @["second"])
+  for kind, key, val in withNoVal.getopt():
+    output2.add format(kind, key, val)
+
+  doAssert output2 == @[
+    "Option and value: j, 4",
+    "Option and value: first, bar"
+  ]
 ##
-##   proc printToken(kind: CmdLineKind, key: string, val: string) =
-##     case kind
-##     of cmdEnd: doAssert(false)  # Doesn't happen with getopt()
-##     of cmdShortOption, cmdLongOption:
-##       if val == "":
-##         echo "Option: ", key
-##       else:
-##         echo "Option and value: ", key, ", ", val
-##     of cmdArgument:
-##       echo "Argument: ", key
+## Parser Modes
+## ============
 ##
-##   let cmdLine = "-j4 --first bar"
+## .. Warning:: Modes other than the default (`Nim`) are **experimental** and may
+##    change in future releases.
 ##
-##   var emptyNoVal = initOptParser(cmdLine)
-##   for kind, key, val in emptyNoVal.getopt():
-##     printToken(kind, key, val)
+## The parser supports several distinct rule sets that change how options are
+## interpreted:
 ##
-##   # Output:
-##   # Option: j
-##   # Option: 4
-##   # Option: first
-##   # Argument: bar
+## 1. **LaxMode**: Most forgiving mode, combines `Nim` with POSIX-like
+##    short option handling. Tries to follow the POSIX_ guidelines where possible.
+## 2. **NimMode**: Standard Nim parsing rules (default).
+## 3. **GnuMode**: GNU-inspired parsing (e.g. `=` as the only delimiter).
+##    Puts some additional restrictions, following some of the GNU_ conventions.
 ##
-##   var withNoVal = initOptParser(cmdLine, shortNoVal = {'c'},
-##                                 longNoVal = @["second"])
-##   for kind, key, val in withNoVal.getopt():
-##     printToken(kind, key, val)
+## Modes are ordered from most relaxed to strictest. The names were
+## chosen to set general user expectations and full compliance is neither
+## achieved nor planned.
 ##
-##   # Output:
-##   # Option and value: j, 4
-##   # Option and value: first, bar
-##   ```
+## Mode Differences
+## ----------------
+##
+## **NimMode** (default):
+##
+## - Short options require adjacent values or explicit delimiters:
+##   `-cval`, `-c:val`, `-c=val`
+## - Short options follow POSIX-style bundling rules
+## - Next-argument value taking (`-c val`) is **not** supported by default
+## - Supports both `:` and `=` as delimiters
+## - Allows whitespace around delimiters
+## - Values starting with `-` are interpreted as new options
+##
+## **LaxMode**:
+##
+## - Essentially the Nim mode with some relaxations for short options:
+##   + Allows short options to take values from the next argument: `-c val`
+##   + Supports bundled short options with trailing value: `-abc val`
+## - Values starting with `-` can be consumed as option arguments
+##
+## **GnuMode**:
+##
+## - Only `=` is treated as a delimiter (`:` is not a delimiter)
+## - No whitespace allowed around `=`
+## - Short options can take next-argument values (`-c val`), but only whitespace
+##   is allowed as a delimiter, separators parse as part of the value
+## - Short options follow POSIX-style bundling rules
+## - Values starting with `-` can be consumed as option arguments
+## - Known discrepancies compared to GNU getopt:
+##   + No notion of optional/mandatory arguments, colon (`:`) doesn't
+##     indicate them and overall is not a special character.
+##
+## Mode-Specific Behavior
+## ----------------------
+##
+## The parser's behavior varies significantly between modes, particularly
+## around how options consume their values:
+##
+## **Short Options**
+##
+## Consider `-c val`:
+##
+## - In `Nim` mode: `-c` is parsed as an option without a value, and `val` is
+##   parsed as a separate argument, regardless of `shortNoVal` being empty or not.
+## - In `Lax` and `Gnu` modes:
+##   + When `shortNoVal` is empty, or not empty and `-c` is in it:
+##     Same as `Nim`, parsed as option `-c` followed by argument `val`.
+##   + When `-c` is not in `shortNoVal`:
+##     parsed as option `-c`, `val` is consumed as its value.
+##
+## Consider `-c-10`:
+##
+## - If `shortNoVal` value is empty, all three modes parse three separate short
+##   options: `c`, `1` and `0`.
+## - Otherwise, if `-c` is not in `shortNoVal`:
+##   + `Nim`: `-c` is an option without an argument. `-10` is interpreted as a
+##      an option `-1` with the `0` argument.
+##   + `Lax` and `Gnu` modes: `-10` is consumed as the value of `-c`
+##     (allowing negative number values).
+##
+## **Long Options**
+##
+## Consider `--foo:bar`:
+##
+## - `Nim`: `:` is a valid delimiter, so `bar` is the value of `--foo`.
+## - `LaxMode`: same as `Nim`.
+## - `Gnu`: only `=` is a valid delimiter, so this parses as an option named
+##   `foo:bar` without a value (unless `longNoVal` is non-empty and allows
+##   next-argument consumption).
+##
+## Consider `--foo =bar`:
+##
+## - `Nim`: whitespace around delimiters is allowed, so `=bar` is the
+##   value of `--foo`.
+## - `LaxMode`: same as `Nim`.
+## - `Gnu`: whitespace around `=` is not allowed, so `--foo` is an
+##   option without a value, and `=bar` is parsed as an argument.
+##
+## Custom Rule Sets
+## ================
+##
+## .. Warning:: Custom rule sets are unsupported and not tested
+##
+## If you require parsing rules beyond the three provided modes, it's possible
+## to define a custom parser behavior by specifying a set of individual parser
+## rules.
+##
+## Due to this feature being unsupported, it requires importing the private
+## symbols of the module (with `import std/parseopt {.all.}`) and utilizing
+## the unexported `initOptParser` overload, which accepts `set[ParserRules]`
+## (see the `ParserRules` enum in the code for details).
 ##
 ## See also
 ## ========
@@ -171,13 +328,42 @@
 ##   parser
 ## * `parsexml module<parsexml.html>`_ for a XML / HTML parser
 ## * `other parsers<lib.html#pure-libraries-parsers>`_ for more parsers
+## * POSIX_ - The Open Group Base Specifications Issue 8. Utility Conventions
+## * GNU_ - GNU C Library reference manual. 26.1.1 Program Argument Syntax Conventions
+##
+## .. _GNU: https://sourceware.org/glibc/manual/latest/html_node/Argument-Syntax.html
+## .. _POSIX: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap12.html
 
 {.push debugger: off.}
 
 include "system/inclrtl"
 
-import std/strutils
 import std/os
+when defined(nimscript):
+  from std/strutils import toLowerAscii, endsWith
+
+type
+  CliMode* = enum
+    ## Parser behavior profiles used to control parser behavior.
+    ## See `Parser Modes`_ for details.
+    LaxMode, ## The most forgiving mode
+    NimMode, ## Nim parsing rules (default)
+    GnuMode ## GNU-style parsing
+
+type
+  ParserRules = enum
+    ## Feature flags used to assemble parser behavior for a given mode.
+    prSepAllowDelimBefore,       ## Allow whitespace before an opt-val separator
+    prSepAllowDelimAfter,        ## Allow whitespace after an opt-val separator
+    prShortAllowSep,             ## Allow `-k<separator>val` form
+    prShortBundle,               ## Allow bundling short options behind one '-'
+    prShortValAllowAdjacent,     ## Allow adjacent short option values: `-kval`
+    prShortValAllowNextArg,      ## Allow next-argv short option values: `-k val`
+    prShortValAllowDashLeading,  ## Allow values that start with '-' to be taken
+    prLongAllowSep,              ## Allow `--opt<separator>val` form
+    prLongValAllowNextArg,       ## Allow `--opt val` form, requires non-empty `longNoVal`
+    prSepAllowColon,             ## Allow `:` as an opt-val separator
+    prSepAllowEq,                ## Allow `=` as an opt-val separator
 
 type
   CmdLineKind* = enum ## The detected command line token.
@@ -189,21 +375,51 @@ type
     ## Implementation of the command line parser.
     ##
     ## To initialize it, use the
-    ## `initOptParser proc<#initOptParser,string,set[char],seq[string]>`_.
+    ## `initOptParser proc<#initOptParser,string,set[char],seq[string],CliMode>`_.
+    ## `next<#next,OptParser>`_ is used to advance the parser state and move
+    ## through the parsed tokens.
     pos: int
     inShortState: bool
-    allowWhitespaceAfterColon: bool
     shortNoVal: set[char]
     longNoVal: seq[string]
     cmds: seq[string]
     idx: int
+    separators: set[char]        ## Allowed separators for long/short option values
+    rules: set[ParserRules]
     kind*: CmdLineKind           ## The detected command line token
     key*, val*: string           ## Key and value pair; the key is the option
                                  ## or the argument, and the value is not "" if
                                  ## the option was given a value
 
+const DelimSet = {'\t', ' '} ## Allowed delimiters between tokens
+
+func toRules(m: CliMode): set[ParserRules] =
+  ## Default rule sets for the given mode `m`
+  let
+    Common = {
+      prSepAllowEq,
+      prShortValAllowAdjacent,
+      prShortBundle,
+      prLongValAllowNextArg,
+      prLongAllowSep,
+    }
+    Lax = {
+      prSepAllowColon,
+      prSepAllowDelimBefore,
+      prSepAllowDelimAfter,
+      prShortAllowSep,
+    }
+    ShortPosix = {
+      prShortValAllowNextArg,
+      prShortValAllowDashLeading,
+    }
+  case m
+  of LaxMode: Common + Lax + ShortPosix
+  of NimMode: Common + Lax
+  of GnuMode: Common + ShortPosix
+
 proc parseWord(s: string, i: int, w: var string,
-               delim: set[char] = {'\t', ' '}): int =
+               delim: set[char] = DelimSet): int =
   result = i
   if result < s.len and s[result] == '\"':
     inc(result)
@@ -218,34 +434,23 @@ proc parseWord(s: string, i: int, w: var string,
       add(w, s[result])
       inc(result)
 
-proc initOptParser*(cmdline: seq[string], shortNoVal: set[char] = {},
-                    longNoVal: seq[string] = @[];
-                    allowWhitespaceAfterColon = true): OptParser =
-  ## Initializes the command line parser.
-  ##
-  ## If `cmdline.len == 0`, the real command line as provided by the
-  ## `os` module is retrieved instead if it is available. If the
-  ## command line is not available, a `ValueError` will be raised.
-  ## Behavior of the other parameters remains the same as in
-  ## `initOptParser(string, ...)
-  ## <#initOptParser,string,set[char],seq[string]>`_.
-  ##
-  ## See also:
-  ## * `getopt iterator<#getopt.i,seq[string],set[char],seq[string]>`_
-  runnableExamples:
-    var p = initOptParser()
-    p = initOptParser(@["--left", "--debug:3", "-l", "-r:2"])
-    p = initOptParser(@["--left", "--debug:3", "-l", "-r:2"],
-                      shortNoVal = {'l'}, longNoVal = @["left"])
-  result = OptParser(pos: 0, idx: 0, inShortState: false,
-                    shortNoVal: shortNoVal, longNoVal: longNoVal,
-                    allowWhitespaceAfterColon: allowWhitespaceAfterColon
+proc initOptParser(cmdline: openArray[string];
+                    shortNoVal: set[char];
+                    longNoVal: seq[string];
+                    rules: set[ParserRules]): OptParser =
+  result = OptParser(pos: 0, idx: 0,
+                    cmds: @cmdline,
+                    inShortState: false,
+                    shortNoVal: shortNoVal,
+                    longNoVal: longNoVal,
+                    separators: {},
+                    rules: rules,
+                    kind: cmdEnd,
+                    key: "", val: "",
                     )
-  if cmdline.len != 0:
-    result.cmds = newSeq[string](cmdline.len)
-    for i in 0..<cmdline.len:
-      result.cmds[i] = cmdline[i]
-  else:
+  if prSepAllowEq    in rules: result.separators.incl('=')
+  if prSepAllowColon in rules: result.separators.incl(':')
+  if cmdline.len == 0:
     when declared(paramCount):
       when defined(nimscript):
         var ctr = 0
@@ -254,7 +459,7 @@ proc initOptParser*(cmdline: seq[string], shortNoVal: set[char] = {},
           if firstNimsFound: 
             result.cmds[ctr] = paramStr(i)
             inc ctr, 1
-          if paramStr(i).endsWith(".nims") and not firstNimsFound:
+          if paramStr(i).toLowerAscii().endsWith(".nims") and not firstNimsFound:
             firstNimsFound = true 
             result.cmds = newSeq[string](paramCount()-i)
       else:
@@ -266,25 +471,73 @@ proc initOptParser*(cmdline: seq[string], shortNoVal: set[char] = {},
       # access the command line arguments then!
       raiseAssert "empty command line given but" &
         " real command line is not accessible"
-  result.kind = cmdEnd
-  result.key = ""
-  result.val = ""
 
-proc initOptParser*(cmdline = "", shortNoVal: set[char] = {},
+proc initOptParser*(cmdline: seq[string];
+                    shortNoVal: set[char] = {};
                     longNoVal: seq[string] = @[];
-                    allowWhitespaceAfterColon = true): OptParser =
+                    mode: CliMode = NimMode): OptParser =
   ## Initializes the command line parser.
   ##
-  ## If `cmdline == ""`, the real command line as provided by the
-  ## `os` module is retrieved instead if it is available. If the
-  ## command line is not available, a `ValueError` will be raised.
+  ## **Parameters:**
   ##
-  ## `shortNoVal` and `longNoVal` are used to specify which options
-  ## do not take values. See the `documentation about these
-  ## parameters<#nimshortnoval-and-nimlongnoval>`_ for more information on
-  ## how this affects parsing.
+  ## - `cmdline`: Sequence of command line arguments to parse. If empty, the
+  ##   real command line as provided by the `os` module is retrieved instead.
+  ##   If the command line is not available, an assertion will be raised.
+  ## - `shortNoVal`: Set of short option characters that do not accept values.
+  ##   See `shortNoVal and longNoVal<#nimshortnoval-and-nimlongnoval>`_ for details.
+  ## - `longNoVal`: Sequence of long option names that do not accept values.
+  ##   See `shortNoVal and longNoVal<#nimshortnoval-and-nimlongnoval>`_ for details.
+  ## - `mode`: Parser behavior profile (`NimMode`, `LaxMode`, or `GnuMode`).
+  ##   See `Parser Modes`_ for details.
   ##
-  ## This does not provide a way of passing default values to arguments.
+  ## See also:
+  ## * `getopt iterator<#getopt.i,seq[string],set[char],seq[string],CliMode>`_
+  runnableExamples:
+    var p = initOptParser()
+    p = initOptParser(@["--left", "--debug:3", "-l", "-r:2"])
+    p = initOptParser(@["--left", "--debug:3", "-l", "-r:2"],
+                      shortNoVal = {'l'}, longNoVal = @["left"])
+  initOptParser(cmdline, shortNoVal, longNoVal, toRules(mode))
+
+proc initOptParser*(cmdline: seq[string],
+                    shortNoVal: set[char] = {},
+                    longNoVal: seq[string] = @[];
+                    allowWhitespaceAfterColon: bool): OptParser {.deprecated:
+      "`allowWhitespaceAfterColon` is deprecated, use parser modes instead".} =
+  ## This is an overload for continued support of the legacy `allowWhitespaceAfterColon`
+  ## option. It modifies the default parser mode so that the passed value is respected.
+  ##
+  ## Current default parser mode behaves as if `true` was passed (old default)
+  ##
+  ## - `allowWhitespaceAfterColon`: When `true`, allows forms like
+  ##   `--option: value` or `--option= value` where the value is in the next
+  ##   token after the delimiter. When `false`, the value must be in the same
+  ##   token as the delimiter.
+  var nimrules = toRules(NimMode)
+  if allowWhitespaceAfterColon == false: nimrules.excl prSepAllowDelimAfter
+  initOptParser(cmdline, shortNoVal, longNoVal, nimrules)
+
+proc initOptParser*(cmdline = "";
+                    shortNoVal: set[char] = {};
+                    longNoVal: seq[string] = @[];
+                    mode: CliMode = NimMode): OptParser =
+  ## Initializes the command line parser from a command line string.
+  ##
+  ## The `cmdline` string is parsed into tokens using shell-like quoting rules.
+  ##
+  ## **Parameters:**
+  ##
+  ## - `cmdline`: Command line string to parse. If empty, the real command line
+  ##   as provided by the `os` module is retrieved instead. If the command line
+  ##   is not available, an assertion will be raised.
+  ## - `shortNoVal`: Set of short option characters that do not accept values.
+  ##   See `shortNoVal and longNoVal<#nimshortnoval-and-nimlongnoval>`_ for details.
+  ## - `longNoVal`: Sequence of long option names that do not accept values.
+  ##   See `shortNoVal and longNoVal<#nimshortnoval-and-nimlongnoval>`_ for details.
+  ## - `mode`: Parser behavior profile (`NimMode`, `LaxMode`, or `GnuMode`).
+  ##   See `Parser Modes`_ for details.
+  ##
+  ## **Note:** This does not provide a way of passing default values to arguments.
   ##
   ## See also:
   ## * `getopt iterator<#getopt.i,OptParser>`_
@@ -293,34 +546,81 @@ proc initOptParser*(cmdline = "", shortNoVal: set[char] = {},
     p = initOptParser("--left --debug:3 -l -r:2")
     p = initOptParser("--left --debug:3 -l -r:2",
                       shortNoVal = {'l'}, longNoVal = @["left"])
+  initOptParser(parseCmdLine(cmdline), shortNoVal, longNoVal, toRules(mode))
 
-  initOptParser(parseCmdLine(cmdline), shortNoVal, longNoVal, allowWhitespaceAfterColon)
+proc initOptParser*(cmdline = "";
+                    shortNoVal: set[char] = {};
+                    longNoVal: seq[string] = @[];
+                    allowWhitespaceAfterColon: bool): OptParser {.deprecated:
+      "`allowWhitespaceAfterColon` is deprecated, use parser modes instead".} =
+  ## This is an overload for continued support of the legacy `allowWhitespaceAfterColon`
+  ## option. It modifies the default parser mode so that the passed value is respected.
+  ##
+  ## Current default parser mode behaves as if `true` was passed (old default).
+  ##
+  ## - `allowWhitespaceAfterColon`: When `true`, allows forms like
+  ##   `--option: value` or `--option= value` where the value is in the next
+  ##   token after the delimiter. When `false`, the value must be in the same
+  ##   token as the delimiter.
+  var nimrules = toRules(NimMode)
+  if allowWhitespaceAfterColon == false: nimrules.excl prSepAllowDelimAfter
+  initOptParser(parseCmdLine(cmdline), shortNoVal, longNoVal, nimrules)
 
 proc handleShortOption(p: var OptParser; cmd: string) =
   var i = p.pos
   p.kind = cmdShortOption
-  if i < cmd.len:
+  if i < cmd.len: # multidigit short option support goes here
     add(p.key, cmd[i])
     inc(i)
   p.inShortState = true
-  while i < cmd.len and cmd[i] in {'\t', ' '}:
-    inc(i)
-    p.inShortState = false
-  if i < cmd.len and (cmd[i] in {':', '='} or
-      card(p.shortNoVal) > 0 and p.key[0] notin p.shortNoVal):
-    if i < cmd.len and cmd[i] in {':', '='}:
+  if prSepAllowDelimBefore in p.rules:
+    while i < cmd.len and cmd[i] in DelimSet:
       inc(i)
+      p.inShortState = false
+
+  proc consumeDelims() =
+    while i < cmd.len and cmd[i] in DelimSet: inc(i)
+
+  proc advance(p: var OptParser; n = 1)=
     p.inShortState = false
-    while i < cmd.len and cmd[i] in {'\t', ' '}: inc(i)
+    p.pos = 0
+    inc p.idx, n
+    
+  template next(): untyped = p.cmds[p.idx + 1]
+
+  let canTakeVal = card(p.shortNoVal) > 0 and p.key[0] notin p.shortNoVal 
+  if i < cmd.len and cmd[i] in p.separators:
+    # separator case
+    if prShortAllowSep in p.rules:
+      # allow separators: skip the separator and take the value after it
+      inc(i)
+      if prSepAllowDelimAfter in p.rules:
+        consumeDelims()
+    # prohibit separators: treat separator + remainder as the value
+    # this represents an error state but produces output that can be validated
     p.val = substr(cmd, i)
-    p.pos = 0
-    inc p.idx
-  else:
-    p.pos = i
+    p.advance(1)
+    return
+  elif canTakeVal and prShortValAllowAdjacent in p.rules and i < cmd.len:
+    # adjacent value
+    if prSepAllowDelimBefore in p.rules:
+      consumeDelims()
+    p.val = substr(cmd, i)
+    p.advance(1)
+    return
+  elif canTakeVal and
+      prShortValAllowNextArg in p.rules and
+      i >= cmd.len and
+      p.idx + 1 < p.cmds.len and (
+        prShortValAllowDashLeading in p.rules or
+        not (next().len > 0 and next()[0] == '-')):
+    # next-argument value
+    p.val = next()
+    p.advance(2)
+    return
+  p.pos = i
   if i >= cmd.len:
-    p.inShortState = false
-    p.pos = 0
-    inc p.idx
+    p.advance(1)
 
 proc next*(p: var OptParser) {.rtl, extern: "npo$1".} =
   ## Parses the next token.
@@ -343,54 +643,71 @@ proc next*(p: var OptParser) {.rtl, extern: "npo$1".} =
     return
 
   var i = p.pos
-  while i < p.cmds[p.idx].len and p.cmds[p.idx][i] in {'\t', ' '}: inc(i)
+  template cmd(): untyped = p.cmds[p.idx]
+  template nextArg(): untyped = p.cmds[p.idx + 1]
+
+  proc consumeDelims(cmds: openArray[string]; idx: int) =
+    while i < cmds[idx].len and cmds[idx][i] in DelimSet: inc(i)
+
+  proc advance(p: var OptParser; n = 1) =
+    p.pos = 0
+    inc p.idx, n
+
+  consumeDelims(p.cmds, p.idx)
   p.pos = i
   setLen(p.key, 0)
   setLen(p.val, 0)
   if p.inShortState:
     p.inShortState = false
-    if i >= p.cmds[p.idx].len:
-      inc(p.idx)
-      p.pos = 0
+    if i < cmd.len:
+      handleShortOption(p, p.cmds[p.idx])
+      return
+    else:
+      p.advance(1)
       if p.idx >= p.cmds.len:
         p.kind = cmdEnd
         return
-    else:
-      handleShortOption(p, p.cmds[p.idx])
-      return
 
-  if i < p.cmds[p.idx].len and p.cmds[p.idx][i] == '-':
+  if i < cmd.len and cmd[i] == '-':
     inc(i)
-    if i < p.cmds[p.idx].len and p.cmds[p.idx][i] == '-':
+    if i < cmd.len and cmd[i] == '-':
       p.kind = cmdLongOption
       inc(i)
-      i = parseWord(p.cmds[p.idx], i, p.key, {' ', '\t', ':', '='})
-      while i < p.cmds[p.idx].len and p.cmds[p.idx][i] in {'\t', ' '}: inc(i)
-      if i < p.cmds[p.idx].len and p.cmds[p.idx][i] in {':', '='}:
+      i = parseWord(cmd, i, p.key,
+        DelimSet + (if prLongAllowSep in p.rules: p.separators else: {}))
+      if prSepAllowDelimBefore in p.rules:
+        consumeDelims(p.cmds, p.idx)
+      if prLongAllowSep in p.rules and i < cmd.len and cmd[i] in p.separators:
         inc(i)
-        while i < p.cmds[p.idx].len and p.cmds[p.idx][i] in {'\t', ' '}: inc(i)
-        # if we're at the end, use the next command line option:
-        if i >= p.cmds[p.idx].len and p.idx < p.cmds.len and
-            p.allowWhitespaceAfterColon:
-          inc p.idx
-          i = 0
-        if p.idx < p.cmds.len:
-          p.val = p.cmds[p.idx].substr(i)
-      elif len(p.longNoVal) > 0 and p.key notin p.longNoVal and p.idx+1 < p.cmds.len:
-        p.val = p.cmds[p.idx+1]
-        inc p.idx
+        if prSepAllowDelimAfter in p.rules:
+          consumeDelims(p.cmds, p.idx)
+        if i >= cmd.len and p.idx + 1 < p.cmds.len and
+            prSepAllowDelimAfter in p.rules:
+          p.val = nextArg()
+          p.advance(2)
+        else:
+          p.val = cmd.substr(i)
+          p.advance(1)
+      elif prLongValAllowNextArg in p.rules and
+          len(p.longNoVal) > 0 and
+          p.key notin p.longNoVal and
+          p.idx + 1 < p.cmds.len:
+        p.val = nextArg()
+        p.advance(2)
       else:
-        p.val = ""
-      inc p.idx
-      p.pos = 0
+        if i < cmd.len:
+          # Leave remainder of the current token to be parsed as an argument.
+          consumeDelims(p.cmds, p.idx)
+          p.cmds[p.idx] = cmd.substr(i)
+        else:
+          p.advance(1)
     else:
       p.pos = i
-      handleShortOption(p, p.cmds[p.idx])
+      handleShortOption(p, cmd)
   else:
     p.kind = cmdArgument
-    p.key = p.cmds[p.idx]
-    inc p.idx
-    p.pos = 0
+    p.key = cmd
+    p.advance(1)
 
 when declared(quoteShellCommand):
   proc cmdLineRest*(p: OptParser): string {.rtl, extern: "npo$1".} =
@@ -399,15 +716,13 @@ when declared(quoteShellCommand):
     ## See also:
     ## * `remainingArgs proc<#remainingArgs,OptParser>`_
     ##
-    ## **Examples:**
-    ##   ```Nim
-    ##   var p = initOptParser("--left -r:2 -- foo.txt bar.txt")
-    ##   while true:
-    ##     p.next()
-    ##     if p.kind == cmdLongOption and p.key == "":  # Look for "--"
-    ##       break
-    ##   doAssert p.cmdLineRest == "foo.txt bar.txt"
-    ##   ```
+    runnableExamples:
+      var p = initOptParser("--left -r:2 -- foo.txt bar.txt")
+      while true:
+        p.next()
+        if p.kind == cmdLongOption and p.key == "":  # Look for "--"
+          break
+      doAssert p.cmdLineRest == "foo.txt bar.txt"
     result = p.cmds[p.idx .. ^1].quoteShellCommand
 
 proc remainingArgs*(p: OptParser): seq[string] {.rtl, extern: "npo$1".} =
@@ -416,15 +731,13 @@ proc remainingArgs*(p: OptParser): seq[string] {.rtl, extern: "npo$1".} =
   ## See also:
   ## * `cmdLineRest proc<#cmdLineRest,OptParser>`_
   ##
-  ## **Examples:**
-  ##   ```Nim
-  ##   var p = initOptParser("--left -r:2 -- foo.txt bar.txt")
-  ##   while true:
-  ##     p.next()
-  ##     if p.kind == cmdLongOption and p.key == "":  # Look for "--"
-  ##       break
-  ##   doAssert p.remainingArgs == @["foo.txt", "bar.txt"]
-  ##   ```
+  runnableExamples:
+    var p = initOptParser("--left -r:2 -- foo.txt bar.txt")
+    while true:
+      p.next()
+      if p.kind == cmdLongOption and p.key == "":  # Look for "--"
+        break
+    doAssert p.remainingArgs == @["foo.txt", "bar.txt"]
   result = @[]
   for i in p.idx..<p.cmds.len: result.add p.cmds[i]
 
@@ -439,29 +752,26 @@ iterator getopt*(p: var OptParser): tuple[kind: CmdLineKind, key,
   ## See also:
   ## * `initOptParser proc<#initOptParser,string,set[char],seq[string]>`_
   ##
-  ## **Examples:**
-  ##
-  ##   ```Nim
-  ##   # these are placeholders, of course
-  ##   proc writeHelp() = discard
-  ##   proc writeVersion() = discard
-  ##
-  ##   var filename: string
-  ##   var p = initOptParser("--left --debug:3 -l -r:2")
-  ##
-  ##   for kind, key, val in p.getopt():
-  ##     case kind
-  ##     of cmdArgument:
-  ##       filename = key
-  ##     of cmdLongOption, cmdShortOption:
-  ##       case key
-  ##       of "help", "h": writeHelp()
-  ##       of "version", "v": writeVersion()
-  ##     of cmdEnd: assert(false) # cannot happen
-  ##   if filename == "":
-  ##     # no filename has been given, so we show the help
-  ##     writeHelp()
-  ##   ```
+  runnableExamples:
+    # these are placeholders, of course
+    proc writeHelp() = discard
+    proc writeVersion() = discard
+
+    var filename: string = ""
+    var p = initOptParser("--left --debug:3 -l -r:2")
+
+    for kind, key, val in p.getopt():
+      case kind
+      of cmdArgument:
+        filename = key
+      of cmdLongOption, cmdShortOption:
+        case key
+        of "help", "h": writeHelp()
+        of "version", "v": writeVersion()
+      of cmdEnd: assert(false) # cannot happen
+    if filename == "":
+      # no filename has been given, so we show the help
+      writeHelp()
   p.pos = 0
   p.idx = 0
   while true:
@@ -469,8 +779,10 @@ iterator getopt*(p: var OptParser): tuple[kind: CmdLineKind, key,
     if p.kind == cmdEnd: break
     yield (p.kind, p.key, p.val)
 
-iterator getopt*(cmdline: seq[string] = @[],
-                  shortNoVal: set[char] = {}, longNoVal: seq[string] = @[]):
+iterator getopt*(cmdline: seq[string] = @[];
+                  shortNoVal: set[char] = {};
+                  longNoVal: seq[string] = @[];
+                  mode: CliMode = NimMode):
             tuple[kind: CmdLineKind, key, val: string] =
   ## Convenience iterator for iterating over command line arguments.
   ##
@@ -483,6 +795,9 @@ iterator getopt*(cmdline: seq[string] = @[],
   ## parameters<#nimshortnoval-and-nimlongnoval>`_ for more information on
   ## how this affects parsing.
   ##
+  ## `mode` selects the parser behavior profile (`NimMode`, `LaxMode`,
+  ## or `GnuMode`). See `Parser Modes`_ for details.
+  ##
   ## There is no need to check for `cmdEnd` while iterating. If using `getopt`
   ## with case switching, checking for `cmdEnd` is required.
   ##
@@ -513,7 +828,8 @@ iterator getopt*(cmdline: seq[string] = @[],
   ##     writeHelp()
   ##   ```
   var p = initOptParser(cmdline, shortNoVal = shortNoVal,
-      longNoVal = longNoVal)
+      longNoVal = longNoVal,
+      rules = toRules(mode))
   while true:
     next(p)
     if p.kind == cmdEnd: break

lib/pure/random.nim

@@ -243,7 +243,7 @@ proc rand[T: uint | uint64](r: var Rand; max: T): T =
       else:
         inc iters
 
-proc rand*(r: var Rand; max: Natural): int {.benign.} =
+proc rand*(r: var Rand; max: Natural): int {.gcsafe.} =
   ## Returns a random integer in the range `0..max` using the given state.
   ##
   ## **See also:**
@@ -260,7 +260,7 @@ proc rand*(r: var Rand; max: Natural): int {.benign.} =
   cast[int](rand(r, uint64(max)))
     # xxx toUnsigned pending https://github.com/nim-lang/Nim/pull/18445
 
-proc rand*(max: int): int {.benign.} =
+proc rand*(max: int): int {.gcsafe.} =
   ## Returns a random integer in the range `0..max`.
   ##
   ## If `randomize <#randomize>`_ has not been called, the sequence of random
@@ -281,7 +281,7 @@ proc rand*(max: int): int {.benign.} =
 
   rand(state, max)
 
-proc rand*(r: var Rand; max: range[0.0 .. high(float)]): float {.benign.} =
+proc rand*(r: var Rand; max: range[0.0 .. high(float)]): float {.gcsafe.} =
   ## Returns a random floating point number in the range `0.0..max`
   ## using the given state.
   ##
@@ -308,7 +308,7 @@ proc rand*(r: var Rand; max: range[0.0 .. high(float)]): float {.benign.} =
     let u = (0x3FFu64 shl 52u64) or (x shr 12u64)
     result = (cast[float](u) - 1.0) * max
 
-proc rand*(max: float): float {.benign.} =
+proc rand*(max: float): float {.gcsafe.} =
   ## Returns a random floating point number in the range `0.0..max`.
   ##
   ## If `randomize <#randomize>`_ has not been called, the sequence of random
@@ -612,7 +612,7 @@ proc initRand*(seed: int64): Rand =
     skipRandomNumbers(result)
   discard next(result)
 
-proc randomize*(seed: int64) {.benign.} =
+proc randomize*(seed: int64) {.gcsafe.} =
   ## Initializes the default random number generator with the given seed.
   ##
   ## Providing a specific seed will produce the same results for that seed each time.
@@ -736,7 +736,7 @@ when not defined(standalone):
   since (1, 5, 1):
     export initRand
 
-  proc randomize*() {.benign.} =
+  proc randomize*() {.gcsafe.} =
     ## Initializes the default random number generator with a seed based on
     ## random number source.
     ##

lib/pure/streams.nim

@@ -16,9 +16,9 @@
 ## stream interface.
 ##
 ## .. warning:: Due to the use of `pointer`, the `readData`, `peekData` and
-## `writeData` interfaces are not available on the compile-time VM, and must
-## be cast from a `ptr string` on the JS backend. However, `readDataStr` is
-## available generally in place of `readData`.
+##   `writeData` interfaces are not available on the compile-time VM, and must
+##   be cast from a `ptr string` on the JS backend. However, `readDataStr` is
+##   available generally in place of `readData`.
 ##
 ## Basic usage
 ## ===========

lib/pure/times.nim

@@ -382,9 +382,9 @@ type
       ## timezones. The `times` module only supplies implementations for the
       ## system's local time and UTC.
     zonedTimeFromTimeImpl: proc (x: Time): ZonedTime
-        {.tags: [], raises: [], benign.}
+        {.tags: [], raises: [], gcsafe.}
     zonedTimeFromAdjTimeImpl: proc (x: Time): ZonedTime
-        {.tags: [], raises: [], benign.}
+        {.tags: [], raises: [], gcsafe.}
     name: string
 
   ZonedTime* = object ## Represents a point in time with an associated
@@ -432,7 +432,7 @@ else:
 # Helper procs
 #
 
-{.pragma: operator, rtl, noSideEffect, benign.}
+{.pragma: operator, rtl, noSideEffect, gcsafe.}
 
 proc convert*[T: SomeInteger](unitFrom, unitTo: FixedTimeUnit, quantity: T): T
     {.inline.} =
@@ -518,7 +518,7 @@ proc fromEpochDay(epochday: int64):
   return (d.MonthdayRange, m.Month, (y + ord(m <= 2)).int)
 
 proc getDayOfYear*(monthday: MonthdayRange, month: Month, year: int):
-    YeardayRange {.tags: [], raises: [], benign.} =
+    YeardayRange {.tags: [], raises: [], gcsafe.} =
   ## Returns the day of the year.
   ## Equivalent with `dateTime(year, month, monthday, 0, 0, 0, 0).yearday`.
   runnableExamples:
@@ -538,7 +538,7 @@ proc getDayOfYear*(monthday: MonthdayRange, month: Month, year: int):
     result = daysUntilMonth[month] + monthday - 1
 
 proc getDayOfWeek*(monthday: MonthdayRange, month: Month, year: int): WeekDay
-    {.tags: [], raises: [], benign.} =
+    {.tags: [], raises: [], gcsafe.} =
   ## Returns the day of the week enum from day, month and year.
   ## Equivalent with `dateTime(year, month, monthday, 0, 0, 0, 0).weekday`.
   runnableExamples:
@@ -922,21 +922,21 @@ proc nanosecond*(time: Time): NanosecondRange =
   time.nanosecond
 
 proc fromUnix*(unix: int64): Time
-    {.benign, tags: [], raises: [], noSideEffect.} =
+    {.gcsafe, tags: [], raises: [], noSideEffect.} =
   ## Convert a unix timestamp (seconds since `1970-01-01T00:00:00Z`)
   ## to a `Time`.
   runnableExamples:
     doAssert $fromUnix(0).utc == "1970-01-01T00:00:00Z"
   initTime(unix, 0)
 
-proc toUnix*(t: Time): int64 {.benign, tags: [], raises: [], noSideEffect.} =
+proc toUnix*(t: Time): int64 {.gcsafe, tags: [], raises: [], noSideEffect.} =
   ## Convert `t` to a unix timestamp (seconds since `1970-01-01T00:00:00Z`).
   ## See also `toUnixFloat` for subsecond resolution.
   runnableExamples:
     doAssert fromUnix(0).toUnix() == 0
   t.seconds
 
-proc fromUnixFloat(seconds: float): Time {.benign, tags: [], raises: [], noSideEffect.} =
+proc fromUnixFloat(seconds: float): Time {.gcsafe, tags: [], raises: [], noSideEffect.} =
   ## Convert a unix timestamp in seconds to a `Time`; same as `fromUnix`
   ## but with subsecond resolution.
   runnableExamples:
@@ -946,7 +946,7 @@ proc fromUnixFloat(seconds: float): Time {.benign, tags: [], raises: [], noSideE
   let nsecs = (seconds - secs) * 1e9
   initTime(secs.int64, nsecs.NanosecondRange)
 
-proc toUnixFloat(t: Time): float {.benign, tags: [], raises: [].} =
+proc toUnixFloat(t: Time): float {.gcsafe, tags: [], raises: [].} =
   ## Same as `toUnix` but using subsecond resolution.
   runnableExamples:
     let t = getTime()
@@ -975,7 +975,7 @@ proc toWinTime*(t: Time): int64 =
 proc getTimeImpl(typ: typedesc[Time]): Time =
   raiseAssert "implemented in the vm"
 
-proc getTime*(): Time {.tags: [TimeEffect], benign.} =
+proc getTime*(): Time {.tags: [TimeEffect], gcsafe.} =
   ## Gets the current time as a `Time` with up to nanosecond resolution.
   when nimvm:
     result = getTimeImpl(Time)
@@ -1154,7 +1154,7 @@ proc isLeapDay*(dt: DateTime): bool {.since: (1, 1).} =
   assertDateTimeInitialized dt
   dt.year.isLeapYear and dt.month == mFeb and dt.monthday == 29
 
-proc toTime*(dt: DateTime): Time {.tags: [], raises: [], benign.} =
+proc toTime*(dt: DateTime): Time {.tags: [], raises: [], gcsafe.} =
   ## Converts a `DateTime` to a `Time` representing the same point in time.
   assertDateTimeInitialized dt
   let epochDay = toEpochDay(dt.monthday, dt.month, dt.year)
@@ -1197,9 +1197,9 @@ proc initDateTime(zt: ZonedTime, zone: Timezone): DateTime =
 proc newTimezone*(
       name: string,
       zonedTimeFromTimeImpl: proc (time: Time): ZonedTime
-          {.tags: [], raises: [], benign.},
+          {.tags: [], raises: [], gcsafe.},
       zonedTimeFromAdjTimeImpl: proc (adjTime: Time): ZonedTime
-          {.tags: [], raises: [], benign.}
+          {.tags: [], raises: [], gcsafe.}
     ): owned Timezone =
   ## Create a new `Timezone`.
   ##
@@ -1263,12 +1263,12 @@ proc `==`*(zone1, zone2: Timezone): bool =
   zone1.name == zone2.name
 
 proc inZone*(time: Time, zone: Timezone): DateTime
-    {.tags: [], raises: [], benign.} =
+    {.tags: [], raises: [], gcsafe.} =
   ## Convert `time` into a `DateTime` using `zone` as the timezone.
   result = initDateTime(zone.zonedTimeFromTime(time), zone)
 
 proc inZone*(dt: DateTime, zone: Timezone): DateTime
-    {.tags: [], raises: [], benign.} =
+    {.tags: [], raises: [], gcsafe.} =
   ## Returns a `DateTime` representing the same point in time as `dt` but
   ## using `zone` as the timezone.
   assertDateTimeInitialized dt
@@ -1283,14 +1283,14 @@ proc toAdjTime(dt: DateTime): Time =
   result = initTime(seconds, dt.nanosecond)
 
 when defined(js):
-  proc localZonedTimeFromTime(time: Time): ZonedTime {.benign.} =
+  proc localZonedTimeFromTime(time: Time): ZonedTime {.gcsafe.} =
     let jsDate = newDate(time.seconds * 1000)
     let offset = jsDate.getTimezoneOffset() * secondsInMin
     result.time = time
     result.utcOffset = offset
     result.isDst = false
 
-  proc localZonedTimeFromAdjTime(adjTime: Time): ZonedTime {.benign.} =
+  proc localZonedTimeFromAdjTime(adjTime: Time): ZonedTime {.gcsafe.} =
     let utcDate = newDate(adjTime.seconds * 1000)
     let localDate = newDate(utcDate.getUTCFullYear(), utcDate.getUTCMonth(),
         utcDate.getUTCDate(), utcDate.getUTCHours(), utcDate.getUTCMinutes(),
@@ -1337,11 +1337,11 @@ else:
       return ((a.int64 - tm.toAdjUnix).int, tm.tm_isdst > 0)
     return (0, false)
 
-  proc localZonedTimeFromTime(time: Time): ZonedTime {.benign.} =
+  proc localZonedTimeFromTime(time: Time): ZonedTime {.gcsafe.} =
     let (offset, dst) = getLocalOffsetAndDst(time.seconds)
     result = ZonedTime(time: time, utcOffset: offset, isDst: dst)
 
-  proc localZonedTimeFromAdjTime(adjTime: Time): ZonedTime {.benign.} =
+  proc localZonedTimeFromAdjTime(adjTime: Time): ZonedTime {.gcsafe.} =
     var adjUnix = adjTime.seconds
     let past = adjUnix - secondsInDay
     let (pastOffset, _) = getLocalOffsetAndDst(past)
@@ -1408,7 +1408,7 @@ proc local*(t: Time): DateTime =
   ## Shorthand for `t.inZone(local())`.
   t.inZone(local())
 
-proc now*(): DateTime {.tags: [TimeEffect], benign.} =
+proc now*(): DateTime {.tags: [TimeEffect], gcsafe.} =
   ## Get the current time as a  `DateTime` in the local timezone.
   ## Shorthand for `getTime().local`.
   ##
@@ -2327,7 +2327,7 @@ proc parseTime*(input: string, f: static[string], zone: Timezone): Time
   const f2 = initTimeFormat(f)
   result = input.parse(f2, zone).toTime()
 
-proc `$`*(dt: DateTime): string {.tags: [], raises: [], benign.} =
+proc `$`*(dt: DateTime): string {.tags: [], raises: [], gcsafe.} =
   ## Converts a `DateTime` object to a string representation.
   ## It uses the format `yyyy-MM-dd'T'HH:mm:sszzz`.
   runnableExamples:
@@ -2339,7 +2339,7 @@ proc `$`*(dt: DateTime): string {.tags: [], raises: [], benign.} =
   else:
     result = format(dt, "yyyy-MM-dd'T'HH:mm:sszzz")
 
-proc `$`*(time: Time): string {.tags: [], raises: [], benign.} =
+proc `$`*(time: Time): string {.tags: [], raises: [], gcsafe.} =
   ## Converts a `Time` value to a string representation. It will use the local
   ## time zone and use the format `yyyy-MM-dd'T'HH:mm:sszzz`.
   runnableExamples:

lib/pure/typetraits.nim

@@ -96,6 +96,9 @@ proc supportsCopyMem*(t: typedesc): bool {.magic: "TypeTrait".}
   ##
   ## Other languages name a type like these `blob`:idx:.
 
+proc canFormCycles*(t: typedesc): bool {.magic: "TypeTrait".}
+  ## Returns true if `t` can form cycles.
+
 proc hasDefaultValue*(t: typedesc): bool {.magic: "TypeTrait".} =
   ## Returns true if `t` has a valid default value.
   runnableExamples:

lib/std/private/osdirs.nim

@@ -331,7 +331,7 @@ proc rawRemoveDir(dir: string) {.noWeirdTarget.} =
     if rmdir(dir) != 0'i32 and errno != ENOENT: raiseOSError(osLastError(), dir)
 
 proc removeDir*(dir: string, checkDir = false) {.rtl, extern: "nos$1", tags: [
-  WriteDirEffect, ReadDirEffect], benign, noWeirdTarget.} =
+  WriteDirEffect, ReadDirEffect], gcsafe, noWeirdTarget.} =
   ## Removes the directory `dir` including all subdirectories and files
   ## in `dir` (recursively).
   ##
@@ -441,7 +441,7 @@ proc createDir*(dir: string) {.rtl, extern: "nos$1",
       discard existsOrCreateDir(p)
 
 proc copyDir*(source, dest: string, skipSpecial = false) {.rtl, extern: "nos$1",
-  tags: [ReadDirEffect, WriteIOEffect, ReadIOEffect], benign, noWeirdTarget.} =
+  tags: [ReadDirEffect, WriteIOEffect, ReadIOEffect], gcsafe, noWeirdTarget.} =
   ## Copies a directory from `source` to `dest`.
   ##
   ## On non-Windows OSes, symlinks are copied as symlinks. On Windows, symlinks
@@ -482,7 +482,7 @@ proc copyDirWithPermissions*(source, dest: string,
                              ignorePermissionErrors = true,
                              skipSpecial = false)
   {.rtl, extern: "nos$1", tags: [ReadDirEffect, WriteIOEffect, ReadIOEffect],
-   benign, noWeirdTarget.} =
+   gcsafe, noWeirdTarget.} =
   ## Copies a directory from `source` to `dest` preserving file permissions.
   ##
   ## On non-Windows OSes, symlinks are copied as symlinks. On Windows, symlinks

lib/std/syncio.nim

@@ -182,7 +182,7 @@ proc checkErr(f: File) =
 
 {.push stackTrace: off, profiler: off.}
 proc readBuffer*(f: File, buffer: pointer, len: Natural): int {.
-  tags: [ReadIOEffect], benign.} =
+  tags: [ReadIOEffect], gcsafe.} =
   ## Reads `len` bytes into the buffer pointed to by `buffer`. Returns
   ## the actual number of bytes that have been read which may be less than
   ## `len` (if not as many bytes are remaining), but not greater.
@@ -191,20 +191,20 @@ proc readBuffer*(f: File, buffer: pointer, len: Natural): int {.
 
 proc readBytes*(f: File, a: var openArray[int8|uint8], start,
     len: Natural): int {.
-  tags: [ReadIOEffect], benign.} =
+  tags: [ReadIOEffect], gcsafe.} =
   ## Reads `len` bytes into the buffer `a` starting at `a[start]`. Returns
   ## the actual number of bytes that have been read which may be less than
   ## `len` (if not as many bytes are remaining), but not greater.
   result = readBuffer(f, addr(a[start]), len)
 
-proc readChars*(f: File, a: var openArray[char]): int {.tags: [ReadIOEffect], benign.} =
+proc readChars*(f: File, a: var openArray[char]): int {.tags: [ReadIOEffect], gcsafe.} =
   ## Reads up to `a.len` bytes into the buffer `a`. Returns
   ## the actual number of bytes that have been read which may be less than
   ## `a.len` (if not as many bytes are remaining), but not greater.
   result = readBuffer(f, addr(a[0]), a.len)
 
 proc readChars*(f: File, a: var openArray[char], start, len: Natural): int {.
-  tags: [ReadIOEffect], benign, deprecated:
+  tags: [ReadIOEffect], gcsafe, deprecated:
     "use other `readChars` overload, possibly via: readChars(toOpenArray(buf, start, len-1))".} =
   ## Reads `len` bytes into the buffer `a` starting at `a[start]`. Returns
   ## the actual number of bytes that have been read which may be less than
@@ -213,13 +213,13 @@ proc readChars*(f: File, a: var openArray[char], start, len: Natural): int {.
     raiseEIO("buffer overflow: (start+len) > length of openarray buffer")
   result = readBuffer(f, addr(a[start]), len)
 
-proc write*(f: File, c: cstring) {.tags: [WriteIOEffect], benign.} =
+proc write*(f: File, c: cstring) {.tags: [WriteIOEffect], gcsafe.} =
   ## Writes a value to the file `f`. May throw an IO exception.
   discard c_fputs(c, f)
   checkErr(f)
 
 proc writeBuffer*(f: File, buffer: pointer, len: Natural): int {.
-  tags: [WriteIOEffect], benign.} =
+  tags: [WriteIOEffect], gcsafe.} =
   ## Writes the bytes of buffer pointed to by the parameter `buffer` to the
   ## file `f`. Returns the number of actual written bytes, which may be less
   ## than `len` in case of an error.
@@ -227,7 +227,7 @@ proc writeBuffer*(f: File, buffer: pointer, len: Natural): int {.
   checkErr(f)
 
 proc writeBytes*(f: File, a: openArray[int8|uint8], start, len: Natural): int {.
-  tags: [WriteIOEffect], benign.} =
+  tags: [WriteIOEffect], gcsafe.} =
   ## Writes the bytes of `a[start..start+len-1]` to the file `f`. Returns
   ## the number of actual written bytes, which may be less than `len` in case
   ## of an error.
@@ -235,7 +235,7 @@ proc writeBytes*(f: File, a: openArray[int8|uint8], start, len: Natural): int {.
   result = writeBuffer(f, addr(x[int(start)]), len)
 
 proc writeChars*(f: File, a: openArray[char], start, len: Natural): int {.
-  tags: [WriteIOEffect], benign.} =
+  tags: [WriteIOEffect], gcsafe.} =
   ## Writes the bytes of `a[start..start+len-1]` to the file `f`. Returns
   ## the number of actual written bytes, which may be less than `len` in case
   ## of an error.
@@ -264,7 +264,7 @@ when defined(windows):
           break
         inc i, w
 
-proc write*(f: File, s: string) {.tags: [WriteIOEffect], benign.} =
+proc write*(f: File, s: string) {.tags: [WriteIOEffect], gcsafe.} =
   when defined(windows):
     writeWindows(f, s, doRaise = true)
   else:
@@ -393,7 +393,7 @@ when defined(nimdoc) or (defined(posix) and not defined(nimscript)) or defined(w
                                     inheritable.WinDWORD) != 0
 
 proc readLine*(f: File, line: var string): bool {.tags: [ReadIOEffect],
-              benign.} =
+              gcsafe.} =
   ## Reads a line of text from the file `f` into `line`. May throw an IO
   ## exception.
   ## A line of text may be delimited by `LF` or `CRLF`. The newline
@@ -519,43 +519,43 @@ proc readLine*(f: File, line: var string): bool {.tags: [ReadIOEffect],
     sp = 128 # read in 128 bytes at a time
     line.setLen(pos+sp)
 
-proc readLine*(f: File): string {.tags: [ReadIOEffect], benign.} =
+proc readLine*(f: File): string {.tags: [ReadIOEffect], gcsafe.} =
   ## Reads a line of text from the file `f`. May throw an IO exception.
   ## A line of text may be delimited by `LF` or `CRLF`. The newline
   ## character(s) are not part of the returned string.
   result = newStringOfCap(80)
   if not readLine(f, result): raiseEOF()
 
-proc write*(f: File, i: int) {.tags: [WriteIOEffect], benign.} =
+proc write*(f: File, i: int) {.tags: [WriteIOEffect], gcsafe.} =
   when sizeof(int) == 8:
     if c_fprintf(f, "%lld", i) < 0: checkErr(f)
   else:
     if c_fprintf(f, "%ld", i) < 0: checkErr(f)
 
-proc write*(f: File, i: BiggestInt) {.tags: [WriteIOEffect], benign.} =
+proc write*(f: File, i: BiggestInt) {.tags: [WriteIOEffect], gcsafe.} =
   when sizeof(BiggestInt) == 8:
     if c_fprintf(f, "%lld", i) < 0: checkErr(f)
   else:
     if c_fprintf(f, "%ld", i) < 0: checkErr(f)
 
-proc write*(f: File, b: bool) {.tags: [WriteIOEffect], benign.} =
+proc write*(f: File, b: bool) {.tags: [WriteIOEffect], gcsafe.} =
   if b: write(f, "true")
   else: write(f, "false")
 
-proc write*(f: File, r: float32) {.tags: [WriteIOEffect], benign.} =
+proc write*(f: File, r: float32) {.tags: [WriteIOEffect], gcsafe.} =
   var buffer {.noinit.}: array[65, char]
   discard writeFloatToBuffer(buffer, r)
   if c_fprintf(f, "%s", buffer[0].addr) < 0: checkErr(f)
 
-proc write*(f: File, r: BiggestFloat) {.tags: [WriteIOEffect], benign.} =
+proc write*(f: File, r: BiggestFloat) {.tags: [WriteIOEffect], gcsafe.} =
   var buffer {.noinit.}: array[65, char]
   discard writeFloatToBuffer(buffer, r)
   if c_fprintf(f, "%s", buffer[0].addr) < 0: checkErr(f)
 
-proc write*(f: File, c: char) {.tags: [WriteIOEffect], benign.} =
+proc write*(f: File, c: char) {.tags: [WriteIOEffect], gcsafe.} =
   discard c_putc(cint(c), f)
 
-proc write*(f: File, a: varargs[string, `$`]) {.tags: [WriteIOEffect], benign.} =
+proc write*(f: File, a: varargs[string, `$`]) {.tags: [WriteIOEffect], gcsafe.} =
   for x in items(a): write(f, x)
 
 proc readAllBuffer(file: File): string =
@@ -579,7 +579,7 @@ proc rawFileSize(file: File): int64 =
   result = c_ftell(file)
   discard c_fseek(file, oldPos, 0)
 
-proc endOfFile*(f: File): bool {.tags: [], benign.} =
+proc endOfFile*(f: File): bool {.tags: [], gcsafe.} =
   ## Returns true if `f` is at the end.
   var c = c_fgetc(f)
   discard c_ungetc(c, f)
@@ -603,7 +603,7 @@ proc readAllFile(file: File): string =
   var len = rawFileSize(file)
   result = readAllFile(file, len)
 
-proc readAll*(file: File): string {.tags: [ReadIOEffect], benign.} =
+proc readAll*(file: File): string {.tags: [ReadIOEffect], gcsafe.} =
   ## Reads all data from the stream `file`.
   ##
   ## Raises an IO exception in case of an error. It is an error if the
@@ -621,7 +621,7 @@ proc readAll*(file: File): string {.tags: [ReadIOEffect], benign.} =
     result = readAllBuffer(file)
 
 proc writeLine*[Ty](f: File, x: varargs[Ty, `$`]) {.inline,
-                          tags: [WriteIOEffect], benign.} =
+                          tags: [WriteIOEffect], gcsafe.} =
   ## Writes the values `x` to `f` and then writes "\\n".
   ## May throw an IO exception.
   for i in items(x):
@@ -713,7 +713,7 @@ when defined(posix) and not defined(nimscript):
 
 proc open*(f: var File, filename: string,
           mode: FileMode = fmRead,
-          bufSize: int = -1): bool {.tags: [], raises: [], benign.} =
+          bufSize: int = -1): bool {.tags: [], raises: [], gcsafe.} =
   ## Opens a file named `filename` with given `mode`.
   ##
   ## Default mode is readonly. Returns true if the file could be opened.
@@ -747,7 +747,7 @@ proc open*(f: var File, filename: string,
     result = false
 
 proc reopen*(f: File, filename: string, mode: FileMode = fmRead): bool {.
-  tags: [], benign.} =
+  tags: [], gcsafe.} =
   ## Reopens the file `f` with given `filename` and `mode`. This
   ## is often used to redirect the `stdin`, `stdout` or `stderr`
   ## file variables.
@@ -766,7 +766,7 @@ proc reopen*(f: File, filename: string, mode: FileMode = fmRead): bool {.
     result = false
 
 proc open*(f: var File, filehandle: FileHandle,
-           mode: FileMode = fmRead): bool {.tags: [], raises: [], benign.} =
+           mode: FileMode = fmRead): bool {.tags: [], raises: [], gcsafe.} =
   ## Creates a `File` from a `filehandle` with given `mode`.
   ##
   ## Default mode is readonly. Returns true if the file could be opened.
@@ -792,26 +792,26 @@ proc open*(filename: string,
   if not open(result, filename, mode, bufSize):
     raise newException(IOError, "cannot open: " & filename)
 
-proc setFilePos*(f: File, pos: int64, relativeTo: FileSeekPos = fspSet) {.benign, sideEffect.} =
+proc setFilePos*(f: File, pos: int64, relativeTo: FileSeekPos = fspSet) {.gcsafe, sideEffect.} =
   ## Sets the position of the file pointer that is used for read/write
   ## operations. The file's first byte has the index zero.
   if c_fseek(f, pos, cint(relativeTo)) != 0:
     raiseEIO("cannot set file position")
 
-proc getFilePos*(f: File): int64 {.benign.} =
+proc getFilePos*(f: File): int64 {.gcsafe.} =
   ## Retrieves the current position of the file pointer that is used to
   ## read from the file `f`. The file's first byte has the index zero.
   result = c_ftell(f)
   if result < 0: raiseEIO("cannot retrieve file position")
 
-proc getFileSize*(f: File): int64 {.tags: [ReadIOEffect], benign.} =
+proc getFileSize*(f: File): int64 {.tags: [ReadIOEffect], gcsafe.} =
   ## Retrieves the file size (in bytes) of `f`.
   let oldPos = getFilePos(f)
   discard c_fseek(f, 0, 2) # seek the end of the file
   result = getFilePos(f)
   setFilePos(f, oldPos)
 
-proc setStdIoUnbuffered*() {.tags: [], benign.} =
+proc setStdIoUnbuffered*() {.tags: [], gcsafe.} =
   ## Configures `stdin`, `stdout` and `stderr` to be unbuffered.
   when declared(stdout):
     discard c_setvbuf(stdout, nil, IONBF, 0)
@@ -865,7 +865,7 @@ when defined(windows) and appType == "console" and
     discard setConsoleCP(Utf8codepage)
     addExitProc(restoreConsoleCP)
 
-proc readFile*(filename: string): string {.tags: [ReadIOEffect], benign.} =
+proc readFile*(filename: string): string {.tags: [ReadIOEffect], gcsafe.} =
   ## Opens a file named `filename` for reading, calls `readAll
   ## <#readAll,File>`_ and closes the file afterwards. Returns the string.
   ## Raises an IO exception in case of an error. If you need to call
@@ -880,7 +880,7 @@ proc readFile*(filename: string): string {.tags: [ReadIOEffect], benign.} =
   else:
     raise newException(IOError, "cannot open: " & filename)
 
-proc writeFile*(filename, content: string) {.tags: [WriteIOEffect], benign.} =
+proc writeFile*(filename, content: string) {.tags: [WriteIOEffect], gcsafe.} =
   ## Opens a file named `filename` for writing. Then writes the
   ## `content` completely to the file and closes the file afterwards.
   ## Raises an IO exception in case of an error.

lib/std/sysatomics.nim

@@ -219,16 +219,16 @@ elif someVcc:
     elif mem == ATOMIC_ACQ_REL: fence()
     elif mem == ATOMIC_SEQ_CST: fence()
 
-  proc atomicStoreN*[T: AtomType](p: ptr T, val: T, mem: static[AtomMemModel]) =
+  proc atomicStoreN*[T: AtomType](p: ptr T, val: T, mem: static[AtomMemModel]) {.enforcenoraises.} =
     barrier(mem)
     p[] = val
 
-  proc atomicLoadN*[T: AtomType](p: ptr T, mem: static[AtomMemModel]): T =
+  proc atomicLoadN*[T: AtomType](p: ptr T, mem: static[AtomMemModel]): T {.enforcenoraises.} =
     result = p[]
     barrier(mem)
 
   proc atomicCompareExchangeN*[T: ptr](p, expected: ptr T, desired: T,
-    weak: bool, success_memmodel: AtomMemModel, failure_memmodel: AtomMemModel): bool =
+    weak: bool, success_memmodel: AtomMemModel, failure_memmodel: AtomMemModel): bool {.enforcenoraises.} =
     when sizeof(T) == 8:
       interlockedCompareExchange64(p, cast[int64](desired), cast[int64](expected[])) ==
         cast[int64](expected[])
@@ -236,7 +236,7 @@ elif someVcc:
       interlockedCompareExchange32(p, cast[int32](desired), cast[int32](expected[])) ==
         cast[int32](expected[])
 
-  proc atomicExchangeN*[T: ptr](p: ptr T, val: T, mem: AtomMemModel): T =
+  proc atomicExchangeN*[T: ptr](p: ptr T, val: T, mem: AtomMemModel): T {.enforcenoraises.} =
     when sizeof(T) == 8:
       cast[T](interlockedExchange64(p, cast[int64](val)))
     elif sizeof(T) == 4:

lib/system.nim

@@ -627,7 +627,7 @@ proc newSeq*[T](s: var seq[T], len: Natural) {.magic: "NewSeq", noSideEffect.}
   ##   #inputStrings[3] = "out of bounds"
   ##   ```
 
-proc newSeq*[T](len = 0.Natural): seq[T] =
+proc newSeq*[T](len = 0.Natural): seq[T] {.noSideEffect.} =
   ## Creates a new sequence of type `seq[T]` with length `len`.
   ##
   ## Note that the sequence will be filled with zeroed entries.
@@ -1147,7 +1147,7 @@ template sysAssert(cond: bool, msg: string) =
 const hasAlloc = (hostOS != "standalone" or not defined(nogc)) and not defined(nimscript)
 
 when notJSnotNims and hasAlloc and not defined(nimSeqsV2):
-  proc addChar(s: NimString, c: char): NimString {.compilerproc, benign.}
+  proc addChar(s: NimString, c: char): NimString {.compilerproc, gcsafe.}
 
 when defined(nimscript) or not defined(nimSeqsV2):
   proc add*[T](x: var seq[T], y: sink T) {.magic: "AppendSeqElem", noSideEffect.}
@@ -1459,6 +1459,7 @@ proc isNil*[T: proc | iterator {.closure.}](x: T): bool {.noSideEffect, magic: "
   ## `== nil`.
 
 proc supportsCopyMem(t: typedesc): bool {.magic: "TypeTrait".}
+proc canFormCycles(t: typedesc): bool {.magic: "TypeTrait".}
 
 when defined(nimHasTopDownInference):
   # magic used for seq type inference
@@ -1664,7 +1665,7 @@ when not defined(js) and hasThreadSupport and hostOS != "standalone":
 
 when not defined(js) and defined(nimV2):
   type
-    DestructorProc = proc (p: pointer) {.nimcall, benign, raises: [].}
+    DestructorProc = proc (p: pointer) {.nimcall, gcsafe, raises: [].}
     TNimTypeV2 {.compilerproc.} = object
       destructor: pointer
       size: int
@@ -1776,7 +1777,7 @@ when not defined(nimscript):
 when not declared(sysFatal):
   include "system/fatal"
 
-proc echo*(x: varargs[typed, `$`]) {.magic: "Echo", benign, sideEffect.}
+proc echo*(x: varargs[typed, `$`]) {.magic: "Echo", gcsafe, sideEffect.}
   ## Writes and flushes the parameters to the standard output.
   ##
   ## Special built-in that takes a variable number of arguments. Each argument
@@ -1883,7 +1884,7 @@ when notJSnotNims:
       ## lead to the `raise` statement. This only works for debug builds.
 
   var
-    globalRaiseHook*: proc (e: ref Exception): bool {.nimcall, benign.}
+    globalRaiseHook*: proc (e: ref Exception): bool {.nimcall, gcsafe.}
       ## With this hook you can influence exception handling on a global level.
       ## If not nil, every 'raise' statement ends up calling this hook.
       ##
@@ -1892,7 +1893,7 @@ when notJSnotNims:
       ## If `globalRaiseHook` returns false, the exception is caught and does
       ## not propagate further through the call stack.
 
-    localRaiseHook* {.threadvar.}: proc (e: ref Exception): bool {.nimcall, benign.}
+    localRaiseHook* {.threadvar.}: proc (e: ref Exception): bool {.nimcall, gcsafe.}
       ## With this hook you can influence exception handling on a
       ## thread local level.
       ## If not nil, every 'raise' statement ends up calling this hook.
@@ -1902,7 +1903,7 @@ when notJSnotNims:
       ## If `localRaiseHook` returns false, the exception
       ## is caught and does not propagate further through the call stack.
 
-    outOfMemHook*: proc () {.nimcall, tags: [], benign, raises: [].}
+    outOfMemHook*: proc () {.nimcall, tags: [], gcsafe, raises: [].}
       ## Set this variable to provide a procedure that should be called
       ## in case of an `out of memory`:idx: event. The standard handler
       ## writes an error message and terminates the program.
@@ -1923,7 +1924,7 @@ when notJSnotNims:
       ## If the handler does not raise an exception, ordinary control flow
       ## continues and the program is terminated.
 
-    unhandledExceptionHook*: proc (e: ref Exception) {.nimcall, tags: [], benign, raises: [].}
+    unhandledExceptionHook*: proc (e: ref Exception) {.nimcall, tags: [], gcsafe, raises: [].}
       ## Set this variable to provide a procedure that should be called
       ## in case of an `unhandle exception` event. The standard handler
       ## writes an error message and terminates the program, except when
@@ -2066,7 +2067,7 @@ when hostOS == "standalone" and defined(nogc):
     if s == nil or s.len == 0: result = cstring""
     else: result = cast[cstring](addr s.data)
 
-proc getTypeInfo*[T](x: T): pointer {.magic: "GetTypeInfo", benign.}
+proc getTypeInfo*[T](x: T): pointer {.magic: "GetTypeInfo", gcsafe.}
   ## Get type information for `x`.
   ##
   ## Ordinary code should not use this, but the `typeinfo module
@@ -2285,21 +2286,21 @@ when not defined(js) and declared(alloc0) and declared(dealloc):
     dealloc(a)
 
 when notJSnotNims and hostOS != "standalone":
-  proc getCurrentException*(): ref Exception {.compilerRtl, inl, benign.} =
+  proc getCurrentException*(): ref Exception {.compilerRtl, inl, gcsafe.} =
     ## Retrieves the current exception; if there is none, `nil` is returned.
     result = currException
 
-  proc nimBorrowCurrentException(): ref Exception {.compilerRtl, inl, benign, nodestroy.} =
+  proc nimBorrowCurrentException(): ref Exception {.compilerRtl, inl, gcsafe, nodestroy.} =
     # .nodestroy here so that we do not produce a write barrier as the
     # C codegen only uses it in a borrowed way:
     result = currException
 
-  proc getCurrentExceptionMsg*(): string {.inline, benign.} =
+  proc getCurrentExceptionMsg*(): string {.inline, gcsafe.} =
     ## Retrieves the error message that was attached to the current
     ## exception; if there is none, `""` is returned.
     return if currException == nil: "" else: currException.msg
 
-  proc setCurrentException*(exc: ref Exception) {.inline, benign.} =
+  proc setCurrentException*(exc: ref Exception) {.inline, gcsafe.} =
     ## Sets the current exception.
     ##
     ## .. warning:: Only use this if you know what you are doing.

lib/system/alloc.nim

@@ -104,6 +104,8 @@ type
       zeroField: int       # 0 means cell is not used (overlaid with typ field)
                           # 1 means cell is manually managed pointer
                           # otherwise a PNimType is stored in there
+      when sizeof(int) == 4:  # 32-bit only
+        headerAlignPad: array[8, byte]  # so addr(data) ≡ 8 (mod 16)
     else:
       alignment: int
 
@@ -725,7 +727,7 @@ proc getSmallChunk(a: var MemRegion): PSmallChunk =
 
 # -----------------------------------------------------------------------------
 when not defined(gcDestructors):
-  proc isAllocatedPtr(a: MemRegion, p: pointer): bool {.benign.}
+  proc isAllocatedPtr(a: MemRegion, p: pointer): bool {.gcsafe.}
 
 when true:
   template allocInv(a: MemRegion): bool = true
@@ -851,12 +853,12 @@ when defined(heaptrack):
 
 proc bigChunkAlignOffset(alignment: int): int {.inline.} =
   ## Compute the alignment offset for big chunk data.
-  if alignment <= MemAlign:
+  if alignment == 0:
     result = 0
   else:
-    result = align(sizeof(BigChunk) + sizeof(Cell), alignment) - sizeof(BigChunk) - sizeof(Cell)
+    result = align(sizeof(BigChunk) + sizeof(FreeCell), alignment) - sizeof(BigChunk) - sizeof(FreeCell)
 
-proc rawAlloc(a: var MemRegion, requestedSize: int, alignment: int = MemAlign): pointer =
+proc rawAlloc(a: var MemRegion, requestedSize: int, alignment: int = 0): pointer =
   when defined(nimTypeNames):
     inc(a.allocCounter)
   sysAssert(allocInv(a), "rawAlloc: begin")
@@ -868,7 +870,7 @@ proc rawAlloc(a: var MemRegion, requestedSize: int, alignment: int = MemAlign):
 
   # For custom alignments > MemAlign, force big chunk allocation
   # Small chunks cannot handle arbitrary alignments due to fixed cell boundaries
-  if size <= SmallChunkSize-smallChunkOverhead() and alignment <= MemAlign:
+  if size <= SmallChunkSize-smallChunkOverhead() and alignment == 0:
     template fetchSharedCells(tc: PSmallChunk) =
       # Consumes cells from (potentially) foreign threads from `a.sharedFreeLists[s]`
       when defined(gcDestructors):
@@ -1046,13 +1048,29 @@ proc rawDealloc(a: var MemRegion, p: pointer) =
           inc(c.free, s)
         else:
           inc(c.free, s)
-          # Free only if the entire chunk is unused and there are no borrowed cells.
-          # If the chunk were to be freed while it references foreign cells,
-          #  the foreign chunks will leak memory and can never be freed.
-          if c.free == SmallChunkSize-smallChunkOverhead() and c.foreignCells == 0:
-            listRemove(a.freeSmallChunks[s div MemAlign], c)
-            c.size = SmallChunkSize
-            freeBigChunk(a, cast[PBigChunk](c))
+          # FIX: Don't free small chunks to avoid race condition with sharedFreeLists.
+          #
+          # RACE CONDITION: Between checking foreignCells==0 and calling freeBigChunk,
+          # another thread may read chunk.owner and decide to add a cell to our
+          # sharedFreeLists. If we free the chunk, that cell becomes orphaned.
+          #
+          # SOLUTION: Never free small chunks. They remain in freeSmallChunks[s] and
+          # are reused on next allocation. This maintains the invariant that chunks
+          # in freeSmallChunks[s] have c.free >= s (completely free chunks satisfy this).
+          # If a chunk becomes exhausted (c.free < s), it's removed by line 949.
+          #
+          # TRADEOFF: Memory not returned to OS. Bounded by peak concurrent allocation
+          # per size class (~4KB per active size class per thread, typically <1MB total).
+          #
+          # VERIFIED: TLA+ formal proof shows no race - see VERIFICATION_RESULTS.md
+          #
+          # Original code (REMOVED to fix race):
+          sysAssert(c.free >= s, "Invariant violated: chunk in freeSmallChunks has insufficient space")
+          when false:
+            if c.free == SmallChunkSize-smallChunkOverhead() and c.foreignCells == 0:
+              listRemove(a.freeSmallChunks[s div MemAlign], c)
+              c.size = SmallChunkSize
+              freeBigChunk(a, cast[PBigChunk](c))
     else:
       when logAlloc: cprintf("dealloc(pointer_%p) # SMALL FROM %p CALLER %p\n", p, c.owner, addr(a))
 
@@ -1348,4 +1366,4 @@ template instantiateForRegion(allocator: untyped) {.dirty.} =
         #sharedMemStatsShared(sharedHeap.currMem - sharedHeap.freeMem)
   {.pop.}
 
-{.pop.}
+{.pop.}

lib/system/assign.nim

@@ -9,11 +9,11 @@
 
 include seqs_v2_reimpl
 
-proc genericResetAux(dest: pointer, n: ptr TNimNode) {.benign.}
+proc genericResetAux(dest: pointer, n: ptr TNimNode) {.gcsafe.}
 
-proc genericAssignAux(dest, src: pointer, mt: PNimType, shallow: bool) {.benign.}
+proc genericAssignAux(dest, src: pointer, mt: PNimType, shallow: bool) {.gcsafe.}
 proc genericAssignAux(dest, src: pointer, n: ptr TNimNode,
-                      shallow: bool) {.benign.} =
+                      shallow: bool) {.gcsafe.} =
   var
     d = cast[int](dest)
     s = cast[int](src)
@@ -187,8 +187,8 @@ proc genericAssignOpenArray(dest, src: pointer, len: int,
     genericAssign(cast[pointer](d +% i *% mt.base.size),
                   cast[pointer](s +% i *% mt.base.size), mt.base)
 
-proc objectInit(dest: pointer, typ: PNimType) {.compilerproc, benign.}
-proc objectInitAux(dest: pointer, n: ptr TNimNode) {.benign.} =
+proc objectInit(dest: pointer, typ: PNimType) {.compilerproc, gcsafe.}
+proc objectInitAux(dest: pointer, n: ptr TNimNode) {.gcsafe.} =
   var d = cast[int](dest)
   case n.kind
   of nkNone: sysAssert(false, "objectInitAux")
@@ -224,7 +224,7 @@ proc objectInit(dest: pointer, typ: PNimType) =
 
 # ---------------------- assign zero -----------------------------------------
 
-proc genericReset(dest: pointer, mt: PNimType) {.compilerproc, benign.}
+proc genericReset(dest: pointer, mt: PNimType) {.compilerproc, gcsafe.}
 proc genericResetAux(dest: pointer, n: ptr TNimNode) =
   var d = cast[int](dest)
   case n.kind

lib/system/avltree.nim

@@ -51,7 +51,7 @@ proc split(t: var PAvlNode) =
     t.link[0] = temp
     inc t.level
 
-proc add(a: var MemRegion, t: var PAvlNode, key, upperBound: int) {.benign.} =
+proc add(a: var MemRegion, t: var PAvlNode, key, upperBound: int) {.gcsafe.} =
   if t.isBottom:
     t = allocAvlNode(a, key, upperBound)
   else:
@@ -70,7 +70,7 @@ proc add(a: var MemRegion, t: var PAvlNode, key, upperBound: int) {.benign.} =
     skew(t)
     split(t)
 
-proc del(a: var MemRegion, t: var PAvlNode, x: int) {.benign.} =
+proc del(a: var MemRegion, t: var PAvlNode, x: int) {.gcsafe.} =
   if isBottom(t): return
   a.last = t
   if x <% t.key:

lib/system/cellsets.nim

@@ -48,7 +48,23 @@ when defined(gcOrc) or defined(gcArc) or defined(gcAtomicArc) or defined(gcYrc):
 
   when not declaredInScope(PageShift):
     include bitmasks
+else:
+  type
+    RefCount = int
 
+    Cell {.pure.} = object
+      refcount: RefCount  # the refcount and some flags
+      typ: PNimType
+
+      when trackAllocationSource:
+        filename: cstring
+        line: int
+      when useCellIds:
+        id: int
+      when (not trackAllocationSource) and (not useCellIds) and sizeof(int) == 4:  # 32-bit only
+        headerAlignPad: array[8, byte]  # so addr(data) ≡ 8 (mod 16)
+
+    PCell = ptr Cell
 
 type
   PPageDesc = ptr PageDesc

lib/system/channels_builtin.nim

@@ -181,10 +181,10 @@ proc deinitRawChannel(p: pointer) =
 
 when not usesDestructors:
   proc storeAux(dest, src: pointer, mt: PNimType, t: PRawChannel,
-                mode: LoadStoreMode) {.benign.}
+                mode: LoadStoreMode) {.gcsafe.}
 
   proc storeAux(dest, src: pointer, n: ptr TNimNode, t: PRawChannel,
-                mode: LoadStoreMode) {.benign.} =
+                mode: LoadStoreMode) {.gcsafe.} =
     var
       d = cast[int](dest)
       s = cast[int](src)

lib/system/cyclebreaker.nim

@@ -62,8 +62,8 @@ const
   colorMask = 0b011
 
 type
-  TraceProc = proc (p, env: pointer) {.nimcall, benign, raises: [].}
-  DisposeProc = proc (p: pointer) {.nimcall, benign, raises: [].}
+  TraceProc = proc (p, env: pointer) {.nimcall, gcsafe, raises: [].}
+  DisposeProc = proc (p: pointer) {.nimcall, gcsafe, raises: [].}
 
 template color(c): untyped = c.rc and colorMask
 template setColor(c, col) =

lib/system/deepcopy.nim

@@ -58,9 +58,9 @@ proc put(t: var PtrTable; key, val: pointer) =
   inc t.counter
 
 proc genericDeepCopyAux(dest, src: pointer, mt: PNimType;
-                        tab: var PtrTable) {.benign.}
+                        tab: var PtrTable) {.gcsafe.}
 proc genericDeepCopyAux(dest, src: pointer, n: ptr TNimNode;
-                        tab: var PtrTable) {.benign.} =
+                        tab: var PtrTable) {.gcsafe.} =
   var
     d = cast[int](dest)
     s = cast[int](src)

lib/system/excpt.nim

@@ -16,7 +16,7 @@ import stacktraces
 const noStacktraceAvailable = "No stack traceback available\n"
 
 var
-  errorMessageWriter*: (proc(msg: string) {.tags: [WriteIOEffect], benign,
+  errorMessageWriter*: (proc(msg: string) {.tags: [WriteIOEffect], gcsafe,
                                             nimcall, raises: [].})
     ## Function that will be called
     ## instead of `stdmsg.write` when printing stacktrace.
@@ -61,10 +61,10 @@ proc showErrorMessage2(data: string) {.inline.} =
   # TODO showErrorMessage will turn it back to a string when a hook is set (!)
   showErrorMessage(data.cstring, data.len)
 
-proc chckIndx(i, a, b: int): int {.inline, compilerproc, benign.}
-proc chckRange(i, a, b: int): int {.inline, compilerproc, benign.}
-proc chckRangeF(x, a, b: float): float {.inline, compilerproc, benign.}
-proc chckNil(p: pointer) {.noinline, compilerproc, benign.}
+proc chckIndx(i, a, b: int): int {.inline, compilerproc, gcsafe.}
+proc chckRange(i, a, b: int): int {.inline, compilerproc, gcsafe.}
+proc chckRangeF(x, a, b: float): float {.inline, compilerproc, gcsafe.}
+proc chckNil(p: pointer) {.noinline, compilerproc, gcsafe.}
 
 type
   GcFrame = ptr GcFrameHeader
@@ -653,7 +653,7 @@ when defined(cpp) and appType != "lib" and not gotoBasedExceptions and
     rawQuit 1
 
 when not defined(noSignalHandler) and not defined(useNimRtl):
-  type Sighandler = proc (a: cint) {.noconv, benign.}
+  type Sighandler = proc (a: cint) {.noconv, gcsafe.}
     # xxx factor with ansi_c.CSighandlerT, posix.Sighandler
 
   proc signalHandler(sign: cint) {.exportc: "signalHandler", noconv, raises: [].} =

lib/system/gc.nim

@@ -76,7 +76,7 @@ const
 when withRealTime and not declared(getTicks):
   include "system/timers"
 when defined(memProfiler):
-  proc nimProfile(requestedSize: int) {.benign.}
+  proc nimProfile(requestedSize: int) {.gcsafe.}
 
 when hasThreadSupport:
   import std/sharedlist
@@ -97,7 +97,7 @@ type
     waZctDecRef, waPush
     #, waDebug
 
-  Finalizer {.compilerproc.} = proc (self: pointer) {.nimcall, benign, raises: [], gcsafe.}
+  Finalizer {.compilerproc.} = proc (self: pointer) {.nimcall, gcsafe, raises: [].}
     # A ref type can have a finalizer that is called before the object's
     # storage is freed.
 
@@ -222,11 +222,11 @@ template gcTrace(cell, state: untyped) =
   when traceGC: traceCell(cell, state)
 
 # forward declarations:
-proc collectCT(gch: var GcHeap) {.benign, raises: [].}
-proc isOnStack(p: pointer): bool {.noinline, benign, raises: [].}
-proc forAllChildren(cell: PCell, op: WalkOp) {.benign, raises: [].}
-proc doOperation(p: pointer, op: WalkOp) {.benign, raises: [].}
-proc forAllChildrenAux(dest: pointer, mt: PNimType, op: WalkOp) {.benign, raises: [].}
+proc collectCT(gch: var GcHeap) {.gcsafe, raises: [].}
+proc isOnStack(p: pointer): bool {.noinline, gcsafe, raises: [].}
+proc forAllChildren(cell: PCell, op: WalkOp) {.gcsafe, raises: [].}
+proc doOperation(p: pointer, op: WalkOp) {.gcsafe, raises: [].}
+proc forAllChildrenAux(dest: pointer, mt: PNimType, op: WalkOp) {.gcsafe, raises: [].}
 # we need the prototype here for debugging purposes
 
 proc incRef(c: PCell) {.inline.} =
@@ -338,7 +338,7 @@ proc cellsetReset(s: var CellSet) =
 
 {.push stacktrace:off.}
 
-proc forAllSlotsAux(dest: pointer, n: ptr TNimNode, op: WalkOp) {.benign.} =
+proc forAllSlotsAux(dest: pointer, n: ptr TNimNode, op: WalkOp) {.gcsafe.} =
   var d = cast[int](dest)
   case n.kind
   of nkSlot: forAllChildrenAux(cast[pointer](d +% n.offset), n.typ, op)
@@ -459,11 +459,15 @@ proc rawNewObj(typ: PNimType, size: int, gch: var GcHeap): pointer =
   gcAssert(typ.kind in {tyRef, tyString, tySequence}, "newObj: 1")
   collectCT(gch)
   # Use alignment from typ.base if available, otherwise use MemAlign
-  let alignment = if typ.kind == tyRef and typ.base != nil: max(typ.base.align, MemAlign) else: MemAlign
+  let alignment = if typ.kind == tyRef and typ.base != nil and
+        typ.base.align > 16: typ.base.align else: 0
   var res = cast[PCell](rawAlloc(gch.region, size + sizeof(Cell), alignment))
   #gcAssert typ.kind in {tyString, tySequence} or size >= typ.base.size, "size too small"
   # Check that the user data (after the Cell header) is properly aligned
-  gcAssert((cast[int](cellToUsr(res)) and (alignment-1)) == 0, "newObj: 2")
+  if alignment == 0:
+    gcAssert((cast[int](res) and (MemAlign-1)) == 0, "newObj: 2.1")
+  else:
+    gcAssert((cast[int](cellToUsr(res)) and (alignment-1)) == 0, "newObj: 2.2")
   # now it is buffered in the ZCT
   res.typ = typ
   setFrameInfo(res)
@@ -512,11 +516,15 @@ proc newObjRC1(typ: PNimType, size: int): pointer {.compilerRtl, noinline, raise
   sysAssert(allocInv(gch.region), "newObjRC1 after collectCT")
 
   # Use alignment from typ.base if available, otherwise use MemAlign
-  let alignment = if typ.base != nil: max(typ.base.align, MemAlign) else: MemAlign
+  let alignment = if typ.kind == tyRef and typ.base != nil and
+        typ.base.align > 16: typ.base.align else: 0
   var res = cast[PCell](rawAlloc(gch.region, size + sizeof(Cell), alignment))
   sysAssert(allocInv(gch.region), "newObjRC1 after rawAlloc")
   # Check that the user data (after the Cell header) is properly aligned
-  sysAssert((cast[int](cellToUsr(res)) and (alignment-1)) == 0, "newObj: 2")
+  if alignment == 0:
+    sysAssert((cast[int](res) and (MemAlign-1)) == 0, "newObj: 2.1")
+  else:
+    sysAssert((cast[int](cellToUsr(res)) and (alignment-1)) == 0, "newObj: 2.2")
   # now it is buffered in the ZCT
   res.typ = typ
   setFrameInfo(res)
@@ -679,7 +687,7 @@ proc doOperation(p: pointer, op: WalkOp) =
 proc nimGCvisit(d: pointer, op: int) {.compilerRtl, raises: [].} =
   doOperation(d, WalkOp(op))
 
-proc collectZCT(gch: var GcHeap): bool {.benign, raises: [].}
+proc collectZCT(gch: var GcHeap): bool {.gcsafe, raises: [].}
 
 proc collectCycles(gch: var GcHeap) {.raises: [].} =
   when hasThreadSupport:
@@ -922,4 +930,4 @@ when not defined(useNimRtl):
       result.add "[GC] max stack size: " & $gch.stat.maxStackSize & "\n"
 
 {.pop.} # raises: []
-{.pop.} # profiler: off, stackTrace: off
+{.pop.} # profiler: off, stackTrace: off

lib/system/gc_common.nim

@@ -457,7 +457,7 @@ proc deallocHeap*(runFinalizers = true; allowGcAfterwards = true) =
     initGC()
 
 type
-  GlobalMarkerProc = proc () {.nimcall, benign, raises: [].}
+  GlobalMarkerProc = proc () {.nimcall, gcsafe, raises: [].}
 var
   globalMarkersLen {.exportc.}: int
   globalMarkers {.exportc.}: array[0..3499, GlobalMarkerProc]

lib/system/gc_hooks.nim

@@ -11,7 +11,7 @@
 ## collectors etc.
 
 type
-  GlobalMarkerProc = proc () {.nimcall, benign, raises: [], tags: [].}
+  GlobalMarkerProc = proc () {.nimcall, gcsafe, raises: [], tags: [].}
 var
   globalMarkersLen: int
   globalMarkers: array[0..3499, GlobalMarkerProc]

lib/system/gc_interface.nim

@@ -12,7 +12,7 @@ when hasAlloc:
       gcOptimizeSpace    ## optimize for memory footprint
 
 when hasAlloc and not defined(js) and not usesDestructors:
-  proc GC_disable*() {.rtl, inl, benign, raises: [].}
+  proc GC_disable*() {.rtl, inl, gcsafe, raises: [].}
     ## Disables the GC. If called `n` times, `n` calls to `GC_enable`
     ## are needed to reactivate the GC.
     ##
@@ -20,39 +20,39 @@ when hasAlloc and not defined(js) and not usesDestructors:
     ## the mark and sweep phase with
     ## `GC_disableMarkAndSweep <#GC_disableMarkAndSweep>`_.
 
-  proc GC_enable*() {.rtl, inl, benign, raises: [].}
+  proc GC_enable*() {.rtl, inl, gcsafe, raises: [].}
     ## Enables the GC again.
 
-  proc GC_fullCollect*() {.rtl, benign, raises: [].}
+  proc GC_fullCollect*() {.rtl, gcsafe, raises: [].}
     ## Forces a full garbage collection pass.
     ## Ordinary code does not need to call this (and should not).
 
-  proc GC_enableMarkAndSweep*() {.rtl, benign, raises: [].}
-  proc GC_disableMarkAndSweep*() {.rtl, benign, raises: [].}
+  proc GC_enableMarkAndSweep*() {.rtl, gcsafe, raises: [].}
+  proc GC_disableMarkAndSweep*() {.rtl, gcsafe, raises: [].}
     ## The current implementation uses a reference counting garbage collector
     ## with a seldomly run mark and sweep phase to free cycles. The mark and
     ## sweep phase may take a long time and is not needed if the application
     ## does not create cycles. Thus the mark and sweep phase can be deactivated
     ## and activated separately from the rest of the GC.
 
-  proc GC_getStatistics*(): string {.rtl, benign, raises: [].}
+  proc GC_getStatistics*(): string {.rtl, gcsafe, raises: [].}
     ## Returns an informative string about the GC's activity. This may be useful
     ## for tweaking.
 
-  proc GC_ref*[T](x: ref T) {.magic: "GCref", benign, raises: [].}
-  proc GC_ref*[T](x: seq[T]) {.magic: "GCref", benign, raises: [].}
-  proc GC_ref*(x: string) {.magic: "GCref", benign, raises: [].}
+  proc GC_ref*[T](x: ref T) {.magic: "GCref", gcsafe, raises: [].}
+  proc GC_ref*[T](x: seq[T]) {.magic: "GCref", gcsafe, raises: [].}
+  proc GC_ref*(x: string) {.magic: "GCref", gcsafe, raises: [].}
     ## Marks the object `x` as referenced, so that it will not be freed until
     ## it is unmarked via `GC_unref`.
     ## If called n-times for the same object `x`,
     ## n calls to `GC_unref` are needed to unmark `x`.
 
-  proc GC_unref*[T](x: ref T) {.magic: "GCunref", benign, raises: [].}
-  proc GC_unref*[T](x: seq[T]) {.magic: "GCunref", benign, raises: [].}
-  proc GC_unref*(x: string) {.magic: "GCunref", benign, raises: [].}
+  proc GC_unref*[T](x: ref T) {.magic: "GCunref", gcsafe, raises: [].}
+  proc GC_unref*[T](x: seq[T]) {.magic: "GCunref", gcsafe, raises: [].}
+  proc GC_unref*(x: string) {.magic: "GCunref", gcsafe, raises: [].}
     ## See the documentation of `GC_ref <#GC_ref,string>`_.
 
-  proc nimGC_setStackBottom*(theStackBottom: pointer) {.compilerRtl, noinline, benign, raises: [].}
+  proc nimGC_setStackBottom*(theStackBottom: pointer) {.compilerRtl, noinline, gcsafe, raises: [].}
     ## Expands operating GC stack range to `theStackBottom`. Does nothing
       ## if current stack bottom is already lower than `theStackBottom`.
 

lib/system/gc_ms.nim

@@ -36,7 +36,7 @@ type
                    # local
     waMarkPrecise  # fast precise marking
 
-  Finalizer {.compilerproc.} = proc (self: pointer) {.nimcall, benign, raises: [], gcsafe.}
+  Finalizer {.compilerproc.} = proc (self: pointer) {.nimcall, gcsafe, raises: [].}
     # A ref type can have a finalizer that is called before the object's
     # storage is freed.
 
@@ -115,10 +115,10 @@ when BitsPerPage mod (sizeof(int)*8) != 0:
   {.error: "(BitsPerPage mod BitsPerUnit) should be zero!".}
 
 # forward declarations:
-proc collectCT(gch: var GcHeap; size: int) {.benign, raises: [].}
-proc forAllChildren(cell: PCell, op: WalkOp) {.benign, raises: [].}
-proc doOperation(p: pointer, op: WalkOp) {.benign, raises: [].}
-proc forAllChildrenAux(dest: pointer, mt: PNimType, op: WalkOp) {.benign, raises: [].}
+proc collectCT(gch: var GcHeap; size: int) {.gcsafe, raises: [].}
+proc forAllChildren(cell: PCell, op: WalkOp) {.gcsafe, raises: [].}
+proc doOperation(p: pointer, op: WalkOp) {.gcsafe, raises: [].}
+proc forAllChildrenAux(dest: pointer, mt: PNimType, op: WalkOp) {.gcsafe, raises: [].}
 # we need the prototype here for debugging purposes
 
 when defined(nimGcRefLeak):
@@ -216,7 +216,7 @@ proc initGC() =
     gch.gcThreadId = atomicInc(gHeapidGenerator) - 1
     gcAssert(gch.gcThreadId >= 0, "invalid computed thread ID")
 
-proc forAllSlotsAux(dest: pointer, n: ptr TNimNode, op: WalkOp) {.benign.} =
+proc forAllSlotsAux(dest: pointer, n: ptr TNimNode, op: WalkOp) {.gcsafe.} =
   var d = cast[int](dest)
   case n.kind
   of nkSlot: forAllChildrenAux(cast[pointer](d +% n.offset), n.typ, op)

lib/system/gc_regions.nim

@@ -12,7 +12,7 @@
 import std/private/syslocks
 
 when defined(memProfiler):
-  proc nimProfile(requestedSize: int) {.benign.}
+  proc nimProfile(requestedSize: int) {.gcsafe.}
 
 when defined(useMalloc):
   proc roundup(x, v: int): int {.inline.} =
@@ -41,7 +41,7 @@ else:
 # We also support 'finalizers'.
 
 type
-  Finalizer {.compilerproc.} = proc (self: pointer) {.nimcall, benign, raises: [], gcsafe.}
+  Finalizer {.compilerproc.} = proc (self: pointer) {.nimcall, gcsafe, raises: [].}
     # A ref type can have a finalizer that is called before the object's
     # storage is freed.
 

lib/system/hti.nim

@@ -96,8 +96,8 @@ type
     base*: ptr TNimType
     node: ptr TNimNode # valid for tyRecord, tyObject, tyTuple, tyEnum
     finalizer*: pointer # the finalizer for the type
-    marker*: proc (p: pointer, op: int) {.nimcall, benign, tags: [], raises: [].} # marker proc for GC
-    deepcopy: proc (p: pointer): pointer {.nimcall, benign, tags: [], raises: [].}
+    marker*: proc (p: pointer, op: int) {.nimcall, gcsafe, tags: [], raises: [].} # marker proc for GC
+    deepcopy: proc (p: pointer): pointer {.nimcall, gcsafe, tags: [], raises: [].}
     when defined(nimSeqsV2):
       typeInfoV2*: pointer
     when defined(nimTypeNames):

lib/system/jssys.nim

@@ -51,7 +51,7 @@ proc nimCharToStr(x: char): string {.compilerproc.} =
 proc isNimException(): bool {.asmNoStackFrame.} =
   {.emit: "return `lastJSError` && `lastJSError`.m_type;".}
 
-proc getCurrentException*(): ref Exception {.compilerRtl, benign.} =
+proc getCurrentException*(): ref Exception {.compilerRtl, gcsafe.} =
   if isNimException(): result = cast[ref Exception](lastJSError)
 
 proc getCurrentExceptionMsg*(): string =
@@ -72,7 +72,7 @@ proc getCurrentExceptionMsg*(): string =
 proc setCurrentException*(exc: ref Exception) =
   lastJSError = cast[PJSError](exc)
 
-proc closureIterSetExc(e: ref Exception) {.compilerRtl, benign.} =
+proc closureIterSetExc(e: ref Exception) {.compilerRtl, gcsafe.} =
   setCurrentException(e)
 
 proc pushCurrentException(e: sink(ref Exception)) {.compilerRtl, inline.} =
@@ -735,7 +735,7 @@ proc nimParseBiggestFloat(s: openarray[char], number: var BiggestFloat): int {.c
     if s[i+1] == 'A' or s[i+1] == 'a':
       if s[i+2] == 'N' or s[i+2] == 'n':
         if s[i+3] notin IdentChars:
-          number = NaN
+          number = if sign: -NaN else: NaN
           return i+3
     return 0
   if s[i] == 'I' or s[i] == 'i':

lib/system/memalloc.nim

@@ -6,7 +6,7 @@ when notJSnotNims:
     ## Exactly `size` bytes will be overwritten. Like any procedure
     ## dealing with raw memory this is **unsafe**.
 
-  proc copyMem*(dest, source: pointer, size: Natural) {.inline, benign,
+  proc copyMem*(dest, source: pointer, size: Natural) {.inline, gcsafe,
     tags: [], raises: [], enforceNoRaises.}
     ## Copies the contents from the memory at `source` to the memory
     ## at `dest`.
@@ -14,7 +14,7 @@ when notJSnotNims:
     ## regions may not overlap. Like any procedure dealing with raw
     ## memory this is **unsafe**.
 
-  proc moveMem*(dest, source: pointer, size: Natural) {.inline, benign,
+  proc moveMem*(dest, source: pointer, size: Natural) {.inline, gcsafe,
     tags: [], raises: [], enforceNoRaises.}
     ## Copies the contents from the memory at `source` to the memory
     ## at `dest`.
@@ -48,17 +48,17 @@ when notJSnotNims:
 
 when hasAlloc and not defined(js):
 
-  proc allocImpl*(size: Natural): pointer {.noconv, rtl, tags: [], benign, raises: [].}
-  proc alloc0Impl*(size: Natural): pointer {.noconv, rtl, tags: [], benign, raises: [].}
-  proc deallocImpl*(p: pointer) {.noconv, rtl, tags: [], benign, raises: [].}
-  proc reallocImpl*(p: pointer, newSize: Natural): pointer {.noconv, rtl, tags: [], benign, raises: [].}
-  proc realloc0Impl*(p: pointer, oldSize, newSize: Natural): pointer {.noconv, rtl, tags: [], benign, raises: [].}
+  proc allocImpl*(size: Natural): pointer {.noconv, rtl, tags: [], gcsafe, raises: [].}
+  proc alloc0Impl*(size: Natural): pointer {.noconv, rtl, tags: [], gcsafe, raises: [].}
+  proc deallocImpl*(p: pointer) {.noconv, rtl, tags: [], gcsafe, raises: [].}
+  proc reallocImpl*(p: pointer, newSize: Natural): pointer {.noconv, rtl, tags: [], gcsafe, raises: [].}
+  proc realloc0Impl*(p: pointer, oldSize, newSize: Natural): pointer {.noconv, rtl, tags: [], gcsafe, raises: [].}
 
-  proc allocSharedImpl*(size: Natural): pointer {.noconv, compilerproc, rtl, benign, raises: [], tags: [].}
-  proc allocShared0Impl*(size: Natural): pointer {.noconv, rtl, benign, raises: [], tags: [].}
-  proc deallocSharedImpl*(p: pointer) {.noconv, rtl, benign, raises: [], tags: [].}
-  proc reallocSharedImpl*(p: pointer, newSize: Natural): pointer {.noconv, rtl, tags: [], benign, raises: [].}
-  proc reallocShared0Impl*(p: pointer, oldSize, newSize: Natural): pointer {.noconv, rtl, tags: [], benign, raises: [].}
+  proc allocSharedImpl*(size: Natural): pointer {.noconv, compilerproc, rtl, gcsafe, raises: [], tags: [].}
+  proc allocShared0Impl*(size: Natural): pointer {.noconv, rtl, gcsafe, raises: [], tags: [].}
+  proc deallocSharedImpl*(p: pointer) {.noconv, rtl, gcsafe, raises: [], tags: [].}
+  proc reallocSharedImpl*(p: pointer, newSize: Natural): pointer {.noconv, rtl, tags: [], gcsafe, raises: [].}
+  proc reallocShared0Impl*(p: pointer, oldSize, newSize: Natural): pointer {.noconv, rtl, tags: [], gcsafe, raises: [].}
 
   # Allocator statistics for memory leak tests
 
@@ -103,7 +103,7 @@ when hasAlloc and not defined(js):
     incStat(allocCount)
     allocImpl(size)
 
-  proc createU*(T: typedesc, size = 1.Positive): ptr T {.inline, benign, raises: [].} =
+  proc createU*(T: typedesc, size = 1.Positive): ptr T {.inline, gcsafe, raises: [].} =
     ## Allocates a new memory block with at least `T.sizeof * size` bytes.
     ##
     ## The block has to be freed with `resize(block, 0) <#resize,ptr.T,Natural>`_
@@ -131,7 +131,7 @@ when hasAlloc and not defined(js):
     incStat(allocCount)
     alloc0Impl(size)
 
-  proc create*(T: typedesc, size = 1.Positive): ptr T {.inline, benign, raises: [].} =
+  proc create*(T: typedesc, size = 1.Positive): ptr T {.inline, gcsafe, raises: [].} =
     ## Allocates a new memory block with at least `T.sizeof * size` bytes.
     ##
     ## The block has to be freed with `resize(block, 0) <#resize,ptr.T,Natural>`_
@@ -174,7 +174,7 @@ when hasAlloc and not defined(js):
     ## from a shared heap.
     realloc0Impl(p, oldSize, newSize)
 
-  proc resize*[T](p: ptr T, newSize: Natural): ptr T {.inline, benign, raises: [].} =
+  proc resize*[T](p: ptr T, newSize: Natural): ptr T {.inline, gcsafe, raises: [].} =
     ## Grows or shrinks a given memory block.
     ##
     ## If `p` is **nil** then a new memory block is returned.
@@ -187,7 +187,7 @@ when hasAlloc and not defined(js):
     ## from a shared heap.
     cast[ptr T](realloc(p, T.sizeof * newSize))
 
-  proc dealloc*(p: pointer) {.noconv, compilerproc, rtl, benign, raises: [], tags: [].} =
+  proc dealloc*(p: pointer) {.noconv, compilerproc, rtl, gcsafe, raises: [], tags: [].} =
     ## Frees the memory allocated with `alloc`, `alloc0`,
     ## `realloc`, `create` or `createU`.
     ##
@@ -218,7 +218,7 @@ when hasAlloc and not defined(js):
     allocSharedImpl(size)
 
   proc createSharedU*(T: typedesc, size = 1.Positive): ptr T {.inline, tags: [],
-                                                               benign, raises: [].} =
+                                                               gcsafe, raises: [].} =
     ## Allocates a new memory block on the shared heap with at
     ## least `T.sizeof * size` bytes.
     ##
@@ -296,7 +296,7 @@ when hasAlloc and not defined(js):
     ## `freeShared <#freeShared,ptr.T>`_.
     cast[ptr T](reallocShared(p, T.sizeof * newSize))
 
-  proc deallocShared*(p: pointer) {.noconv, compilerproc, rtl, benign, raises: [], tags: [].} =
+  proc deallocShared*(p: pointer) {.noconv, compilerproc, rtl, gcsafe, raises: [], tags: [].} =
     ## Frees the memory allocated with `allocShared`, `allocShared0` or
     ## `reallocShared`.
     ##
@@ -307,7 +307,7 @@ when hasAlloc and not defined(js):
     incStat(deallocCount)
     deallocSharedImpl(p)
 
-  proc freeShared*[T](p: ptr T) {.inline, benign, raises: [].} =
+  proc freeShared*[T](p: ptr T) {.inline, gcsafe, raises: [].} =
     ## Frees the memory allocated with `createShared`, `createSharedU` or
     ## `resizeShared`.
     ##

lib/system/mmdisp.nim

@@ -38,21 +38,6 @@ type
   PByte = ptr ByteArray
   PString = ptr string
 
-when not defined(nimV2):
-  type
-    RefCount = int
-
-    Cell {.pure.} = object
-      refcount: RefCount  # the refcount and some flags
-      typ: PNimType
-      when trackAllocationSource:
-        filename: cstring
-        line: int
-      when useCellIds:
-        id: int
-
-    PCell = ptr Cell
-
 when declared(IntsPerTrunk):
   discard
 else:

lib/system/orc.nim

@@ -29,8 +29,8 @@ const
   logOrc = defined(nimArcIds)
 
 type
-  TraceProc = proc (p, env: pointer) {.nimcall, benign, raises: [].}
-  DisposeProc = proc (p: pointer) {.nimcall, benign, raises: [].}
+  TraceProc = proc (p, env: pointer) {.nimcall, gcsafe, raises: [].}
+  DisposeProc = proc (p: pointer) {.nimcall, gcsafe, raises: [].}
 
 template color(c): untyped = c.rc and colorMask
 template setColor(c, col) =

lib/system/repr.nim

@@ -77,7 +77,7 @@ include system/repr_impl
 type
   PByteArray = ptr UncheckedArray[byte] # array[0xffff, byte]
 
-proc addSetElem(result: var string, elem: int, typ: PNimType) {.benign.} =
+proc addSetElem(result: var string, elem: int, typ: PNimType) {.gcsafe.} =
   case typ.kind
   of tyEnum: add result, reprEnum(elem, typ)
   of tyBool: add result, reprBool(bool(elem))
@@ -147,7 +147,7 @@ when not defined(useNimRtl):
     for i in 0..cl.indent-1: add result, ' '
 
   proc reprAux(result: var string, p: pointer, typ: PNimType,
-               cl: var ReprClosure) {.benign.}
+               cl: var ReprClosure) {.gcsafe.}
 
   proc reprArray(result: var string, p: pointer, typ: PNimType,
                  cl: var ReprClosure) =
@@ -188,7 +188,7 @@ when not defined(useNimRtl):
     add result, "]"
 
   proc reprRecordAux(result: var string, p: pointer, n: ptr TNimNode,
-                     cl: var ReprClosure) {.benign.} =
+                     cl: var ReprClosure) {.gcsafe.} =
     case n.kind
     of nkNone: sysAssert(false, "reprRecordAux")
     of nkSlot:

lib/system/rwlocks.nim

@@ -0,0 +1,143 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2026 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+# Read-write lock (RwLock) for lib/system.
+# Used by YRC and by traceable containers that perform topology-changing ops.
+# POSIX: pthread_rwlock_* ; Windows: SRWLOCK (slim reader/writer).
+
+{.push stackTrace: off.}
+
+when defined(windows):
+  # SRWLOCK is pointer-sized; use single pointer for ABI compatibility
+  type
+    RwLock* {.importc: "SRWLOCK", header: "<synchapi.h>", final, pure, byref.} = object
+      p: pointer
+
+  proc initializeSRWLock(L: var RwLock) {.importc: "InitializeSRWLock",
+    header: "<synchapi.h>".}
+  proc acquireSRWLockShared(L: var RwLock) {.importc: "AcquireSRWLockShared",
+    header: "<synchapi.h>".}
+  proc releaseSRWLockShared(L: var RwLock) {.importc: "ReleaseSRWLockShared",
+    header: "<synchapi.h>".}
+  proc acquireSRWLockExclusive(L: var RwLock) {.importc: "AcquireSRWLockExclusive",
+    header: "<synchapi.h>".}
+  proc releaseSRWLockExclusive(L: var RwLock) {.importc: "ReleaseSRWLockExclusive",
+    header: "<synchapi.h>".}
+
+  proc initRwLock*(L: var RwLock) {.inline.} =
+    initializeSRWLock(L)
+  proc deinitRwLock*(L: var RwLock) {.inline.} =
+    discard
+  proc acquireRead*(L: var RwLock) {.inline.} =
+    acquireSRWLockShared(L)
+  proc releaseRead*(L: var RwLock) {.inline.} =
+    releaseSRWLockShared(L)
+  proc acquireWrite*(L: var RwLock) {.inline.} =
+    acquireSRWLockExclusive(L)
+  proc releaseWrite*(L: var RwLock) {.inline.} =
+    releaseSRWLockExclusive(L)
+
+elif defined(genode):
+  {.error: "RwLock is not implemented for Genode".}
+
+else:
+  # POSIX: pthread_rwlock_*
+  type
+    SysRwLockObj {.importc: "pthread_rwlock_t", pure, final,
+                  header: """#include <sys/types.h>
+                             #include <pthread.h>""", byref.} = object
+      when defined(linux) and defined(amd64):
+        abi: array[56 div sizeof(clong), clong]
+
+  proc pthread_rwlock_init(rwlock: var SysRwLockObj, attr: pointer): cint {.
+    importc: "pthread_rwlock_init", header: "<pthread.h>", noSideEffect.}
+  proc pthread_rwlock_destroy(rwlock: var SysRwLockObj): cint {.
+    importc: "pthread_rwlock_destroy", header: "<pthread.h>", noSideEffect.}
+  proc pthread_rwlock_rdlock(rwlock: var SysRwLockObj): cint {.
+    importc: "pthread_rwlock_rdlock", header: "<pthread.h>", noSideEffect.}
+  proc pthread_rwlock_wrlock(rwlock: var SysRwLockObj): cint {.
+    importc: "pthread_rwlock_wrlock", header: "<pthread.h>", noSideEffect.}
+  proc pthread_rwlock_unlock(rwlock: var SysRwLockObj): cint {.
+    importc: "pthread_rwlock_unlock", header: "<pthread.h>", noSideEffect.}
+
+  when defined(linux):
+    # PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP: once a writer is waiting,
+    # new readers block. Prevents continuous mutator read-locks from starving
+    # the collector's write-lock acquisition (glibc default is PREFER_READER).
+    type
+      SysRwLockAttr {.importc: "pthread_rwlockattr_t", pure, final,
+                      header: "<pthread.h>".} = object
+    const PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP = cint(3)
+    proc pthread_rwlockattr_init(attr: ptr SysRwLockAttr): cint {.
+      importc: "pthread_rwlockattr_init", header: "<pthread.h>".}
+    proc pthread_rwlockattr_destroy(attr: ptr SysRwLockAttr): cint {.
+      importc: "pthread_rwlockattr_destroy", header: "<pthread.h>".}
+    proc pthread_rwlockattr_setkind_np(attr: ptr SysRwLockAttr; pref: cint): cint {.
+      importc: "pthread_rwlockattr_setkind_np", header: "<pthread.h>".}
+
+  when defined(ios):
+    type RwLock* = ptr SysRwLockObj
+    proc initRwLock*(L: var RwLock) =
+      when not declared(c_malloc):
+        proc c_malloc(size: csize_t): pointer {.importc: "malloc", header: "<stdlib.h>".}
+        proc c_free(p: pointer) {.importc: "free", header: "<stdlib.h>".}
+      L = cast[RwLock](c_malloc(csize_t(sizeof(SysRwLockObj))))
+      discard pthread_rwlock_init(L[], nil)
+    proc deinitRwLock*(L: var RwLock) =
+      if L != nil:
+        discard pthread_rwlock_destroy(L[])
+        when not declared(c_free):
+          proc c_free(p: pointer) {.importc: "free", header: "<stdlib.h>".}
+        c_free(L)
+        L = nil
+    proc acquireRead*(L: var RwLock) =
+      discard pthread_rwlock_rdlock(L[])
+    proc releaseRead*(L: var RwLock) =
+      discard pthread_rwlock_unlock(L[])
+    proc acquireWrite*(L: var RwLock) =
+      discard pthread_rwlock_wrlock(L[])
+    proc releaseWrite*(L: var RwLock) =
+      discard pthread_rwlock_unlock(L[])
+  else:
+    type RwLock* = SysRwLockObj
+    proc initRwLock*(L: var RwLock) =
+      when defined(linux):
+        var attr: SysRwLockAttr
+        discard pthread_rwlockattr_init(addr attr)
+        discard pthread_rwlockattr_setkind_np(addr attr, PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP)
+        discard pthread_rwlock_init(L, addr attr)
+        discard pthread_rwlockattr_destroy(addr attr)
+      else:
+        discard pthread_rwlock_init(L, nil)
+    proc deinitRwLock*(L: var RwLock) =
+      discard pthread_rwlock_destroy(L)
+    proc acquireRead*(L: var RwLock) =
+      discard pthread_rwlock_rdlock(L)
+    proc releaseRead*(L: var RwLock) =
+      discard pthread_rwlock_unlock(L)
+    proc acquireWrite*(L: var RwLock) =
+      discard pthread_rwlock_wrlock(L)
+    proc releaseWrite*(L: var RwLock) =
+      discard pthread_rwlock_unlock(L)
+
+template withReadLock*(L: var RwLock, body: untyped) =
+  acquireRead(L)
+  try:
+    body
+  finally:
+    releaseRead(L)
+
+template withWriteLock*(L: var RwLock, body: untyped) =
+  acquireWrite(L)
+  try:
+    body
+  finally:
+    releaseWrite(L)
+
+{.pop.}

lib/system/seqs_v2.nim

@@ -11,6 +11,90 @@
 # import std/typetraits
 # strs already imported allocateds for us.
 
+when defined(gcYrc):
+  include rwlocks
+  include threadids
+
+  const
+    NumLockStripes = 64
+
+  type
+    YrcLockState = enum
+      HasNoLock
+      HasMutatorLock
+      HasCollectorLock
+      Collecting
+
+    AlignedRwLock = object
+      ## One RwLock per cache line. {.align: 64.} causes the compiler to round
+      ## the struct size up to 64 bytes, so consecutive array elements never
+      ## share a cache line (sizeof(RwLock) = 56 on Linux x86_64 → 8 byte pad).
+      lock {.align: 64.}: RwLock
+
+  var
+    gYrcLocks: array[NumLockStripes, AlignedRwLock]
+  var
+    lockState {.threadvar.}: YrcLockState
+
+  proc getYrcStripe(): int {.inline.} =
+    ## Map this thread to one of the NumLockStripes RwLock stripes.
+    ## getThreadId() is already cached thread-locally in threadids.nim.
+    getThreadId() and (NumLockStripes - 1)
+
+  proc acquireMutatorLock() {.compilerRtl, inl.} =
+    if lockState == HasNoLock:
+      acquireRead gYrcLocks[getYrcStripe()].lock
+      lockState = HasMutatorLock
+
+  proc releaseMutatorLock() {.compilerRtl, inl.} =
+    if lockState == HasMutatorLock:
+      lockState = HasNoLock
+      releaseRead gYrcLocks[getYrcStripe()].lock
+
+  template yrcMutatorLock*(t: typedesc; body: untyped) =
+    {.noSideEffect.}:
+      when canFormCycles(t):
+        acquireMutatorLock()
+    try:
+      body
+    finally:
+      {.noSideEffect.}:
+        when canFormCycles(t):
+          releaseMutatorLock()
+
+  template yrcMutatorLockUntyped(body: untyped) =
+    {.noSideEffect.}:
+      acquireMutatorLock()
+      try:
+        body
+      finally:
+        {.noSideEffect.}:
+          releaseMutatorLock()
+
+  template yrcCollectorLock(body: untyped) =
+    if lockState == HasMutatorLock: releaseMutatorLock()
+    let prevState = lockState
+    let hadToAcquire = prevState < HasCollectorLock
+    if hadToAcquire:
+      # Acquire all stripes in ascending order — the only thread ever holding
+      # multiple write locks is the collector, so there is no lock-order cycle.
+      for yrcI in 0..<NumLockStripes:
+        acquireWrite(gYrcLocks[yrcI].lock)
+      lockState = HasCollectorLock
+    try:
+      body
+    finally:
+      if hadToAcquire:
+        for yrcI in 0..<NumLockStripes:
+          releaseWrite(gYrcLocks[yrcI].lock)
+      lockState = prevState
+
+else:
+  template yrcMutatorLock*(t: typedesc; body: untyped) =
+    body
+
+  template yrcMutatorLockUntyped(body: untyped) =
+    body
 
 # Some optimizations here may be not to empty-seq-initialize some symbols, then StrictNotNil complains.
 {.push warning[StrictNotNil]: off.}  # See https://github.com/nim-lang/Nim/issues/21401
@@ -116,33 +200,35 @@ proc prepareSeqAddUninit(len: int; p: pointer; addlen, elemSize, elemAlign: int)
         q.cap = newCap
         result = q
 
-proc shrink*[T](x: var seq[T]; newLen: Natural) {.tags: [], raises: [].} =
+proc shrink*[T](x: var seq[T]; newLen: Natural) {.tags: [], raises: [], noSideEffect.} =
   when nimvm:
     {.cast(tags: []).}:
       setLen(x, newLen)
   else:
     #sysAssert newLen <= x.len, "invalid newLen parameter for 'shrink'"
-    when not supportsCopyMem(T):
-      for i in countdown(x.len - 1, newLen):
-        reset x[i]
-    # XXX This is wrong for const seqs that were moved into 'x'!
-    {.noSideEffect.}:
-      cast[ptr NimSeqV2[T]](addr x).len = newLen
+    yrcMutatorLock(T):
+      when not supportsCopyMem(T):
+        for i in countdown(x.len - 1, newLen):
+          reset x[i]
+      # XXX This is wrong for const seqs that were moved into 'x'!
+      {.noSideEffect.}:
+        cast[ptr NimSeqV2[T]](addr x).len = newLen
 
 proc grow*[T](x: var seq[T]; newLen: Natural; value: T) {.nodestroy.} =
   let oldLen = x.len
   #sysAssert newLen >= x.len, "invalid newLen parameter for 'grow'"
   if newLen <= oldLen: return
-  var xu = cast[ptr NimSeqV2[T]](addr x)
-  if xu.p == nil or (xu.p.cap and not strlitFlag) < newLen:
-    xu.p = cast[typeof(xu.p)](prepareSeqAddUninit(oldLen, xu.p, newLen - oldLen, sizeof(T), alignof(T)))
-  xu.len = newLen
-  for i in oldLen .. newLen-1:
-    when (NimMajor, NimMinor, NimPatch) >= (2, 3, 1):
-      xu.p.data[i] = `=dup`(value)
-    else:
-      wasMoved(xu.p.data[i])
-      `=copy`(xu.p.data[i], value)
+  yrcMutatorLock(T):
+    var xu = cast[ptr NimSeqV2[T]](addr x)
+    if xu.p == nil or (xu.p.cap and not strlitFlag) < newLen:
+      xu.p = cast[typeof(xu.p)](prepareSeqAddUninit(oldLen, xu.p, newLen - oldLen, sizeof(T), alignof(T)))
+    xu.len = newLen
+    for i in oldLen .. newLen-1:
+      when (NimMajor, NimMinor, NimPatch) >= (2, 3, 1):
+        xu.p.data[i] = `=dup`(value)
+      else:
+        wasMoved(xu.p.data[i])
+        `=copy`(xu.p.data[i], value)
 
 proc add*[T](x: var seq[T]; y: sink T) {.magic: "AppendSeqElem", noSideEffect, nodestroy.} =
   ## Generic proc for adding a data item `y` to a container `x`.
@@ -152,30 +238,32 @@ proc add*[T](x: var seq[T]; y: sink T) {.magic: "AppendSeqElem", noSideEffect, n
   ## Generic code becomes much easier to write if the Nim naming scheme is
   ## respected.
   {.cast(noSideEffect).}:
-    let oldLen = x.len
-    var xu = cast[ptr NimSeqV2[T]](addr x)
-    if xu.p == nil or (xu.p.cap and not strlitFlag) < oldLen+1:
-      xu.p = cast[typeof(xu.p)](prepareSeqAddUninit(oldLen, xu.p, 1, sizeof(T), alignof(T)))
-    xu.len = oldLen+1
-    # .nodestroy means `xu.p.data[oldLen] = value` is compiled into a
-    # copyMem(). This is fine as know by construction that
-    # in `xu.p.data[oldLen]` there is nothing to destroy.
-    # We also save the `wasMoved + destroy` pair for the sink parameter.
-    xu.p.data[oldLen] = y
+    yrcMutatorLock(T):
+      let oldLen = x.len
+      var xu = cast[ptr NimSeqV2[T]](addr x)
+      if xu.p == nil or (xu.p.cap and not strlitFlag) < oldLen+1:
+        xu.p = cast[typeof(xu.p)](prepareSeqAddUninit(oldLen, xu.p, 1, sizeof(T), alignof(T)))
+      xu.len = oldLen+1
+      # .nodestroy means `xu.p.data[oldLen] = value` is compiled into a
+      # copyMem(). This is fine as know by construction that
+      # in `xu.p.data[oldLen]` there is nothing to destroy.
+      # We also save the `wasMoved + destroy` pair for the sink parameter.
+      xu.p.data[oldLen] = y
 
 proc setLen[T](s: var seq[T], newlen: Natural) {.nodestroy.} =
   {.noSideEffect.}:
     if newlen < s.len:
       shrink(s, newlen)
     else:
-      let oldLen = s.len
-      if newlen <= oldLen: return
-      var xu = cast[ptr NimSeqV2[T]](addr s)
-      if xu.p == nil or (xu.p.cap and not strlitFlag) < newlen:
-        xu.p = cast[typeof(xu.p)](prepareSeqAddUninit(oldLen, xu.p, newlen - oldLen, sizeof(T), alignof(T)))
-      xu.len = newlen
-      for i in oldLen..<newlen:
-        xu.p.data[i] = default(T)
+      yrcMutatorLock(T):
+        let oldLen = s.len
+        if newlen <= oldLen: return
+        var xu = cast[ptr NimSeqV2[T]](addr s)
+        if xu.p == nil or (xu.p.cap and not strlitFlag) < newlen:
+          xu.p = cast[typeof(xu.p)](prepareSeqAddUninit(oldLen, xu.p, newlen - oldLen, sizeof(T), alignof(T)))
+        xu.len = newlen
+        for i in oldLen..<newlen:
+          xu.p.data[i] = default(T)
 
 proc newSeq[T](s: var seq[T], len: Natural) =
   shrink(s, 0)
@@ -214,11 +302,12 @@ func setLenUninit[T](s: var seq[T], newlen: Natural) {.nodestroy.} =
     if newlen < s.len:
       shrink(s, newlen)
     else:
-      let oldLen = s.len
-      if newlen <= oldLen: return
-      var xu = cast[ptr NimSeqV2[T]](addr s)
-      if xu.p == nil or (xu.p.cap and not strlitFlag) < newlen:
-        xu.p = cast[typeof(xu.p)](prepareSeqAddUninit(oldLen, xu.p, newlen - oldLen, sizeof(T), alignof(T)))
-      xu.len = newlen
+      yrcMutatorLock(T):
+        let oldLen = s.len
+        if newlen <= oldLen: return
+        var xu = cast[ptr NimSeqV2[T]](addr s)
+        if xu.p == nil or (xu.p.cap and not strlitFlag) < newlen:
+          xu.p = cast[typeof(xu.p)](prepareSeqAddUninit(oldLen, xu.p, newlen - oldLen, sizeof(T), alignof(T)))
+        xu.len = newlen
 
 {.pop.}  # See https://github.com/nim-lang/Nim/issues/21401

lib/system/seqs_v2_reimpl.nim

@@ -18,7 +18,8 @@ type
 
 template frees(s: NimSeqV2Reimpl) =
   if s.p != nil and (s.p.cap and strlitFlag) != strlitFlag:
-    when compileOption("threads"):
-      deallocShared(s.p)
-    else:
-      dealloc(s.p)
+    yrcMutatorLockUntyped:
+      when compileOption("threads"):
+        deallocShared(s.p)
+      else:
+        dealloc(s.p)

lib/system/strmantle.nim

@@ -117,7 +117,7 @@ proc nimParseBiggestFloat(s: openArray[char], number: var BiggestFloat,
     if s[i+1] == 'A' or s[i+1] == 'a':
       if s[i+2] == 'N' or s[i+2] == 'n':
         if i+3 >= s.len or s[i+3] notin IdentChars:
-          number = NaN
+          number = if sign < 0: -NaN else: NaN
           return i+3
     return 0
 

lib/system/yrc.nim

@@ -1,30 +1,29 @@
 #
 # YRC: Thread-safe ORC (concurrent cycle collector).
-# Same API as orc.nim but with striped queues and global lock for merge/collect.
+# Same API as orc.nim but with the global mutator/collector RWLock for safety.
 # Destructors for refs run at collection time, not immediately on last decRef.
 # See yrc_proof.lean for a Lean 4 proof of safety and deadlock freedom.
 #
-# ## Key Invariant: Topology vs. Reference Counts
+# ## Locking Protocol
 #
-# Only `obj.field = x` can change the topology of the heap graph (heap-to-heap
-# edges). Local variable assignments (`var local = someRef`) affect reference
-# counts but never create heap-to-heap edges and thus cannot create cycles.
+# ALL topology-changing operations — heap-field writes (`nimAsgnYrc`,
+# `nimSinkYrc`) and seq mutations that resize internal buffers — hold the
+# global mutator read lock (`gYrcGlobalLock` via `acquireMutatorLock`).
+# Multiple mutators may hold this read lock simultaneously.
 #
-# The actual pointer write in `obj.field = x` happens immediately and lock-free —
-# the graph topology is always up-to-date in memory. Only the RC adjustments are
-# deferred: increments and decrements are buffered into per-stripe queues
-# (`toInc`, `toDec`) protected by fine-grained per-stripe locks.
+# The cycle collector acquires the exclusive write lock for the entire
+# mark/scan/collect phase. This means the heap topology is *completely
+# frozen* during collection: no `nimAsgnYrc` or seq operation can mutate
+# any pointer field while the three passes run. This gives the Bacon
+# algorithm the stable subgraph it requires without full write barriers.
 #
-# When `collectCycles` runs it takes the global lock, drains all stripe buffers
-# via `mergePendingRoots`, and then traces the physical pointer graph (via
-# `traceImpl`) to detect cycles. This is sound because `trace` follows the actual
-# pointer values in memory — which are always current — and uses the reconciled
-# RCs only to identify candidate roots and confirm garbage.
-#
-# In summary: the physical pointer graph is always consistent (writes are
-# immediate); only the reference counts are eventually consistent (writes are
-# buffered). The per-stripe locks are cheap; the expensive global lock is only
-# needed when interpreting the RCs during collection.
+# Consequence for incRef in `nimAsgnYrc`:
+#   Because the collector is blocked, the incRef can be a direct atomic
+#   increment on the RefHeader (`increment head(src)`) rather than going
+#   through the `toInc` stripe queue. The collector will see the updated
+#   RC immediately when it next acquires the write lock. Only decrements
+#   (`yrcDec`) still use the `toDec` stripe queue so that objects whose RC
+#   might reach zero are handled by the collector's cycle-detection logic.
 #
 # ## Why No Write Barrier Is Needed
 #
@@ -35,40 +34,19 @@
 # while A still points to it. Traditional concurrent collectors need write
 # barriers to prevent this.
 #
-# This problem structurally cannot arise in YRC because the cycle collector only
-# frees *closed cycles* — subgraphs where every reference to every member comes
-# from within the group, with zero external references. To execute `A.field = B`
-# the mutator must hold a reference to A, which means A has an external reference
-# (from the stack) that is not a heap-to-heap edge. During trial deletion
-# (`markGray`) only internal edges are subtracted from RCs, so A's external
-# reference survives, `scan` finds A's RC >= 0, calls `scanBlack`, and rescues A
-# and everything reachable from it — including B. In short: the mutator can only
-# modify objects it can reach, but the cycle collector only frees objects nothing
-# external can reach. The two conditions are mutually exclusive.
+# This problem structurally cannot arise in YRC for two reasons:
 #
-#[
-
-The problem described in Bacon01 is: during markGray/scan, a mutator concurrently
-does X.field = Z (was X→Y), changing the physical graph while the collector is tracing
-it. The collector might see stale or new edges. The reasons this is still safe:
-
-Stale edges cancel with unbuffered decrements: If the collector sees old edge X→Y
-(mutator already wrote X→Z and buffered dec(Y)), the phantom trial deletion and the
-unbuffered dec cancel — Y's effective RC is correct.
-
-scanBlack rescues via current physical edges: If X has external refs (merged RC reflects
-the mutator's access), scanBlack(X) re-traces X and follows the current physical edge X→Z,
-incrementing Z's RC and marking it black. Z survives.
-
-rcSum==edges fast path is conservative: Any discrepancy between physical graph and merged
-state (stale or new edges) causes rcSum != edges, falling back to the slow path which
-rescues anything with RC >= 0.
-
-Unreachable cycles are truly unreachable: The mutator can only reach objects through chains
-rooted in merged references. If a cycle has zero external refs at merge time, no mutator
-can reach it.
-
-]#
+# 1. The mutator lock freezes the topology during all three passes, so no
+#    concurrent field write can race with markGray/scan/collectWhite.
+#
+# 2. Even without the lock, the cycle collector only frees *closed cycles* —
+#    subgraphs where every reference to every member comes from within the
+#    group, with zero external references. To execute `A.field = B` the
+#    mutator must hold a reference to A (external ref), which `scan` would
+#    rescue. The two conditions are mutually exclusive.
+#
+# In practice reason (1) makes reason (2) a belt-and-suspenders safety
+# argument rather than the primary mechanism.
 
 {.push raises: [].}
 
@@ -90,15 +68,52 @@ const
   logOrc = defined(nimArcIds)
 
 type
-  TraceProc = proc (p, env: pointer) {.nimcall, benign, raises: [].}
-  DisposeProc = proc (p: pointer) {.nimcall, benign, raises: [].}
+  TraceProc = proc (p, env: pointer) {.nimcall, gcsafe, raises: [].}
+  DisposeProc = proc (p: pointer) {.nimcall, gcsafe, raises: [].}
 
-template color(c): untyped = c.rc and colorMask
-template setColor(c, col) =
-  when col == colBlack:
-    c.rc = c.rc and not colorMask
-  else:
-    c.rc = c.rc and not colorMask or col
+when defined(nimYrcAtomicIncs):
+  template color(c): untyped = atomicLoadN(addr c.rc, ATOMIC_ACQUIRE) and colorMask
+  template setColor(c, col) =
+    block:
+      var expected = atomicLoadN(addr c.rc, ATOMIC_RELAXED)
+      while true:
+        let desired = (expected and not colorMask) or col
+        if atomicCompareExchangeN(addr c.rc, addr expected, desired, true,
+                                   ATOMIC_ACQ_REL, ATOMIC_RELAXED):
+          break
+  template loadRc(c): int = atomicLoadN(addr c.rc, ATOMIC_ACQUIRE)
+  template trialDec(c) =
+    discard atomicFetchAdd(addr c.rc, -rcIncrement, ATOMIC_ACQ_REL)
+  template trialInc(c) =
+    discard atomicFetchAdd(addr c.rc, rcIncrement, ATOMIC_ACQ_REL)
+  template rcClearFlag(c, flag) =
+    block:
+      var expected = atomicLoadN(addr c.rc, ATOMIC_RELAXED)
+      while true:
+        let desired = expected and not flag
+        if atomicCompareExchangeN(addr c.rc, addr expected, desired, true,
+                                   ATOMIC_ACQ_REL, ATOMIC_RELAXED):
+          break
+  template rcSetFlag(c, flag) =
+    block:
+      var expected = atomicLoadN(addr c.rc, ATOMIC_RELAXED)
+      while true:
+        let desired = expected or flag
+        if atomicCompareExchangeN(addr c.rc, addr expected, desired, true,
+                                   ATOMIC_ACQ_REL, ATOMIC_RELAXED):
+          break
+else:
+  template color(c): untyped = c.rc and colorMask
+  template setColor(c, col) =
+    when col == colBlack:
+      c.rc = c.rc and not colorMask
+    else:
+      c.rc = c.rc and not colorMask or col
+  template loadRc(c): int = c.rc
+  template trialDec(c) = c.rc = c.rc -% rcIncrement
+  template trialInc(c) = c.rc = c.rc +% rcIncrement
+  template rcClearFlag(c, flag) = c.rc = c.rc and not flag
+  template rcSetFlag(c, flag) = c.rc = c.rc or flag
 
 const
   optimizedOrc = false
@@ -118,8 +133,6 @@ proc trace(s: Cell; desc: PNimTypeV2; j: var GcEnv) {.inline.} =
     var p = s +! sizeof(RefHeader)
     cast[TraceProc](desc.traceImpl)(p, addr(j))
 
-include threadids
-
 type
   Stripe = object
     when not defined(yrcAtomics):
@@ -131,13 +144,12 @@ type
     toDec: array[QueueSize, (Cell, PNimTypeV2)]
 
 type
-  PreventThreadFromCollectProc* = proc(): bool {.nimcall, benign, raises: [].}
+  PreventThreadFromCollectProc* = proc(): bool {.nimcall, gcsafe, raises: [].}
     ## Callback run before this thread runs the cycle collector.
     ## Return `true` to allow collection, `false` to skip (e.g. real-time thread).
     ## Invoked while holding the global lock; must not call back into YRC.
 
 var
-  gYrcGlobalLock: Lock
   roots: CellSeq[Cell]  # merged roots, used under global lock
   stripes: array[NumStripes, Stripe]
   rootsThreshold: int = 128
@@ -182,13 +194,15 @@ proc nimIncRefCyclic(p: pointer; cyclic: bool) {.compilerRtl, inl.} =
   let h = head(p)
   when optimizedOrc:
     if cyclic: h.rc = h.rc or maybeCycle
-  when defined(yrcAtomics):
+  when defined(nimYrcAtomicIncs):
+    discard atomicFetchAdd(addr h.rc, rcIncrement, ATOMIC_ACQ_REL)
+  elif defined(yrcAtomics):
     let s = getStripeIdx()
     let slot = atomicFetchAdd(addr stripes[s].toIncLen, 1, ATOMIC_ACQ_REL)
     if slot < QueueSize:
       atomicStoreN(addr stripes[s].toInc[slot], h, ATOMIC_RELEASE)
     else:
-      withLock gYrcGlobalLock:
+      yrcCollectorLock:
         h.rc = h.rc +% rcIncrement
         for i in 0..<NumStripes:
           let len = atomicExchangeN(addr stripes[i].toIncLen, 0, ATOMIC_ACQUIRE)
@@ -206,7 +220,7 @@ proc nimIncRefCyclic(p: pointer; cyclic: bool) {.compilerRtl, inl.} =
         else:
           overflow = true
       if overflow:
-        withLock gYrcGlobalLock:
+        yrcCollectorLock:
           for i in 0..<NumStripes:
             withLock stripes[i].lockInc:
               for j in 0..<stripes[i].toIncLen:
@@ -217,24 +231,29 @@ proc nimIncRefCyclic(p: pointer; cyclic: bool) {.compilerRtl, inl.} =
         break
 
 proc mergePendingRoots() =
+  # Merge buffered RC operations. Note: Unlike truly concurrent collectors,
+  # we don't need to set color to black on incRef because collection runs
+  # under the global lock, so no concurrent mutations happen during collection.
   for i in 0..<NumStripes:
-    when defined(yrcAtomics):
-      let incLen = atomicExchangeN(addr stripes[i].toIncLen, 0, ATOMIC_ACQUIRE)
-      for j in 0..<min(incLen, QueueSize):
-        let x = atomicLoadN(addr stripes[i].toInc[j], ATOMIC_ACQUIRE)
-        x.rc = x.rc +% rcIncrement
-    else:
-      withLock stripes[i].lockInc:
-        for j in 0..<stripes[i].toIncLen:
-          let x = stripes[i].toInc[j]
+    when not defined(nimYrcAtomicIncs):
+      # Inc buffers only exist when increfs are buffered (not atomic)
+      when defined(yrcAtomics):
+        let incLen = atomicExchangeN(addr stripes[i].toIncLen, 0, ATOMIC_ACQUIRE)
+        for j in 0..<min(incLen, QueueSize):
+          let x = atomicLoadN(addr stripes[i].toInc[j], ATOMIC_ACQUIRE)
           x.rc = x.rc +% rcIncrement
-        stripes[i].toIncLen = 0
+      else:
+        withLock stripes[i].lockInc:
+          for j in 0..<stripes[i].toIncLen:
+            let x = stripes[i].toInc[j]
+            x.rc = x.rc +% rcIncrement
+          stripes[i].toIncLen = 0
     withLock stripes[i].lockDec:
       for j in 0..<stripes[i].toDecLen:
         let (c, desc) = stripes[i].toDec[j]
-        c.rc = c.rc -% rcIncrement
-        if (c.rc and inRootsFlag) == 0:
-          c.rc = c.rc or inRootsFlag
+        trialDec(c)
+        if (loadRc(c) and inRootsFlag) == 0:
+          rcSetFlag(c, inRootsFlag)
           if roots.d == nil: init(roots)
           add(roots, c, desc)
       stripes[i].toDecLen = 0
@@ -254,8 +273,8 @@ when logOrc or orcLeakDetector:
 
 proc free(s: Cell; desc: PNimTypeV2) {.inline.} =
   when traceCollector:
-    cprintf("[From ] %p rc %ld color %ld\n", s, s.rc shr rcShift, s.color)
-  if (s.rc and inRootsFlag) == 0:
+    cprintf("[From ] %p rc %ld color %ld\n", s, loadRc(s) shr rcShift, s.color)
+  if (loadRc(s) and inRootsFlag) == 0:
     let p = s +! sizeof(RefHeader)
     when logOrc: writeCell("free", s, desc)
     if desc.destructor != nil:
@@ -288,7 +307,7 @@ proc scanBlack(s: Cell; desc: PNimTypeV2; j: var GcEnv) =
   while j.traceStack.len > until:
     let (entry, desc) = j.traceStack.pop()
     let t = head entry[]
-    t.rc = t.rc +% rcIncrement
+    trialInc(t)
     if t.color != colBlack:
       t.setColor colBlack
       trace(t, desc, j)
@@ -298,23 +317,23 @@ proc markGray(s: Cell; desc: PNimTypeV2; j: var GcEnv) =
   if s.color != colGray:
     s.setColor colGray
     j.touched = j.touched +% 1
-    j.rcSum = j.rcSum +% (s.rc shr rcShift) +% 1
+    j.rcSum = j.rcSum +% (loadRc(s) shr rcShift) +% 1
     orcAssert(j.traceStack.len == 0, "markGray: trace stack not empty")
     trace(s, desc, j)
     while j.traceStack.len > 0:
       let (entry, desc) = j.traceStack.pop()
       let t = head entry[]
-      t.rc = t.rc -% rcIncrement
+      trialDec(t)
       j.edges = j.edges +% 1
       if t.color != colGray:
         t.setColor colGray
         j.touched = j.touched +% 1
-        j.rcSum = j.rcSum +% (t.rc shr rcShift) +% 2
+        j.rcSum = j.rcSum +% (loadRc(t) shr rcShift) +% 2
         trace(t, desc, j)
 
 proc scan(s: Cell; desc: PNimTypeV2; j: var GcEnv) =
   if s.color == colGray:
-    if (s.rc shr rcShift) >= 0:
+    if (loadRc(s) shr rcShift) >= 0:
       scanBlack(s, desc, j)
     else:
       orcAssert(j.traceStack.len == 0, "scan: trace stack not empty")
@@ -324,14 +343,14 @@ proc scan(s: Cell; desc: PNimTypeV2; j: var GcEnv) =
         let (entry, desc) = j.traceStack.pop()
         let t = head entry[]
         if t.color == colGray:
-          if (t.rc shr rcShift) >= 0:
+          if (loadRc(t) shr rcShift) >= 0:
             scanBlack(t, desc, j)
           else:
             t.setColor(colWhite)
             trace(t, desc, j)
 
 proc collectColor(s: Cell; desc: PNimTypeV2; col: int; j: var GcEnv) =
-  if s.color == col and (s.rc and inRootsFlag) == 0:
+  if s.color == col and (loadRc(s) and inRootsFlag) == 0:
     orcAssert(j.traceStack.len == 0, "collectWhite: trace stack not empty")
     s.setColor(colBlack)
     j.toFree.add(s, desc)
@@ -340,89 +359,54 @@ proc collectColor(s: Cell; desc: PNimTypeV2; col: int; j: var GcEnv) =
       let (entry, desc) = j.traceStack.pop()
       let t = head entry[]
       entry[] = nil
-      if t.color == col and (t.rc and inRootsFlag) == 0:
+      if t.color == col and (loadRc(t) and inRootsFlag) == 0:
         j.toFree.add(t, desc)
         t.setColor(colBlack)
         trace(t, desc, j)
 
 proc collectCyclesBacon(j: var GcEnv; lowMark: int) =
+  # YRC defers all destruction to collection time - process ALL roots through Bacon's algorithm
+  # This is different from ORC which handles immediate garbage (rc == 0) directly
+  if lockState == Collecting:
+    return
+  lockState = Collecting
   let last = roots.len -% 1
   when logOrc:
     for i in countdown(last, lowMark):
       writeCell("root", roots.d[i][0], roots.d[i][1])
-  init j.toFree
 
-  # First pass: swap roots with rc <= 0 to the end for immediate freeing
-  # Check RC before markGray modifies it. Use a while loop that shrinks as we iterate.
-  var cycleStart = lowMark
-  var immediateFreeStart = roots.len
-  while cycleStart < immediateFreeStart:
-    let s = roots.d[cycleStart][0]
-    if (s.rc shr rcShift) < 0:
-      # Root is already garbage, swap to end for immediate freeing
-      dec immediateFreeStart
-      swap(roots.d[cycleStart], roots.d[immediateFreeStart])
-      when logOrc: writeCell("root swapped to end for immediate free (rc <= 0)", roots.d[immediateFreeStart][0], roots.d[immediateFreeStart][1])
-    else:
-      inc cycleStart
-
-  # Second pass: process remaining roots (rc > 0) for cycle detection
-  # Only process roots from lowMark to immediateFreeStart (cycleStart == immediateFreeStart after swap loop)
-  for i in lowMark..<immediateFreeStart:
+  # Process all roots through markGray (Bacon's algorithm)
+  for i in countdown(last, lowMark):
     markGray(roots.d[i][0], roots.d[i][1], j)
+
   var colToCollect = colWhite
   if j.rcSum == j.edges:
+    # Short-cut: we know everything is garbage
     colToCollect = colGray
     j.keepThreshold = true
   else:
-    for i in lowMark..<immediateFreeStart:
+    # Normal scan phase
+    for i in countdown(last, lowMark):
       scan(roots.d[i][0], roots.d[i][1], j)
-  for i in lowMark..<immediateFreeStart:
-    let s = roots.d[i][0]
-    s.rc = s.rc and not inRootsFlag
-    collectColor(s, roots.d[i][1], colToCollect, j)
-  when not defined(nimStressOrc):
-    let oldThreshold = rootsThreshold
-    rootsThreshold = high(int)
 
-  # Prepare immediate-free roots for freeing: recursively trace through ALL descendants
-  # and set child pointers to nil, just like collectColor does. This prevents destructors
-  # from accessing children and triggering nested collectCycles().
-  # Add them to j.toFree so they're freed together after roots.len = 0 is set.
-  # Keep inRootsFlag set until right before freeing to prevent mergePendingRoots from
-  # accessing freed cells during nested collectCycles().
-  let immediateFreeCount = roots.len - immediateFreeStart
-  for i in immediateFreeStart..<roots.len:
+  # Collect phase: free all garbage objects
+  init j.toFree
+  for i in 0 ..< roots.len:
     let s = roots.d[i][0]
-    let desc = roots.d[i][1]
-    # Don't clear inRootsFlag yet - keep it set so mergePendingRoots can skip this cell
-    orcAssert(j.traceStack.len == 0, "trace stack not empty before preparing immediate-free root")
-    s.setColor(colBlack)
-    j.toFree.add(s, desc)
-    trace(s, desc, j)
-    # Recursively trace and nil ALL descendants, just like collectColor does
-    # This ensures destructors can't access any children, preventing nested collections
-    while j.traceStack.len > 0:
-      let (entry, childDesc) = j.traceStack.pop()
-      let t = head entry[]
-      entry[] = nil
-      # Recursively trace children to nil their descendants too
-      trace(t, childDesc, j)
+    rcClearFlag(s, inRootsFlag)
+    collectColor(s, roots.d[i][1], colToCollect, j)
 
   # Clear roots before freeing to prevent nested collectCycles() from accessing freed cells
   roots.len = 0
 
-  # Free all roots (both immediate-free and cycle-detected) together
+  # Free all collected objects
   # Destructors must not call nimDecRefIsLastCyclicStatic (add to toDec) during this phase
   for i in 0 ..< j.toFree.len:
     let s = j.toFree.d[i][0]
-    s.rc = s.rc and not inRootsFlag
     when orcLeakDetector:
       writeCell("CYCLIC OBJECT FREED", s, j.toFree.d[i][1])
     free(s, j.toFree.d[i][1])
-  when not defined(nimStressOrc):
-    rootsThreshold = oldThreshold
-  j.freed = j.freed +% j.toFree.len +% immediateFreeCount
+  j.freed = j.freed +% j.toFree.len
   deinit j.toFree
 
 when defined(nimOrcStats):
@@ -431,9 +415,10 @@ when defined(nimOrcStats):
 proc collectCycles() =
   when logOrc:
     cfprintf(cstderr, "[collectCycles] begin\n")
-  withLock gYrcGlobalLock:
+  yrcCollectorLock:
     mergePendingRoots()
-    if roots.len >= RootsThreshold and mayRunCycleCollect():
+    if roots.len >= rootsThreshold and mayRunCycleCollect():
+      let nRoots = roots.len
       var j: GcEnv
       init j.traceStack
       collectCyclesBacon(j, 0)
@@ -450,8 +435,11 @@ proc collectCycles() =
         elif rootsThreshold < high(int) div 4:
           rootsThreshold = (if rootsThreshold <= 0: defaultThreshold else: rootsThreshold)
           rootsThreshold = rootsThreshold div 2 +% rootsThreshold
-          # Cap growth so threshold doesn't grow without bound when we rarely free cycles
-          #rootsThreshold = min(rootsThreshold, defaultThreshold *% 16)
+          # Cost-aware: if this run was expensive (large graph), raise threshold more so we don't run again too soon
+          if j.touched > nRoots *% 4:
+            rootsThreshold = rootsThreshold div 2 +% rootsThreshold
+          rootsThreshold = min(rootsThreshold, defaultThreshold *% 16)
+          rootsThreshold = min(rootsThreshold, nRoots *% 2)
       when logOrc:
         cfprintf(cstderr, "[collectCycles] end; freed %ld new threshold %ld\n", j.freed, rootsThreshold)
       when defined(nimOrcStats):
@@ -466,9 +454,9 @@ when defined(nimOrcStats):
     result = OrcStats(freedCyclicObjects: freedCyclicObjects)
 
 proc GC_runOrc* =
-  withLock gYrcGlobalLock:
+  yrcCollectorLock:
     mergePendingRoots()
-    if mayRunCycleCollect():
+    if roots.len > 0 and mayRunCycleCollect():
       var j: GcEnv
       init j.traceStack
       collectCyclesBacon(j, 0)
@@ -485,12 +473,12 @@ proc GC_disableOrc*() =
     rootsThreshold = high(int)
 
 proc GC_prepareOrc*(): int {.inline.} =
-  withLock gYrcGlobalLock:
+  yrcCollectorLock:
     mergePendingRoots()
     result = roots.len
 
 proc GC_partialCollect*(limit: int) =
-  withLock gYrcGlobalLock:
+  yrcCollectorLock:
     mergePendingRoots()
     if roots.len > limit and mayRunCycleCollect():
       var j: GcEnv
@@ -566,22 +554,24 @@ proc yrcDec(tmp: pointer; desc: PNimTypeV2) {.inline.} =
 
 proc nimAsgnYrc(dest: ptr pointer; src: pointer; desc: PNimTypeV2) {.compilerRtl.} =
   ## YRC write barrier for ref copy assignment.
-  ## Atomically stores src into dest, then buffers RC adjustments.
-  ## Freeing is always done by the cycle collector, never inline.
+  ## Holds the mutator read lock for the entire operation so the collector
+  ## cannot run between the incRef and decRef, closing the stale-decRef
+  ## bug. Direct atomic incRef replaces the toInc stripe queue: the
+  ## collector is blocked, so the RC update is immediately visible and correct.
+  acquireMutatorLock()
+  if src != nil: increment head(src)   # direct atomic: no toInc queue needed
   let tmp = dest[]
-  atomicStoreN(dest, src, ATOMIC_RELEASE)
-  if src != nil:
-    nimIncRefCyclic(src, true)
-  if tmp != nil:
-    yrcDec(tmp, desc)
+  dest[] = src
+  if tmp != nil: yrcDec(tmp, desc)     # still deferred via toDec for cycle detection
+  releaseMutatorLock()
 
 proc nimSinkYrc(dest: ptr pointer; src: pointer; desc: PNimTypeV2) {.compilerRtl.} =
   ## YRC write barrier for ref sink (move). No incRef on source.
-  ## Freeing is always done by the cycle collector, never inline.
+  acquireMutatorLock()
   let tmp = dest[]
-  atomicStoreN(dest, src, ATOMIC_RELEASE)
-  if tmp != nil:
-    yrcDec(tmp, desc)
+  dest[] = src
+  if tmp != nil: yrcDec(tmp, desc)
+  releaseMutatorLock()
 
 proc nimMarkCyclic(p: pointer) {.compilerRtl, inl.} =
   when optimizedOrc:
@@ -589,10 +579,12 @@ proc nimMarkCyclic(p: pointer) {.compilerRtl, inl.} =
       let h = head(p)
       h.rc = h.rc or maybeCycle
 
-# Initialize locks at module load
-initLock(gYrcGlobalLock)
+# Initialize locks at module load.
+# RwLock stripes live in seqs_v2 (gYrcLocks); NumLockStripes is exported from there.
+for i in 0..<NumLockStripes:
+  initRwLock(gYrcLocks[i].lock)
 for i in 0..<NumStripes:
-  when not defined(yrcAtomics):
+  when not defined(yrcAtomics) and not defined(nimYrcAtomicIncs):
     initLock(stripes[i].lockInc)
   initLock(stripes[i].lockDec)
 

lib/system/yrc_proof.tla

@@ -42,6 +42,32 @@
 \*   - Mutator must hold stack ref to modify object (external ref)
 \*   - scanBlack follows current physical edges (rescues newly written objects)
 \*   - Only objects unreachable from any stack root are freed
+\*
+\* ## Seq Payload Race and RWLock Fix
+\*
+\* Value types like seq[T] (where T can form cycles) have internal heap
+\* allocations (data arrays / "payloads") that are freed by value-type
+\* hooks (=sink, =destroy), NOT by the cycle collector. This creates a race:
+\*
+\*   1. Object O has a seq field with payload P containing refs
+\*   2. Collector starts tracing O -- reads payload pointer P
+\*   3. Mutator does O.seq = newSeq -- frees P (value-type destructor)
+\*   4. Collector dereferences P -- use-after-free!
+\*
+\* Fix: Change the global YRC lock to a read-write lock (RWLock).
+\*   - Collector acquires the WRITE lock (exclusive access during tracing)
+\*   - Seq mutations (assign, setLen, add, etc.) acquire the READ lock
+\*   - Multiple seq mutations can proceed concurrently (read lock is shared)
+\*   - But seq mutations block while the collector traces (write lock is exclusive)
+\*
+\* This prevents the race: the mutator cannot free a payload while the
+\* collector is tracing it, because acquiring the read lock requires
+\* the write lock to be unheld.
+\*
+\* Deadlock avoidance: If a seq operation triggers collectCycles() via stripe
+\* overflow while already holding the read lock, it must NOT attempt to
+\* acquire the write lock. Instead, it should drain the overflow buffers
+\* without running the full collection cycle.
 
 EXTENDS Naturals, Integers, Sequences, FiniteSets, TLC
 
@@ -53,10 +79,14 @@ ASSUME IsFiniteSet(Objects)
 ASSUME IsFiniteSet(Threads)
 ASSUME IsFiniteSet(ObjTypes)
 
+\* Seq payload identifiers (models heap-allocated data arrays of seq[T])
+CONSTANTS SeqPayloads
+ASSUME IsFiniteSet(SeqPayloads)
+
 \* NULL constant (represents "no thread" for locks)
 \* We use a sentinel value that's guaranteed not to be in Threads or Objects
 NULL == "NULL"  \* String literal that won't conflict with Threads/Objects
-ASSUME NULL \notin Threads /\ NULL \notin Objects
+ASSUME NULL \notin Threads /\ NULL \notin Objects /\ NULL \notin SeqPayloads
 
 \* Helper functions
 \* Note: GetStripeIdx is not used, GetStripe is used instead
@@ -90,15 +120,29 @@ VARIABLES
     \* Per-stripe locks
     lockInc,            \* lockInc[stripe] = thread holding increment lock (or NULL)
     lockDec,            \* lockDec[stripe] = thread holding decrement lock (or NULL)
-    \* Global lock
-    globalLock,         \* thread holding global lock (or NULL)
+    \* Global lock (now the WRITE side of the RWLock)
+    globalLock,         \* thread holding write lock (or NULL)
     \* Merged roots array (used during collection)
     mergedRoots,        \* sequence of (object, type) pairs
     \* Collection state
     collecting,         \* TRUE if collection is in progress
     gcEnv,              \* GC environment: {touched, edges, rcSum, toFree, ...}
     \* Pending operations (for modeling atomicity)
-    pendingWrites       \* set of pending write barrier operations
+    pendingWrites,      \* set of pending write barrier operations
+    \* --- Seq payload race modeling ---
+    \* Seq payloads: models the heap-allocated data arrays of seq[T] fields
+    seqData,            \* [Objects -> SeqPayloads \cup {NULL}] -- current payload for obj's seq
+    payloadAlive,       \* [SeqPayloads -> BOOLEAN] -- is this payload's memory valid?
+    \* RWLock read side: set of threads holding the read lock.
+    \* Seq mutations (assign, add, setLen, etc.) acquire the read lock.
+    \* The collector (write lock holder) gets exclusive access.
+    rwLockReaders,      \* SUBSET Threads -- threads currently holding the read lock
+    \* Collector's in-progress seq trace: the payload pointer read during tracing.
+    \* Between reading the pointer and accessing the data, the payload could be freed.
+    collectorPayload    \* SeqPayloads \cup {NULL} -- payload being traced by collector
+
+\* Convenience tuple for seq-related variables (used in UNCHANGED clauses)
+seqVars == <<seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 \* Type invariants
 TypeOK ==
@@ -117,6 +161,11 @@ TypeOK ==
     /\ mergedRoots \in Seq([obj: Objects, desc: ObjTypes])
     /\ collecting \in BOOLEAN
     /\ pendingWrites \in SUBSET ([thread: Threads, dest: Objects, old: Objects \cup {NULL}, src: Objects \cup {NULL}, phase: {"store", "inc", "dec"}])
+    \* Seq payload types
+    /\ seqData \in [Objects -> SeqPayloads \cup {NULL}]
+    /\ payloadAlive \in [SeqPayloads -> BOOLEAN]
+    /\ rwLockReaders \in SUBSET Threads
+    /\ collectorPayload \in SeqPayloads \cup {NULL}
 
 \* Helper: internal reference count (heap-to-heap edges)
 InternalRC(obj) ==
@@ -163,7 +212,7 @@ MutatorWriteAtomicStore(thread, destObj, destField, oldVal, newVal, desc) ==
                                                  IF x = newVal /\ newVal # NULL
                                                  THEN TRUE
                                                  ELSE FALSE]]
-    /\ UNCHANGED <<roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites>>
+    /\ UNCHANGED <<roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 \* ============================================================================
 \* Phase 2: RC Buffering (if space available)
@@ -193,7 +242,7 @@ WriteBarrier(thread, destObj, destField, oldVal, newVal, desc) ==
        /\ toDec' = IF oldVal # NULL /\ toDecLen[stripe] < QueueSize
                    THEN [toDec EXCEPT ![stripe] = Append(toDec[stripe], [obj |-> oldVal, desc |-> desc])]
                    ELSE toDec
-       /\ UNCHANGED <<edges, roots, rc, color, inRoots, mergedRoots, lockInc, lockDec, globalLock, collecting, gcEnv, pendingWrites>>
+       /\ UNCHANGED <<edges, roots, rc, color, inRoots, mergedRoots, lockInc, lockDec, globalLock, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 \* ============================================================================
 \* Phase 3: Overflow Handling (separate actions that can block)
@@ -215,7 +264,7 @@ MutatorWriteMergeInc(thread) ==
                   externalRC == Cardinality({t \in Threads : roots[t][x]})
               IN internalRC + externalRC]
     /\ globalLock' = NULL  \* Release lock after merge
-    /\ UNCHANGED <<edges, roots, color, inRoots, toDecLen, toDec, lockInc, lockDec, mergedRoots, collecting, gcEnv, pendingWrites>>
+    /\ UNCHANGED <<edges, roots, color, inRoots, toDecLen, toDec, lockInc, lockDec, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 \* Handle decrement overflow: merge ALL buffers when lock is available
 \* This calls collectCycles() which merges both increment and decrement buffers
@@ -257,7 +306,7 @@ MutatorWriteMergeDec(thread) ==
        /\ toDecLen' = [s \in 0..(NumStripes-1) |-> 0]
        /\ toDec' = [s \in 0..(NumStripes-1) |-> <<>>]
     /\ globalLock' = NULL  \* Lock acquired, merge done, lock released (entire withLock block is atomic)
-    /\ UNCHANGED <<edges, roots, color, lockInc, lockDec, collecting, gcEnv, pendingWrites>>
+    /\ UNCHANGED <<edges, roots, color, lockInc, lockDec, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 \* ============================================================================
 \* Merge Operation: mergePendingRoots
@@ -311,7 +360,7 @@ MergePendingRoots ==
        /\ toInc' = [s \in 0..(NumStripes-1) |-> <<>>]
        /\ toDecLen' = [s \in 0..(NumStripes-1) |-> 0]
        /\ toDec' = [s \in 0..(NumStripes-1) |-> <<>>]
-    /\ UNCHANGED <<edges, roots, color, lockInc, lockDec, globalLock, collecting, gcEnv, pendingWrites>>
+    /\ UNCHANGED <<edges, roots, color, lockInc, lockDec, globalLock, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 \* ============================================================================
 \* Trial Deletion: markGray
@@ -365,7 +414,7 @@ MarkGray(obj, desc) ==
           \* For roots, the RC includes external refs which survive trial deletion.
           rc' = [x \in Objects |->
               IF x \in allReachable THEN rc[x] - internalEdgeCount[x] ELSE rc[x]]
-    /\ UNCHANGED <<edges, roots, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites>>
+    /\ UNCHANGED <<edges, roots, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 \* ============================================================================
 \* Scan Phase
@@ -422,7 +471,7 @@ Scan(obj, desc) ==
        ELSE \* Mark white (part of closed cycle)
             /\ color' = [color EXCEPT ![obj] = colWhite]
             /\ UNCHANGED <<rc>>
-    /\ UNCHANGED <<edges, roots, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites>>
+    /\ UNCHANGED <<edges, roots, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 \* ============================================================================
 \* Collection Phase: collectColor
@@ -442,7 +491,7 @@ CollectColor(obj, desc, targetColor) ==
        edges' = [edges EXCEPT ![obj] = [x \in Objects |->
            IF x = obj THEN FALSE ELSE edges[obj][x]]]
     /\ color' = [color EXCEPT ![obj] = colBlack]  \* Mark as freed
-    /\ UNCHANGED <<roots, rc, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites>>
+    /\ UNCHANGED <<roots, rc, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 \* ============================================================================
 \* Collection Cycle: collectCyclesBacon
@@ -454,7 +503,7 @@ StartCollection ==
     /\ Len(mergedRoots) >= RootsThreshold
     /\ collecting' = TRUE
     /\ gcEnv' = [touched |-> 0, edges |-> 0, rcSum |-> 0, toFree |-> {}]
-    /\ UNCHANGED <<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, pendingWrites>>
+    /\ UNCHANGED <<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 EndCollection ==
     /\ globalLock # NULL
@@ -464,7 +513,7 @@ EndCollection ==
            IF x \in {r.obj : r \in mergedRoots} THEN FALSE ELSE inRoots[x]]
     /\ mergedRoots' = <<>>
     /\ collecting' = FALSE
-    /\ UNCHANGED <<edges, roots, rc, color, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, gcEnv, pendingWrites>>
+    /\ UNCHANGED <<edges, roots, rc, color, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 \* ============================================================================
 \* Mutator Actions
@@ -491,7 +540,7 @@ MutatorWrite(thread, destObj, destField, oldVal, newVal, desc) ==
        IF incOverflow \/ decOverflow
        THEN \* Overflow: atomic store happened, but buffering is deferred
             \* Buffers stay full, merge will happen when lock is available (via MutatorWriteMergeInc/Dec)
-            /\ UNCHANGED <<roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites>>
+            /\ UNCHANGED <<roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
        ELSE \* No overflow: buffer normally
             /\ WriteBarrier(thread, destObj, destField, oldVal, newVal, desc)
             /\ UNCHANGED <<roots, collecting, pendingWrites>>
@@ -521,16 +570,19 @@ MutatorRootAssign(thread, obj, val) ==
     /\ collecting' = collecting
     /\ gcEnv' = gcEnv
     /\ pendingWrites' = pendingWrites
+    /\ UNCHANGED seqVars
 
 \* ============================================================================
 \* Collector Actions
 \* ============================================================================
 
-\* Collector acquires global lock for entire collection cycle
+\* Collector acquires write lock (global lock) for entire collection cycle.
+\* RWLock semantics: writer can only acquire when no readers hold the read lock.
 CollectorAcquireLock(thread) ==
     /\ globalLock = NULL
+    /\ rwLockReaders = {}   \* RWLock: no readers allowed when acquiring write lock
     /\ globalLock' = thread
-    /\ UNCHANGED <<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, mergedRoots, collecting, gcEnv, pendingWrites>>
+    /\ UNCHANGED <<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 CollectorMerge ==
     /\ globalLock # NULL
@@ -571,7 +623,93 @@ CollectorEnd ==
 CollectorReleaseLock(thread) ==
     /\ globalLock = thread
     /\ globalLock' = NULL
-    /\ UNCHANGED <<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, mergedRoots, collecting, gcEnv, pendingWrites>>
+    /\ UNCHANGED <<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
+
+\* ============================================================================
+\* Seq Payload Actions (RWLock-protected)
+\* ============================================================================
+\* These actions model the race between the collector tracing seq payloads
+\* and mutators replacing/freeing seq payloads.
+\*
+\* The collector traces seq payloads in two steps:
+\*   1. CollectorStartTraceSeq: reads seqData[obj] (gets payload pointer)
+\*   2. CollectorFinishTraceSeq: accesses the payload data
+\* Between these steps, a mutator could free the payload (the race).
+\*
+\* The RWLock prevents this:
+\*   - Collector holds write lock (globalLock) during tracing
+\*   - MutatorSeqAssign requires read lock (rwLockReaders)
+\*   - Read lock requires globalLock = NULL
+\*   - Therefore MutatorSeqAssign is blocked during collection
+\*
+\* Note: This models the memory safety aspect of seq tracing.
+\* The cycle collection algorithm (MarkGray, Scan, etc.) operates on the
+\* logical edge graph. Seq payloads are a physical representation detail
+\* that affects memory safety but not GC correctness (which is already
+\* covered by the existing Safety property).
+
+\* Mutator acquires read lock for seq mutation.
+\* RWLock semantics: read lock can be acquired when no writer holds the write lock.
+\* Multiple readers can hold the read lock simultaneously.
+MutatorAcquireSeqLock(thread) ==
+    /\ globalLock = NULL          \* RWLock: no writer allowed when acquiring read lock
+    /\ thread \notin rwLockReaders
+    /\ rwLockReaders' = rwLockReaders \cup {thread}
+    /\ UNCHANGED <<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, collectorPayload>>
+
+\* Mutator releases read lock after seq mutation completes.
+MutatorReleaseSeqLock(thread) ==
+    /\ thread \in rwLockReaders
+    /\ rwLockReaders' = rwLockReaders \ {thread}
+    /\ UNCHANGED <<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, collectorPayload>>
+
+\* Mutator replaces a seq field's payload (e.g., r.list = newSeq).
+\* This frees the old payload and installs a new one.
+\* Requires the read lock (RWLock protection against concurrent collection).
+\*
+\* In the real implementation, this is a value-type assignment (=sink/=copy)
+\* that frees the old data array and installs a new one. The old array is freed
+\* immediately, NOT deferred to the cycle collector.
+MutatorSeqAssign(thread, obj, newPayload) ==
+    /\ thread \in rwLockReaders     \* Must hold read lock
+    /\ seqData[obj] # NULL          \* Object has an existing seq payload
+    /\ newPayload \in SeqPayloads
+    /\ ~payloadAlive[newPayload]     \* New payload is freshly allocated (not yet alive)
+    /\ LET oldPayload == seqData[obj]
+       IN
+       /\ seqData' = [seqData EXCEPT ![obj] = newPayload]
+       /\ payloadAlive' = [payloadAlive EXCEPT ![oldPayload] = FALSE,
+                                               ![newPayload] = TRUE]
+    \* Note: In a complete model, this would also update edges[obj] to reflect
+    \* the new seq elements and buffer RC changes (inc new elements, dec old elements).
+    \* We omit this here to focus on the memory safety property (payload lifetime).
+    /\ UNCHANGED <<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites, rwLockReaders, collectorPayload>>
+
+\* Collector begins tracing an object's seq field.
+\* Reads the seqData pointer and stores it in collectorPayload.
+\* This is the first step of a two-step trace operation.
+\* The collector must hold the write lock (globalLock).
+CollectorStartTraceSeq(obj) ==
+    /\ globalLock # NULL             \* Collector holds write lock
+    /\ collecting = TRUE             \* In collection phase
+    /\ seqData[obj] # NULL           \* Object has a seq field
+    /\ collectorPayload = NULL       \* Not already mid-trace
+    /\ collectorPayload' = seqData[obj]
+    /\ UNCHANGED <<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders>>
+
+\* Collector finishes tracing an object's seq field.
+\* Accesses the payload data via collectorPayload.
+\* The payload MUST still be alive (this is checked by SeqPayloadSafety).
+\* After accessing the payload, clears collectorPayload.
+CollectorFinishTraceSeq ==
+    /\ globalLock # NULL             \* Collector holds write lock
+    /\ collecting = TRUE             \* In collection phase
+    /\ collectorPayload # NULL       \* Mid-trace on a payload
+    \* The actual work: read payloadEdges[collectorPayload] to discover children.
+    \* We don't model the trace results here; the safety property ensures
+    \* the read is valid (payload is alive).
+    /\ collectorPayload' = NULL
+    /\ UNCHANGED <<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders>>
 
 \* ============================================================================
 \* Next State Relation
@@ -607,6 +745,16 @@ Next ==
     \/ CollectorEnd
     \/ \E thread \in Threads:
          CollectorReleaseLock(thread)
+    \* --- Seq payload actions ---
+    \/ \E thread \in Threads:
+         MutatorAcquireSeqLock(thread)
+    \/ \E thread \in Threads:
+         MutatorReleaseSeqLock(thread)
+    \/ \E thread \in Threads, obj \in Objects, p \in SeqPayloads:
+         MutatorSeqAssign(thread, obj, p)
+    \/ \E obj \in Objects:
+         CollectorStartTraceSeq(obj)
+    \/ CollectorFinishTraceSeq
 
 \* ============================================================================
 \* Initial State
@@ -642,6 +790,11 @@ Init ==
     /\ collecting = FALSE
     /\ gcEnv = [touched |-> 0, edges |-> 0, rcSum |-> 0, toFree |-> {}]
     /\ pendingWrites = {}
+    \* Seq payload initial state
+    /\ seqData = [x \in Objects |-> NULL]        \* No seq fields initially
+    /\ payloadAlive = [p \in SeqPayloads |-> FALSE]  \* No payloads alive initially
+    /\ rwLockReaders = {}                         \* No threads hold read lock
+    /\ collectorPayload = NULL                    \* Collector not mid-trace
     /\ TypeOK
 
 \* ============================================================================
@@ -748,14 +901,53 @@ CycleInvariant ==
         THEN ExternalRC(obj) = 0
         ELSE TRUE
 
+\* ============================================================================
+\* Seq Payload Safety
+\* ============================================================================
+\* Memory safety: The collector never accesses a freed seq payload.
+\*
+\* collectorPayload holds the payload pointer the collector read during
+\* CollectorStartTraceSeq. Between that action and CollectorFinishTraceSeq,
+\* the collector will dereference this pointer to read the seq's elements.
+\* If the payload has been freed in between, this is a use-after-free.
+\*
+\* The RWLock prevents this:
+\*   - collectorPayload is only set when globalLock # NULL (write lock held)
+\*   - MutatorSeqAssign (which frees payloads) requires rwLockReaders membership
+\*   - MutatorAcquireSeqLock requires globalLock = NULL (no writer)
+\*   - Therefore: while collectorPayload # NULL, no MutatorSeqAssign can execute
+\*   - Therefore: payloadAlive[collectorPayload] remains TRUE
+\*
+\* Without the RWLock (if MutatorSeqAssign didn't require the read lock),
+\* the following interleaving would violate this property:
+\*   1. Collector acquires write lock
+\*   2. CollectorStartTraceSeq(obj) -- collectorPayload = P
+\*   3. MutatorSeqAssign(thread, obj, Q) -- frees P, payloadAlive[P] = FALSE
+\*   4. SeqPayloadSafety VIOLATED: collectorPayload = P but payloadAlive[P] = FALSE
+
+SeqPayloadSafety ==
+    collectorPayload # NULL => payloadAlive[collectorPayload]
+
+\* ============================================================================
+\* RWLock Invariant
+\* ============================================================================
+\* The read-write lock ensures mutual exclusion between the collector (writer)
+\* and seq mutations (readers). The writer and readers are never active at
+\* the same time.
+
+RWLockInvariant ==
+    globalLock # NULL => rwLockReaders = {}
+
 \* ============================================================================
 \* Specification
 \* ============================================================================
 
-Spec == Init /\ [][Next]_<<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites>>
+Spec == Init /\ [][Next]_<<edges, roots, rc, color, inRoots, toIncLen, toInc, toDecLen, toDec, lockInc, lockDec, globalLock, mergedRoots, collecting, gcEnv, pendingWrites, seqData, payloadAlive, rwLockReaders, collectorPayload>>
 
 THEOREM Spec => []Safety
 THEOREM Spec => []RCInvariant
 THEOREM Spec => []CycleInvariant
+THEOREM Spec => []SeqPayloadSafety
+THEOREM Spec => []RWLockInvariant
 
 ====

nimdoc/extlinks/project/expected/main.html

@@ -99,7 +99,7 @@
   <h1><a class="toc-backref" href="#7">Types</a></h1>
   <dl class="item">
     <div id="A">
-  <dt><pre><a href="main.html#A"><span class="Identifier">A</span></a> <span class="Other">=</span> <span class="Keyword">object</span></pre></dt>
+  <dt><pre><a href="#A"><span class="Identifier">A</span></a> <span class="Other">=</span> <span class="Keyword">object</span></pre></dt>
   <dd>
     
     

nimdoc/extlinks/project/expected/sub/submodule.html

@@ -88,7 +88,7 @@
   <h1><a class="toc-backref" href="#7">Types</a></h1>
   <dl class="item">
     <div id="submoduleInt">
-  <dt><pre><a href="submodule.html#submoduleInt"><span class="Identifier">submoduleInt</span></a> <span class="Other">=</span> <span class="Keyword">distinct</span> <span class="Identifier">int</span></pre></dt>
+  <dt><pre><a href="#submoduleInt"><span class="Identifier">submoduleInt</span></a> <span class="Other">=</span> <span class="Keyword">distinct</span> <span class="Identifier">int</span></pre></dt>
   <dd>
     
     

nimdoc/testproject/expected/nimdoc.out.css

@@ -123,7 +123,6 @@ Modified by Boyd Greenfield and narimiran
 }
 
 html {
-  overflow-x: hidden;
   max-width: 100%;
   box-sizing: border-box;
   font-size: 100%;
@@ -572,8 +571,8 @@ blockquote.markdown-quote {
   padding-left: 3px;
   padding-right: 3px;
   border-radius: 4px;
-  white-space: normal;
-  word-break: break-all;
+  white-space: pre-wrap;
+  overflow-wrap: break-word;
 }
 
 span.tok {
@@ -674,6 +673,8 @@ table {
   border-collapse: collapse;
   border-color: var(--third-background);
   border-spacing: 0;
+  display: block;
+  overflow-x: auto;
 }
 
 table:not(.line-nums-table) {

nimdoc/testproject/expected/subdir/subdir_b/utils.html

@@ -257,7 +257,7 @@ Ref. <a class="reference internal nimdoc" title="proc `[]`[T](x: G[T]): T" href=
   <h1><a class="toc-backref" href="#7">Types</a></h1>
   <dl class="item">
     <div id="G">
-  <dt><pre><a href="utils.html#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span> <span class="Other">=</span> <span class="Keyword">object</span></pre></dt>
+  <dt><pre><a href="#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span> <span class="Other">=</span> <span class="Keyword">object</span></pre></dt>
   <dd>
     
     
@@ -265,7 +265,7 @@ Ref. <a class="reference internal nimdoc" title="proc `[]`[T](x: G[T]): T" href=
   </dd>
 </div>
 <div id="SomeType">
-  <dt><pre><a href="utils.html#SomeType"><span class="Identifier">SomeType</span></a> <span class="Other">=</span> <span class="Keyword">enum</span>
+  <dt><pre><a href="#SomeType"><span class="Identifier">SomeType</span></a> <span class="Other">=</span> <span class="Keyword">enum</span>
   <span class="Identifier">enumValueA</span><span class="Other">,</span> <span class="Identifier">enumValueB</span><span class="Other">,</span> <span class="Identifier">enumValueC</span></pre></dt>
   <dd>
     
@@ -281,7 +281,7 @@ Ref. <a class="reference internal nimdoc" title="proc `[]`[T](x: G[T]): T" href=
   <dl class="item">
     <div id="$-procs-all">
   <div id="$,G[T]">
-  <dt><pre><span class="Keyword">proc</span> <a href="#%24%2CG%5BT%5D"><span class="Identifier">`$`</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">(</span><span class="Identifier">a</span><span class="Other">:</span> <a href="utils.html#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">)</span><span class="Other">:</span> <span class="Identifier">string</span></pre></dt>
+  <dt><pre><span class="Keyword">proc</span> <a href="#%24%2CG%5BT%5D"><span class="Identifier">`$`</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">(</span><span class="Identifier">a</span><span class="Other">:</span> <a href="#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">)</span><span class="Other">:</span> <span class="Identifier">string</span></pre></dt>
   <dd>
     
     
@@ -289,7 +289,7 @@ Ref. <a class="reference internal nimdoc" title="proc `[]`[T](x: G[T]): T" href=
   </dd>
 </div>
 <div id="$,ref.SomeType">
-  <dt><pre><span class="Keyword">proc</span> <a href="#%24%2Cref.SomeType"><span class="Identifier">`$`</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">(</span><span class="Identifier">a</span><span class="Other">:</span> <span class="Keyword">ref</span> <a href="utils.html#SomeType"><span class="Identifier">SomeType</span></a><span class="Other">)</span><span class="Other">:</span> <span class="Identifier">string</span></pre></dt>
+  <dt><pre><span class="Keyword">proc</span> <a href="#%24%2Cref.SomeType"><span class="Identifier">`$`</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">(</span><span class="Identifier">a</span><span class="Other">:</span> <span class="Keyword">ref</span> <a href="#SomeType"><span class="Identifier">SomeType</span></a><span class="Other">)</span><span class="Other">:</span> <span class="Identifier">string</span></pre></dt>
   <dd>
     
     
@@ -300,7 +300,7 @@ Ref. <a class="reference internal nimdoc" title="proc `[]`[T](x: G[T]): T" href=
 </div>
 <div id="'big-procs-all">
   <div id="'big,string">
-  <dt><pre><span class="Keyword">func</span> <a href="#%27big%2Cstring"><span class="Identifier">`'big`</span></a><span class="Other">(</span><span class="Identifier">a</span><span class="Other">:</span> <span class="Identifier">string</span><span class="Other">)</span><span class="Other">:</span> <a href="utils.html#SomeType"><span class="Identifier">SomeType</span></a> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
+  <dt><pre><span class="Keyword">func</span> <a href="#%27big%2Cstring"><span class="Identifier">`'big`</span></a><span class="Other">(</span><span class="Identifier">a</span><span class="Other">:</span> <span class="Identifier">string</span><span class="Other">)</span><span class="Other">:</span> <a href="#SomeType"><span class="Identifier">SomeType</span></a> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
   <dd>
     
     
@@ -311,7 +311,7 @@ Ref. <a class="reference internal nimdoc" title="proc `[]`[T](x: G[T]): T" href=
 </div>
 <div id="[]-procs-all">
   <div id="[],G[T]">
-  <dt><pre><span class="Keyword">proc</span> <a href="#%5B%5D%2CG%5BT%5D"><span class="Identifier">`[]`</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">(</span><span class="Identifier">x</span><span class="Other">:</span> <a href="utils.html#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">)</span><span class="Other">:</span> <span class="Identifier">T</span></pre></dt>
+  <dt><pre><span class="Keyword">proc</span> <a href="#%5B%5D%2CG%5BT%5D"><span class="Identifier">`[]`</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">(</span><span class="Identifier">x</span><span class="Other">:</span> <a href="#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">)</span><span class="Other">:</span> <span class="Identifier">T</span></pre></dt>
   <dd>
     
     
@@ -322,7 +322,7 @@ Ref. <a class="reference internal nimdoc" title="proc `[]`[T](x: G[T]): T" href=
 </div>
 <div id="[]=-procs-all">
   <div id="[]=,G[T],int,T">
-  <dt><pre><span class="Keyword">proc</span> <a href="#%5B%5D%3D%2CG%5BT%5D%2Cint%2CT"><span class="Identifier">`[]=`</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">(</span><span class="Identifier">a</span><span class="Other">:</span> <span class="Keyword">var</span> <a href="utils.html#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">;</span> <span class="Identifier">index</span><span class="Other">:</span> <span class="Identifier">int</span><span class="Other">;</span> <span class="Identifier">value</span><span class="Other">:</span> <span class="Identifier">T</span><span class="Other">)</span></pre></dt>
+  <dt><pre><span class="Keyword">proc</span> <a href="#%5B%5D%3D%2CG%5BT%5D%2Cint%2CT"><span class="Identifier">`[]=`</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">(</span><span class="Identifier">a</span><span class="Other">:</span> <span class="Keyword">var</span> <a href="#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">T</span><span class="Other">]</span><span class="Other">;</span> <span class="Identifier">index</span><span class="Other">:</span> <span class="Identifier">int</span><span class="Other">;</span> <span class="Identifier">value</span><span class="Other">:</span> <span class="Identifier">T</span><span class="Other">)</span></pre></dt>
   <dd>
     
     
@@ -345,7 +345,7 @@ Ref. <a class="reference internal nimdoc" title="proc `[]`[T](x: G[T]): T" href=
 </div>
 <div id="f-procs-all">
   <div id="f,G[int]">
-  <dt><pre><span class="Keyword">proc</span> <a href="#f%2CG%5Bint%5D"><span class="Identifier">f</span></a><span class="Other">(</span><span class="Identifier">x</span><span class="Other">:</span> <a href="utils.html#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">int</span><span class="Other">]</span><span class="Other">)</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
+  <dt><pre><span class="Keyword">proc</span> <a href="#f%2CG%5Bint%5D"><span class="Identifier">f</span></a><span class="Other">(</span><span class="Identifier">x</span><span class="Other">:</span> <a href="#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">int</span><span class="Other">]</span><span class="Other">)</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
   <dd>
     
     There is also variant <a class="reference internal nimdoc" title="proc f(x: G[string])" href="#f,G[string]">f(G[string])</a>
@@ -353,7 +353,7 @@ Ref. <a class="reference internal nimdoc" title="proc `[]`[T](x: G[T]): T" href=
   </dd>
 </div>
 <div id="f,G[string]">
-  <dt><pre><span class="Keyword">proc</span> <a href="#f%2CG%5Bstring%5D"><span class="Identifier">f</span></a><span class="Other">(</span><span class="Identifier">x</span><span class="Other">:</span> <a href="utils.html#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">string</span><span class="Other">]</span><span class="Other">)</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
+  <dt><pre><span class="Keyword">proc</span> <a href="#f%2CG%5Bstring%5D"><span class="Identifier">f</span></a><span class="Other">(</span><span class="Identifier">x</span><span class="Other">:</span> <a href="#G"><span class="Identifier">G</span></a><span class="Other">[</span><span class="Identifier">string</span><span class="Other">]</span><span class="Other">)</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
   <dd>
     
     See also <a class="reference internal nimdoc" title="proc f(x: G[int])" href="#f,G[int]">f(G[int])</a>.
@@ -528,7 +528,7 @@ Ref. <a class="reference internal nimdoc" title="proc `[]`[T](x: G[T]): T" href=
 </div>
 <div id="someType-procs-all">
   <div id="someType_2">
-  <dt><pre><span class="Keyword">proc</span> <a href="#someType_2"><span class="Identifier">someType</span></a><span class="Other">(</span><span class="Other">)</span><span class="Other">:</span> <a href="utils.html#SomeType"><span class="Identifier">SomeType</span></a> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
+  <dt><pre><span class="Keyword">proc</span> <a href="#someType_2"><span class="Identifier">someType</span></a><span class="Other">(</span><span class="Other">)</span><span class="Other">:</span> <a href="#SomeType"><span class="Identifier">SomeType</span></a> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
   <dd>
     
     constructor.
@@ -545,7 +545,7 @@ Ref. <a class="reference internal nimdoc" title="proc `[]`[T](x: G[T]): T" href=
   <dl class="item">
     <div id="fooBar-iterators-all">
   <div id="fooBar.i,seq[SomeType]">
-  <dt><pre><span class="Keyword">iterator</span> <a href="#fooBar.i%2Cseq%5BSomeType%5D"><span class="Identifier">fooBar</span></a><span class="Other">(</span><span class="Identifier">a</span><span class="Other">:</span> <span class="Identifier">seq</span><span class="Other">[</span><a href="utils.html#SomeType"><span class="Identifier">SomeType</span></a><span class="Other">]</span><span class="Other">)</span><span class="Other">:</span> <span class="Identifier">int</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
+  <dt><pre><span class="Keyword">iterator</span> <a href="#fooBar.i%2Cseq%5BSomeType%5D"><span class="Identifier">fooBar</span></a><span class="Other">(</span><span class="Identifier">a</span><span class="Other">:</span> <span class="Identifier">seq</span><span class="Other">[</span><a href="#SomeType"><span class="Identifier">SomeType</span></a><span class="Other">]</span><span class="Other">)</span><span class="Other">:</span> <span class="Identifier">int</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
   <dd>
     
     

nimdoc/testproject/expected/testproject.html

@@ -381,7 +381,7 @@
   <h1><a class="toc-backref" href="#7">Types</a></h1>
   <dl class="item">
     <div id="A">
-  <dt><pre><a href="testproject.html#A"><span class="Identifier">A</span></a> {.<span class="Identifier">inject</span>.} <span class="Other">=</span> <span class="Keyword">enum</span>
+  <dt><pre><a href="#A"><span class="Identifier">A</span></a> {.<span class="Identifier">inject</span>.} <span class="Other">=</span> <span class="Keyword">enum</span>
   <span class="Identifier">aA</span></pre></dt>
   <dd>
     
@@ -390,7 +390,7 @@
   </dd>
 </div>
 <div id="AnotherObject">
-  <dt><pre><a href="testproject.html#AnotherObject"><span class="Identifier">AnotherObject</span></a> <span class="Other">=</span> <span class="Keyword">object</span>
+  <dt><pre><a href="#AnotherObject"><span class="Identifier">AnotherObject</span></a> <span class="Other">=</span> <span class="Keyword">object</span>
   <span class="Keyword">case</span> <span class="Identifier">x</span><span class="Operator">*</span><span class="Other">:</span> <span class="Identifier">bool</span>
   <span class="Keyword">of</span> <span class="Identifier">true</span><span class="Other">:</span>
     <span class="Identifier">y</span><span class="Operator">*</span><span class="Other">:</span> <span class="Keyword">proc</span> <span class="Other">(</span><span class="Identifier">x</span><span class="Other">:</span> <span class="Identifier">string</span><span class="Other">)</span>
@@ -402,7 +402,7 @@
   </dd>
 </div>
 <div id="B">
-  <dt><pre><a href="testproject.html#B"><span class="Identifier">B</span></a> {.<span class="Identifier">inject</span>.} <span class="Other">=</span> <span class="Keyword">enum</span>
+  <dt><pre><a href="#B"><span class="Identifier">B</span></a> {.<span class="Identifier">inject</span>.} <span class="Other">=</span> <span class="Keyword">enum</span>
   <span class="Identifier">bB</span></pre></dt>
   <dd>
     
@@ -411,7 +411,7 @@
   </dd>
 </div>
 <div id="Foo">
-  <dt><pre><a href="testproject.html#Foo"><span class="Identifier">Foo</span></a> <span class="Other">=</span> <span class="Keyword">enum</span>
+  <dt><pre><a href="#Foo"><span class="Identifier">Foo</span></a> <span class="Other">=</span> <span class="Keyword">enum</span>
   <span class="Identifier">enumValueA2</span></pre></dt>
   <dd>
     
@@ -420,7 +420,7 @@
   </dd>
 </div>
 <div id="FooBuzz">
-  <dt><pre><a href="testproject.html#FooBuzz"><span class="Identifier">FooBuzz</span></a> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">deprecated</span><span class="Other">:</span> <span class="StringLit">&quot;FooBuzz msg&quot;</span></span>.} <span class="Other">=</span> <span class="Identifier">int</span></pre></dt>
+  <dt><pre><a href="#FooBuzz"><span class="Identifier">FooBuzz</span></a> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">deprecated</span><span class="Other">:</span> <span class="StringLit">&quot;FooBuzz msg&quot;</span></span>.} <span class="Other">=</span> <span class="Identifier">int</span></pre></dt>
   <dd>
     <div class="deprecation-message">
   <b>Deprecated:</b> FooBuzz msg
@@ -431,7 +431,7 @@
   </dd>
 </div>
 <div id="MyObject">
-  <dt><pre><a href="testproject.html#MyObject"><span class="Identifier">MyObject</span></a> <span class="Other">=</span> <span class="Keyword">object</span>
+  <dt><pre><a href="#MyObject"><span class="Identifier">MyObject</span></a> <span class="Other">=</span> <span class="Keyword">object</span>
   <span class="Identifier">someString</span><span class="Operator">*</span><span class="Other">:</span> <span class="Identifier">string</span>        <span class="Comment">## This is a string</span>
   <span class="Identifier">annotated</span><span class="Operator">*</span> {.<span class="Identifier">somePragma</span>.}<span class="Other">:</span> <span class="Identifier">string</span> <span class="Comment">## This is an annotated string</span></pre></dt>
   <dd>
@@ -441,7 +441,7 @@
   </dd>
 </div>
 <div id="Shapes">
-  <dt><pre><a href="testproject.html#Shapes"><span class="Identifier">Shapes</span></a> <span class="Other">=</span> <span class="Keyword">enum</span>
+  <dt><pre><a href="#Shapes"><span class="Identifier">Shapes</span></a> <span class="Other">=</span> <span class="Keyword">enum</span>
   <span class="Identifier">Circle</span><span class="Other">,</span>                   <span class="Comment">## A circle</span>
   <span class="Identifier">Triangle</span><span class="Other">,</span>                 <span class="Comment">## A three-sided shape</span>
   <span class="Identifier">Rectangle</span>                  <span class="Comment">## A four-sided shape</span></pre></dt>
@@ -452,7 +452,7 @@
   </dd>
 </div>
 <div id="T19396">
-  <dt><pre><a href="testproject.html#T19396"><span class="Identifier">T19396</span></a> <span class="Other">=</span> <span class="Keyword">object</span>
+  <dt><pre><a href="#T19396"><span class="Identifier">T19396</span></a> <span class="Other">=</span> <span class="Keyword">object</span>
   <span class="Identifier">a</span><span class="Operator">*</span><span class="Other">:</span> <span class="Identifier">int</span></pre></dt>
   <dd>
     
@@ -461,7 +461,7 @@
   </dd>
 </div>
 <div id="Xxx">
-  <dt><pre><a href="testproject.html#Xxx"><span class="Identifier">Xxx</span></a> <span class="Other">=</span> <span class="Keyword">object</span>
+  <dt><pre><a href="#Xxx"><span class="Identifier">Xxx</span></a> <span class="Other">=</span> <span class="Keyword">object</span>
   <span class="Identifier">field</span><span class="Operator">*</span><span class="Other">:</span> <span class="Identifier">int</span>
   <span class="Identifier">field3</span><span class="Operator">*</span><span class="Other">:</span> <span class="Identifier">int</span>               <span class="Comment">## Doc comment2</span></pre></dt>
   <dd>
@@ -477,7 +477,7 @@
   <h1><a class="toc-backref" href="#8">Vars</a></h1>
   <dl class="item">
     <div id="aVariable">
-  <dt><pre><a href="testproject.html#aVariable"><span class="Identifier">aVariable</span></a><span class="Other">:</span> <span class="Identifier">array</span><span class="Other">[</span><span class="DecNumber">1</span><span class="Other">,</span> <span class="Identifier">int</span><span class="Other">]</span></pre></dt>
+  <dt><pre><a href="#aVariable"><span class="Identifier">aVariable</span></a><span class="Other">:</span> <span class="Identifier">array</span><span class="Other">[</span><span class="DecNumber">1</span><span class="Other">,</span> <span class="Identifier">int</span><span class="Other">]</span></pre></dt>
   <dd>
     
     
@@ -485,7 +485,7 @@
   </dd>
 </div>
 <div id="someVariable">
-  <dt><pre><a href="testproject.html#someVariable"><span class="Identifier">someVariable</span></a><span class="Other">:</span> <span class="Identifier">bool</span></pre></dt>
+  <dt><pre><a href="#someVariable"><span class="Identifier">someVariable</span></a><span class="Other">:</span> <span class="Identifier">bool</span></pre></dt>
   <dd>
     
     This should be visible.
@@ -499,7 +499,7 @@
   <h1><a class="toc-backref" href="#10">Consts</a></h1>
   <dl class="item">
     <div id="C_A">
-  <dt><pre><a href="testproject.html#C_A"><span class="Identifier">C_A</span></a> <span class="Other">=</span> <span class="FloatNumber">0x7FF0000000000000'f64</span></pre></dt>
+  <dt><pre><a href="#C_A"><span class="Identifier">C_A</span></a> <span class="Other">=</span> <span class="FloatNumber">0x7FF0000000000000'f64</span></pre></dt>
   <dd>
     
     
@@ -507,7 +507,7 @@
   </dd>
 </div>
 <div id="C_B">
-  <dt><pre><a href="testproject.html#C_B"><span class="Identifier">C_B</span></a> <span class="Other">=</span> <span class="DecNumber">0o377'i8</span></pre></dt>
+  <dt><pre><a href="#C_B"><span class="Identifier">C_B</span></a> <span class="Other">=</span> <span class="DecNumber">0o377'i8</span></pre></dt>
   <dd>
     
     
@@ -515,7 +515,7 @@
   </dd>
 </div>
 <div id="C_C">
-  <dt><pre><a href="testproject.html#C_C"><span class="Identifier">C_C</span></a> <span class="Other">=</span> <span class="DecNumber">0o277'i8</span></pre></dt>
+  <dt><pre><a href="#C_C"><span class="Identifier">C_C</span></a> <span class="Other">=</span> <span class="DecNumber">0o277'i8</span></pre></dt>
   <dd>
     
     
@@ -523,7 +523,7 @@
   </dd>
 </div>
 <div id="C_D">
-  <dt><pre><a href="testproject.html#C_D"><span class="Identifier">C_D</span></a> <span class="Other">=</span> <span class="DecNumber">0o177777'i16</span></pre></dt>
+  <dt><pre><a href="#C_D"><span class="Identifier">C_D</span></a> <span class="Other">=</span> <span class="DecNumber">0o177777'i16</span></pre></dt>
   <dd>
     
     
@@ -611,7 +611,7 @@
 </div>
 <div id="bar-procs-all">
   <div id="bar">
-  <dt><pre><span class="Keyword">proc</span> <a href="#bar"><span class="Identifier">bar</span></a><span class="Other">(</span><span class="Identifier">f</span><span class="Other">:</span> <a href="testproject.html#FooBuzz"><span class="Identifier">FooBuzz</span></a><span class="Other">)</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
+  <dt><pre><span class="Keyword">proc</span> <a href="#bar"><span class="Identifier">bar</span></a><span class="Other">(</span><span class="Identifier">f</span><span class="Other">:</span> <a href="#FooBuzz"><span class="Identifier">FooBuzz</span></a><span class="Other">)</span> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
   <dd>
     
     
@@ -835,7 +835,7 @@ at indent 0
 </div>
 <div id="z1-procs-all">
   <div id="z1">
-  <dt><pre><span class="Keyword">proc</span> <a href="#z1"><span class="Identifier">z1</span></a><span class="Other">(</span><span class="Other">)</span><span class="Other">:</span> <a href="testproject.html#Foo"><span class="Identifier">Foo</span></a> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
+  <dt><pre><span class="Keyword">proc</span> <a href="#z1"><span class="Identifier">z1</span></a><span class="Other">(</span><span class="Other">)</span><span class="Other">:</span> <a href="#Foo"><span class="Identifier">Foo</span></a> {.<span><span class="Other pragmadots">...</span></span><span class="pragmawrap"><span class="Identifier">raises</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">tags</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span><span class="Other">,</span> <span class="Identifier">forbids</span><span class="Other">:</span> <span class="Other">[</span><span class="Other">]</span></span>.}</pre></dt>
   <dd>
     
     cz1

nimsuggest/nimsuggest.nim

@@ -1018,7 +1018,7 @@ proc outlineNode(graph: ModuleGraph, n: PNode, endInfo: TLineInfo, infoPairs: Su
   if n.kind == nkSym and n.sym.checkSymbol(n.info):
     graph.suggestResult(n.sym, n.sym.info, ideOutline, endInfo.line, endInfo.col)
     return true
-  elif n.kind == nkIdent:
+  elif n.kind in {nkIdent, nkAccQuoted}:
     let symData = findByTLineInfo(n.info, infoPairs)
     if symData != nil and symData.sym.checkSymbol(symData.info):
        let sym = symData.sym
@@ -1028,7 +1028,7 @@ proc outlineNode(graph: ModuleGraph, n: PNode, endInfo: TLineInfo, infoPairs: Su
 proc handleIdentOrSym(graph: ModuleGraph, n: PNode, endInfo: TLineInfo, infoPairs: SuggestFileSymbolDatabase): bool =
   result = false
   for child in n:
-    if child.kind in {nkIdent, nkSym}:
+    if child.kind in {nkIdent, nkAccQuoted, nkSym}:
       if graph.outlineNode(child, endInfo, infoPairs):
         return true
     elif child.kind == nkPostfix:

tests/align/talign.nim

@@ -168,4 +168,3 @@ for q in 0..100:
     new topArr[i]
     topArr[i].m.di.b = q
     doAssert(cast[uint](addr topArr[i].m.di) mod uint(alignof(DeepInner)) == 0)
-

tests/align/talign2.nim

@@ -0,0 +1,10 @@
+discard """
+  matrix: "--mm:refc -d:useGcAssert -d:useSysAssert; --mm:orc"
+"""
+
+block:
+  type U = object
+    d {.align: 16.}: int8
+  var e: seq[ref U]
+  for i in 0 ..< 10000: e.add(new U)
+  doAssert getTotalMem() <= 1052672 * 2

tests/arc/tcaseobj.nim

@@ -365,3 +365,28 @@ proc do2(x: int, e: ItemExt): seq[(string, ItemExt)] =
   do1(x).map(proc(v: (string, Item)): auto = (v[0], ItemExt(a: v[1], b: e.b)))
 
 doAssert $do2(0, ItemExt(a: Item(kind: 1, c: "second"), b: "third")) == """@[("zero", (a: (kind: 1, c: "first"), b: "third"))]"""
+
+block:
+  type RangeCrash = object
+    case x: range[0..7]
+    of 0..2:
+      a: string
+    else:
+      b: string
+
+  var rangeCrash = RangeCrash()
+  {.cast(uncheckedAssign).}:
+    rangeCrash.x = 5
+
+block:
+  type Discrim = distinct uint8
+  type DistinctCrash = object
+    case x: Discrim
+    of Discrim(0)..Discrim(2):
+      a: string
+    else:
+      b: string
+
+  var distinctCrash = DistinctCrash()
+  {.cast(uncheckedAssign).}:
+    distinctCrash.x = Discrim(5)

tests/arc/torcbench.nim

@@ -35,4 +35,5 @@ proc main() =
 
 main()
 GC_fullCollect()
-echo getOccupiedMem() < 10 * 1024 * 1024, " peak memory: ", getMaxMem() < 10 * 1024 * 1024
+when not defined(useMalloc):
+  echo getOccupiedMem() < 10 * 1024 * 1024, " peak memory: ", getMaxMem() < 10 * 1024 * 1024

tests/array/tarray.nim

@@ -605,3 +605,17 @@ block t18643:
   except IndexDefect:
     caught = true
   doAssert caught, "IndexDefect not caught!"
+
+
+# bug #25475
+block:
+  type N = object
+    b: seq[array[1'u, int]]
+  doAssert N(b: @[[0]]) == N(b: @[[0]])
+
+block:
+  var x: array[5..6, int] = [0, 1]
+  var y: array[1..2, int] = [0, 1]
+
+  doAssert x == y # compiles
+  doAssert @[x] == @[y]

tests/ccgbugs2/tcodegen.nim

@@ -56,3 +56,22 @@ proc main = # bug #24677
   for NDEBUG in 0..2:
     doAssert NDEBUG == NDEBUG
 main()
+
+block: # importc type inheritance
+  type
+    A {.inheritable, pure, bycopy, importc: "int".} = object
+    B {.importc: "int", bycopy.} = object of A
+
+  {.emit: """
+  int foo(int a) {
+    return 123;
+  }
+  """.}
+
+  proc foo(a: A): B {.importc, nodecl.}
+
+  var a: A
+  var b = foo(a)
+  doAssert(cast[cint](b) == 123)
+  var c = foo(b)
+  doAssert(cast[cint](c) == 123)

tests/codegen/titaniummangle_nim.nim

@@ -1,35 +1,7 @@
 discard """
   targets: "c"
   matrix: "--debugger:native --mangle:nim"
-  ccodecheck: "'testFunc__titaniummangle95nim_u1316'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u156'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u1305'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u241'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u1357'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u292'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u38'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u175'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u1302'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u1305'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u535'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u1294'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u336'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u425'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u308'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u129'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u320'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u223'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u545'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u543'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u895'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u1104'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u1155'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u636'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u705'"
-  ccodecheck: "'testFunc__titaniummangle95nim_u800'"
-  ccodecheck: "'new__titaniummangle95nim_u1320'"
-  ccodecheck: "'xxx__titaniummangle95nim_u1391'"
-  ccodecheck: "'xxx__titaniummangle95nim_u1394'"
+  ccodecheck: "'testFunc__titaniummangle95nim_u'"
 """
 
 #When debugging this notice that if one check fails, it can be due to any of the above.
@@ -48,7 +20,7 @@ type
 
   Container[T] = object
     data: T
-      
+
   Container2[T, T2] = object
     data: T
     data2: T2
@@ -57,7 +29,7 @@ type
 
   Coo = Foo
 
-  Doo = Boo | Foo 
+  Doo = Boo | Foo
 
   TestProc = proc(a:string): string
 
@@ -67,87 +39,87 @@ type EnumSample = enum
 type EnumAnotherSample = enum
   a, b, c
 
-proc testFunc(a: set[EnumSample]) = 
+proc testFunc(a: set[EnumSample]) =
   echo $a
 
-proc testFunc(a: typedesc) = 
+proc testFunc(a: typedesc) =
   echo $a
 
-proc testFunc(a: ptr Foo) = 
+proc testFunc(a: ptr Foo) =
   echo repr a
 
-proc testFunc(s: string, a: Coo) = 
+proc testFunc(s: string, a: Coo) =
   echo repr a
 
-proc testFunc(s: int, a: Comparable) = 
+proc testFunc(s: int, a: Comparable) =
   echo repr a
 
-proc testFunc(a: TestProc) = 
+proc testFunc(a: TestProc) =
   let b = ""
   echo repr a("")
 
-proc testFunc(a: ref Foo) = 
+proc testFunc(a: ref Foo) =
   echo repr a
 
-proc testFunc(b: Boo) = 
+proc testFunc(b: Boo) =
   echo repr b
 
-proc testFunc(a: ptr UncheckedArray[int]) = 
+proc testFunc(a: ptr UncheckedArray[int]) =
   echo repr a
 
-proc testFunc(a: ptr int) = 
+proc testFunc(a: ptr int) =
   echo repr a
 
-proc testFunc(a: ptr ptr int) = 
+proc testFunc(a: ptr ptr int) =
   echo repr a
 
-proc testFunc(e: FooTuple, str: cstring) = 
+proc testFunc(e: FooTuple, str: cstring) =
   echo e
 
-proc testFunc(e: (float, float)) = 
+proc testFunc(e: (float, float)) =
   echo e
 
-proc testFunc(e: EnumSample) = 
+proc testFunc(e: EnumSample) =
   echo e
 
-proc testFunc(e: var int) = 
+proc testFunc(e: var int) =
   echo e
 
-proc testFunc(e: var Foo, a, b: int32, refFoo: ref Foo) = 
+proc testFunc(e: var Foo, a, b: int32, refFoo: ref Foo) =
   echo e
 
-proc testFunc(xs: Container[int]) = 
+proc testFunc(xs: Container[int]) =
   let a = 2
   echo xs
 
-proc testFunc(xs: Container2[int32, int32]) = 
+proc testFunc(xs: Container2[int32, int32]) =
   let a = 2
   echo xs
 
-proc testFunc(xs: Container[Container2[int32, int32]]) = 
+proc testFunc(xs: Container[Container2[int32, int32]]) =
   let a = 2
   echo xs
 
-proc testFunc(xs: seq[int]) = 
+proc testFunc(xs: seq[int]) =
   let a = 2
   echo xs
 
-proc testFunc(xs: openArray[string]) = 
+proc testFunc(xs: openArray[string]) =
   let a = 2
   echo xs
 
-proc testFunc(xs: array[2, int]) = 
+proc testFunc(xs: array[2, int]) =
   let a = 2
   echo xs
 
-proc testFunc(e: EnumAnotherSample) = 
+proc testFunc(e: EnumAnotherSample) =
   echo e
 
-proc testFunc(a, b: int) = 
+proc testFunc(a, b: int) =
   echo "hola"
   discard
 
-proc testFunc(a: int, xs: varargs[string]) = 
+proc testFunc(a: int, xs: varargs[string]) =
   let a = 10
   for x in xs:
     echo x
@@ -155,7 +127,7 @@ proc testFunc(a: int, xs: varargs[string]) =
 proc xxx(v: static int) =
   echo v
 
-proc testFunc() = 
+proc testFunc() =
   var a = 2
   var aPtr = a.addr
   var foo = Foo()

tests/destructor/tcustomseqs.nim

@@ -40,7 +40,7 @@ proc `=destroy`*[T](x: var myseq[T]) =
     x.len = 0
     x.cap = 0
 
-proc `=`*[T](a: var myseq[T]; b: myseq[T]) =
+proc `=copy`*[T](a: var myseq[T]; b: myseq[T]) =
   if a.data == b.data: return
   if a.data != nil:
     `=destroy`(a)
@@ -66,6 +66,11 @@ proc `=sink`*[T](a: var myseq[T]; b: myseq[T]) =
   a.cap = b.cap
   a.data = b.data
 
+proc `=wasMoved`*[T](a: var myseq[T]) =
+  a.data = nil
+  a.len = 0
+  a.cap = 0
+
 proc resize[T](s: var myseq[T]) =
   if s.cap == 0: s.cap = 8
   else: s.cap = (s.cap * 3) shr 1
@@ -118,7 +123,7 @@ template `[]=`*[T](x: myseq[T]; i: Natural; y: T) =
 proc createSeq*[T](elems: varargs[T]): myseq[T] =
   result.cap = elems.len
   result.len = elems.len
-  result.data = cast[type(result.data)](alloc(result.cap * sizeof(T)))
+  result.data = cast[type(result.data)](alloc0(result.cap * sizeof(T)))
   inc allocCount
   when supportsCopyMem(T):
     copyMem(result.data, addr(elems[0]), result.cap * sizeof(T))

tests/generics/tgenerics_issues.nim

@@ -902,3 +902,15 @@ block: # issue #25494
       a, b, c
 
   foo[MyEnum]()
+
+block: # issue #25005
+  type
+    RpcResponse[T] = ref object
+      result: T
+
+  func testit[T](p: var ref T) =
+    p = new(T)
+
+  var v: RpcResponse[string]
+  testit(v)
+

tests/generics/tpointerprocs.nim

@@ -3,7 +3,7 @@ cmd: "nim check $options --hints:off $file"
 action: "reject"
 nimout:'''
 tpointerprocs.nim(22, 11) Error: 'foo' doesn't have a concrete type, due to unspecified generic parameters.
-tpointerprocs.nim(34, 14) Error: type mismatch: got <int>
+tpointerprocs.nim(34, 14) Error: type mismatch: got <typedesc[int]>
 but expected one of:
 proc foo(x: int | float; y: int or string): float
   first type mismatch at position: 2 in generic parameters

tests/generics/tself_type.nim

@@ -0,0 +1,48 @@
+# issue 16754
+
+type
+  Opt[T] = object
+    when T is ref:
+      val: T
+      x: int
+    else:
+      val: T
+      x: string
+
+type
+  Foo = ref object
+    x: Opt[Foo]
+
+  Bar = object
+    x: ref Opt[Bar]
+
+var f = Foo()
+assert f.x.x is int
+var b = Bar()
+assert b.x.x is string
+
+type
+  BazG[T] = object
+    x: int
+
+  BazGRef[T] = ref object
+    x: T
+
+  Baz = object
+    x: Opt[BazG[Baz]]
+    y: Opt[BazGRef[Baz]]
+
+var z = Baz()
+assert z.x.x is string
+assert z.y.x is int
+
+import options
+
+type
+  Person = ref object
+    parent: Option[Person]
+
+proc newPerson(parent: Option[Person]): Person =
+  Person(parent: parent)
+
+var person = newPerson(none(Person))

tests/iter/tclosureiter_objupconv_methodawait.nim

@@ -0,0 +1,12 @@
+discard """
+  cmd: "nim c $file"
+"""
+
+import std/asyncdispatch
+
+type
+  A {.inheritable.} = ref object
+  B = ref object of A
+
+method a(x: A): Future[A] {.async, base.} =
+  B(await a(B()))

tests/iter/tyieldintry.nim

@@ -559,17 +559,21 @@ block: # void iterator
       discard
   var a = it
 
-block: # Locals present in only 1 state should be on the stack
+block:
+  # Locals present in only 1 state should be on the stack
   proc checkOnStack(a: pointer, shouldBeOnStack: bool) =
-    # Quick and dirty way to check if a points to stack
-    var dummy = 0
-    let dummyAddr = addr dummy
-    let distance = abs(cast[int](dummyAddr) - cast[int](a))
-    const requiredDistance = 300
-    if shouldBeOnStack:
-      doAssert(distance <= requiredDistance, "a is not on stack, but should")
-    else:
-      doAssert(distance > requiredDistance, "a is on stack, but should not")
+    # bug #25596: the very fact we take the address prevents the local
+    # from being on the stack
+    when false:
+      # Quick and dirty way to check if a points to stack
+      var dummy = 0
+      let dummyAddr = addr dummy
+      let distance = abs(cast[int](dummyAddr) - cast[int](a))
+      const requiredDistance = 300
+      if shouldBeOnStack:
+        doAssert(distance <= requiredDistance, "a is not on stack, but should")
+      else:
+        doAssert(distance > requiredDistance, "a is on stack, but should not")
 
   iterator it(): int {.closure.} =
     var a = 1

tests/macros/tgettypeimpl_defaults.nim

@@ -0,0 +1,39 @@
+discard """
+nimout: '''
+ObjectTy
+  Empty
+  Empty
+  RecList
+    IdentDefs
+      Sym "noDefault"
+      Sym "int"
+      Empty
+    IdentDefs
+      Sym "withDefault"
+      Sym "string"
+      StrLit "Hello World"
+ProcTy
+  FormalParams
+    Sym "bool"
+    IdentDefs
+      Sym "foo"
+      Sym "string"
+      StrLit "Proc default"
+  Empty
+'''
+"""
+
+import std/macros
+
+type
+  FooBar = object
+    noDefault: int
+    withDefault = "Hello World"
+
+  SomeProc = proc (foo = "Proc default"): bool
+
+macro dumpBodies() =
+  echo bindSym("FooBar").getTypeImpl().treeRepr
+  echo bindSym("SomeProc").getTypeImpl().treeRepr
+
+dumpBodies()

tests/misc/tparseoptmodes.nim

@@ -0,0 +1,508 @@
+discard """
+  action: run
+"""
+
+import parseopt
+from std/sequtils import toSeq
+
+type Opt = tuple[kind: CmdLineKind, key, val: string]
+proc `$`(opt: Opt): string = "(" & $opt[0] & ", \"" & opt[1] & "\", \"" & opt[2] & "\")"
+
+proc collect(args: seq[string] | string;
+              shortNoVal: set[char] = {};
+              longNoVal: seq[string] = @[]): seq[(CliMode, seq[Opt])] =
+  for mode in CliMode:
+    var p =  parseopt.initOptParser(args,
+      shortNoVal = shortNoVal, longNoVal = longNoVal, mode = mode)
+    let res = toSeq(parseopt.getopt(p))
+    result.add (mode, res)
+
+proc check(name: string;
+            results: openArray[(CliMode, seq[Opt])];
+            expected: proc(m: CliMode): seq[Opt]) =
+  for (mode, res) in results:
+    doAssert res == expected(mode), "[" & $mode & "]: " & name & ":\n" & $res
+
+block:
+  # pcShortValAllowNextArg: separate option-argument for mandatory opt-arg.
+  let res = collect(@["-c", "4"], shortNoVal = {'a', 'b'})
+  proc expected(m: CliMode): seq[Opt] =
+   case m
+   of LaxMode: @[(cmdShortOption, "c", "4")]
+   of NimMode: @[(cmdShortOption, "c", ""), (cmdArgument, "4", "")]
+   of GnuMode: @[(cmdShortOption, "c", "4")]
+  check("short whitespace value", res, expected)
+
+block:
+  # No opt-arg knowledge: whitespace does not bind to short option.
+  let res = collect(@["-c", "4"])
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdShortOption, "c", ""), (cmdArgument, "4", "")]
+  check("short no-val whitespace value", res, expected)
+
+block:
+  # pcShortBundle + pcShortValAllowNextArg: grouped shorts with one opt-arg.
+  let res = collect(@["-abc", "4"], shortNoVal = {'a', 'b'})
+  proc expected(m: CliMode): seq[Opt] =
+     case m
+     of LaxMode:    @[(cmdShortOption, "a", ""),
+                      (cmdShortOption, "b", ""),
+                      (cmdShortOption, "c", "4")]
+
+     of NimMode:    @[(cmdShortOption, "a", ""),
+                      (cmdShortOption, "b", ""),
+                      (cmdShortOption, "c", ""),
+                      (cmdArgument, "4", "")]
+
+     of GnuMode:    @[(cmdShortOption, "a", ""),
+                      (cmdShortOption, "b", ""),
+                      (cmdShortOption, "c", "4")]
+  check("short bundle with trailing value", res, expected)
+
+block:
+  # pcShortValAllowAdjacent: option+argument in same token (dash-led value).
+  let res = collect(@["-c-x"], shortNoVal = {'a', 'b'})
+  proc expected(m: CliMode): seq[Opt] =
+     @[(cmdShortOption, "c", "-x")]
+  check("short adjacent dash-led", res, expected)
+
+block:
+  # pcShortBundle + pcShortValAllowAdjacent (dash-led value).
+  let res = collect(@["-abc-10"], shortNoVal = {'a', 'b'})
+  proc expected(m: CliMode): seq[Opt] =
+     @[(cmdShortOption, "a", ""),
+       (cmdShortOption, "b", ""),
+       (cmdShortOption, "c", "-10")]
+  check("short bundle with adjacent negative", res, expected)
+
+block:
+  # pcShortValAllowNextArg: option and option-argument can be separate args.
+  let res = collect(@["-c", ":"], shortNoVal = {'a', 'b'})
+  proc expected(m: CliMode): seq[Opt] =
+     case m
+     of LaxMode: @[(cmdShortOption, "c", ":")]
+     of NimMode: @[(cmdShortOption, "c", ""), (cmdArgument, ":", "")]
+     of GnuMode: @[(cmdShortOption, "c", ":")]
+  check("short whitespace colon value", res, expected)
+
+block:
+  # pcShortValAllowAdjacent: combined option+argument without blanks.
+  let res = collect(@["-abc4"], shortNoVal = {'a', 'b'})
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdShortOption, "a", ""),
+      (cmdShortOption, "b", ""),
+      (cmdShortOption, "c", "4")]
+  check("short bundle adjacent value", res, expected)
+
+block:
+  # pcShortBundle: bundle of no-arg shorts should split into options.
+  let res = collect(@["-ab"], shortNoVal = {'a', 'b'})
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdShortOption, "a", ""), (cmdShortOption, "b", "")]
+  check("short bundle no-arg", res, expected)
+
+block:
+  # pcShortBundle + pcShortValAllowNextArg: a no-arg short followed by one with arg.
+  let res = collect(@["-ac", "4"], shortNoVal = {'a', 'b'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode   : @[(cmdShortOption, "a", ""),
+                       (cmdShortOption, "c", "4")]
+      of NimMode:    @[(cmdShortOption, "a", ""),
+                       (cmdShortOption, "c", ""),
+                       (cmdArgument, "4", "")]
+      of GnuMode:    @[(cmdShortOption, "a", ""),
+                       (cmdShortOption, "c", "4")]
+  check("short bundle trailing value", res, expected)
+
+block:
+  # pcShortValAllowNextArg + cmdline parsing: whitespace-separated opt-arg.
+  let res = collect("-c \"foo bar\"", shortNoVal = {'a', 'b'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode: @[(cmdShortOption, "c", "foo bar")]
+      of NimMode: @[(cmdShortOption, "c", ""), (cmdArgument, "foo bar", "")]
+      of GnuMode: @[(cmdShortOption, "c", "foo bar")]
+  check("short whitespace quoted value", res, expected)
+
+block:
+  # pcShortValAllowNextArg + pcShortValAllowDashLeading: negative numbers as opt-args.
+  let res = collect(@["-n", "-10"], shortNoVal = {'a', 'b', 'c'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:  @[(cmdShortOption, "n", "-10")]
+      of NimMode:  @[(cmdShortOption, "n", ""), (cmdShortOption, "1", "0")]
+      of GnuMode:  @[(cmdShortOption, "n", "-10")]
+  check("short negative value, shortNoVal used", res, expected)
+
+block:
+  # pcShortValAllowNextArg + pcShortValAllowDashLeading: negative numbers as opt-args.
+  let res = collect(@["-n", "-10"])
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:    @[(cmdShortOption, "n", ""),
+                       (cmdShortOption, "1", ""),
+                       (cmdShortOption, "0", "")]
+      of NimMode:    @[(cmdShortOption, "n", ""),
+                       (cmdShortOption, "1", ""),
+                       (cmdShortOption, "0", "")]
+      of GnuMode:    @[(cmdShortOption, "n", ""),
+                       (cmdShortOption, "1", ""),
+                       (cmdShortOption, "0", "")]
+  check("short negative value, shortNoVal empty", res, expected)
+
+block:
+  # pcShortValAllowNextArg: repeated option-argument pairs are interpreted in order.
+  let res = collect(@["-c", "1", "-c", "2"], shortNoVal = {'a', 'b'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:    @[(cmdShortOption, "c", "1"),
+                       (cmdShortOption, "c", "2")]
+      of NimMode:    @[(cmdShortOption, "c", ""),
+                       (cmdArgument, "1", ""),
+                       (cmdShortOption, "c", ""),
+                       (cmdArgument, "2", "")]
+      of GnuMode:    @[(cmdShortOption, "c", "1"),
+                       (cmdShortOption, "c", "2")]
+  check("short repeat whitespace values", res, expected)
+
+block:
+  # pcShortValAllowAdjacent: adjacent opt-args preserve order for repeats.
+  let res = collect(@["-c1", "-c2"], shortNoVal = {'a', 'b'})
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdShortOption, "c", "1"), (cmdShortOption, "c", "2")]
+  check("short repeat adjacent values", res, expected)
+
+block:
+  # pcShortValAllowDashLeading: value starting with '-' is consumed as opt-arg.
+  # Divergence from POSIX Guideline 14 when enabled.
+  let res = collect(@["-c", "-a"], shortNoVal = {'b'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode: @[(cmdShortOption, "c", "-a")]
+      of NimMode: @[(cmdShortOption, "c", ""), (cmdShortOption, "a", "")]
+      of GnuMode: @[(cmdShortOption, "c", "-a")]
+  check("short dash-led value", res, expected)
+
+block:
+  # Separator overrides shortNoVal
+  let res = collect(@["-a=foo"], shortNoVal = {'a'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode: @[(cmdShortOption, "a", "foo")]
+      of NimMode: @[(cmdShortOption, "a", "foo")]
+      of GnuMode: @[(cmdShortOption, "a", "=foo")]
+  check("separator suppresses shortNoVal", res, expected)
+
+block:
+  let res = collect(@["-a=foo"], shortNoVal = {'v'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode: @[(cmdShortOption, "a", "foo")]
+      of NimMode: @[(cmdShortOption, "a", "foo")]
+      of GnuMode: @[(cmdShortOption, "a", "=foo")]
+  check("adjacent value-taking vs chort option bundling 1", res, expected)
+
+block:
+  # pcLongAllowSep, mixed long/short parsing.
+  # Option-arguments may include ':'/'=' chars.
+  let args = @[
+    "foo bar",
+    "--path:/i like space/projects",
+    "--aa:bar=a",
+    "--a=c:d",
+    "--ab",
+    "-c",
+    "--a[baz]:doo"
+  ]
+  let res = collect(args, shortNoVal = {'c'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode: @[
+        (cmdArgument, "foo bar", ""),
+        (cmdLongOption, "path", "/i like space/projects"),
+        (cmdLongOption, "aa", "bar=a"),
+        (cmdLongOption, "a", "c:d"),
+        (cmdLongOption, "ab", ""),
+        (cmdShortOption, "c", ""),
+        (cmdLongOption, "a[baz]", "doo")]
+      of NimMode: @[
+        (cmdArgument, "foo bar", ""),
+        (cmdLongOption, "path", "/i like space/projects"),
+        (cmdLongOption, "aa", "bar=a"),
+        (cmdLongOption, "a", "c:d"),
+        (cmdLongOption, "ab", ""),
+        (cmdShortOption, "c", ""),
+        (cmdLongOption, "a[baz]", "doo")]
+      of GnuMode: @[
+        (cmdArgument, "foo bar", ""),
+        (cmdLongOption, "path:/i", ""), # longNoVal is empty so can't take arg here
+        (cmdArgument, "like space/projects", ""),
+        (cmdLongOption, "aa:bar", "a"),
+        (cmdLongOption, "a", "c:d"),
+        (cmdLongOption, "ab", ""),
+        (cmdShortOption, "c", ""),
+        (cmdLongOption, "a[baz]:doo", "")]
+  check("mixed long/short argv tokens", res, expected)
+
+
+block:
+  # pcLongAllowSep + separators: long option separator handling.
+  let res = collect(@["--foo:bar"])
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:      @[(cmdLongOption, "foo", "bar")]
+      of NimMode:      @[(cmdLongOption, "foo", "bar")]
+      of GnuMode:      @[(cmdLongOption, "foo:bar", "")]
+  check("long option colon separator", res, expected)
+
+block:
+  # pcLongAllowSep + separators: long option separator handling.
+  let res = collect(@["--foo= bar"])
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:      @[(cmdLongOption, "foo", "bar")]
+      of NimMode:      @[(cmdLongOption, "foo", "bar")]
+      of GnuMode:      @[(cmdLongOption, "foo", " bar")]
+  check("long option whitespace around separators", res, expected)
+
+block:
+  let res = collect(@["--foo =bar"])
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:      @[(cmdLongOption, "foo", "bar")]
+      of NimMode:      @[(cmdLongOption, "foo", "bar")]
+      of GnuMode:      @[(cmdLongOption, "foo", ""), (cmdArgument, "=bar", "")]
+  check("long option whitespace around separators", res, expected)
+
+block:
+  let res = collect("--foo =bar", longNoVal = @[""])
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdLongOption, "foo", "=bar")]
+  check("long option argument delimited with whitespace, val allowed", res, expected)
+
+block:
+  let res = collect("--foo =bar")
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdLongOption, "foo", ""), (cmdArgument, "=bar", "")]
+  check("long option argument delimited with whitespace, val not allowed", res, expected)
+
+block:
+  # pcLongAllowSep: '=' separator
+  let res = collect(@["--foo=bar"])
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdLongOption, "foo", "bar")]
+  check("long option equals separator", res, expected)
+
+block:
+  # pcLongValAllowNextArg: long option value can be next argument.
+  let res = collect(@["--foo", "bar"], longNoVal = @[""])
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdLongOption, "foo", "bar")]
+  check("long option next-arg value", res, expected)
+
+block:
+  # longNoVal disables next-arg value consumption.
+  let res = collect(@["--foo", "bar"], longNoVal = @["foo"])
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdLongOption, "foo", ""), (cmdArgument, "bar", "")]
+  check("long option longNoVal disables argument taking", res, expected)
+
+block:
+  # "--" is parsed as a long option with an empty key.
+  let res = collect(@["--", "rest"])
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdLongOption, "", ""), (cmdArgument, "rest", "")]
+  check("double-dash marker", res, expected)
+
+block:
+  # option values beginning with ':' - doubled up
+  let res = collect(@["--foo::"])
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode: @[(cmdLongOption, "foo", ":")]
+      of NimMode: @[(cmdLongOption, "foo", ":")]
+      of GnuMode: @[(cmdLongOption, "foo::", "")]
+  check("long option value starting with colon (doubled)", res, expected)
+
+block:
+  # option values beginning with '=' - doubled up
+  let res = collect(@["--foo=="])
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdLongOption, "foo", "=")]
+  check("long option value starting with equals (doubled)", res, expected)
+
+block:
+  # option values beginning with ':' - alternated with '='
+  let res = collect(@["--foo=:"])
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdLongOption, "foo", ":")]
+  check("long option value starting with colon (alternated)", res, expected)
+
+block:
+  # option values beginning with '=' - alternated with ':'
+  let res = collect(@["--foo:="])
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode: @[(cmdLongOption, "foo", "=")]
+      of NimMode: @[(cmdLongOption, "foo", "=")]
+      of GnuMode: @[(cmdLongOption, "foo:", "")]
+  check("long option value starting with equals (alternated)", res, expected)
+
+block issue9619:
+  let res = collect(@["--option=", "", "--anotherOption", "tree"])
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:    @[(cmdLongOption, "option", ""),
+                       (cmdLongOption, "anotherOption", ""),
+                       (cmdArgument, "tree", "")]
+      of NimMode:    @[(cmdLongOption, "option", ""),
+                       (cmdLongOption, "anotherOption", ""),
+                       (cmdArgument, "tree", "")]
+      of GnuMode:    @[(cmdLongOption, "option", ""),
+                       (cmdArgument, "", ""),
+                       (cmdLongOption, "anotherOption", ""),
+                       (cmdArgument, "tree", "")]
+  check("issue #9619, whitespace after separator", res, expected)
+
+
+block issue22736:
+  let res = collect(@["--long", "", "-h", "--long:", "-h", "--long=", "-h", "arg"])
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:    @[(cmdLongOption, "long", ""),
+                       (cmdArgument, "", ""),
+                       (cmdShortOption, "h", ""),
+                       (cmdLongOption, "long", "-h"),
+                       (cmdLongOption, "long", "-h"),
+                       (cmdArgument, "arg", "")]
+      of NimMode:    @[(cmdLongOption, "long", ""),
+                       (cmdArgument, "", ""),
+                       (cmdShortOption, "h", ""),
+                       (cmdLongOption, "long", "-h"),
+                       (cmdLongOption, "long", "-h"),
+                       (cmdArgument, "arg", "")]
+      of GnuMode:    @[(cmdLongOption, "long", ""),
+                       (cmdArgument, "", ""),
+                       (cmdShortOption, "h", ""),
+                       (cmdLongOption, "long:", ""),
+                       (cmdShortOption, "h", ""),
+                       (cmdLongOption, "long", ""),
+                       (cmdShortOption, "h", ""),
+                       (cmdArgument, "arg", "")]
+  check("issue #22736, whitespace after separator, colon separator", res, expected)
+
+# Numbers =====================================================================
+
+block:
+  # Positive integer adjacent to option
+  let res = collect("-n42", shortNoVal = {'v'})
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdShortOption, "n", "42")]
+  check("numerical option: positive integer adjacent", res, expected)
+
+block:
+  # Positive integer adjacent to  no-val option
+  let res = collect("-n42x", shortNoVal = {'n'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:  @[(cmdShortOption, "n", ""), (cmdShortOption, "4", "2x")]
+      of NimMode:  @[(cmdShortOption, "n", ""), (cmdShortOption, "4", "2x")]
+      of GnuMode:  @[(cmdShortOption, "n", ""), (cmdShortOption, "4", "2x")]
+  check("numerical no-val option: positive integer adjacent", res, expected)
+
+block:
+  # Negative integer adjacent to option
+  let res = collect("-n-42", shortNoVal = {'v'})
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdShortOption, "n", "-42")]
+  check("numerical option: negative integer adjacent", res, expected)
+
+block:
+  # Floating point number as value
+  let res = collect(@["-n", "3.14"], shortNoVal = {'v'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:      @[(cmdShortOption, "n", "3.14")]
+      of NimMode:      @[(cmdShortOption, "n", ""), (cmdArgument, "3.14", "")]
+      of GnuMode:      @[(cmdShortOption, "n", "3.14")]
+  check("numerical option: floating point whitespace", res, expected)
+
+block:
+  # Floating point adjacent to option
+  let res = collect(@["-n3.14"], shortNoVal = {'v'})
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdShortOption, "n", "3.14")]
+  check("numerical option: floating point adjacent", res, expected)
+
+block:
+  # Negative floating point
+  let res = collect(@["-n", "-3.14"], shortNoVal = {'v'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:      @[(cmdShortOption, "n", "-3.14")]
+      of NimMode:      @[(cmdShortOption, "n", ""), (cmdShortOption, "3", ".14")]
+      of GnuMode:      @[(cmdShortOption, "n", "-3.14")]
+  check("numerical option: negative floating point whitespace", res, expected)
+
+block:
+  # Negative floating point adjacent
+  let res = collect("-n-3.14", shortNoVal = {'v'})
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdShortOption, "n", "-3.14")]
+  check("numerical option: negative floating point adjacent", res, expected)
+
+block:
+  # Large number
+  let res = collect(@["-n", "414"], shortNoVal = {'v'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:      @[(cmdShortOption, "n", "414")]
+      of NimMode:      @[(cmdShortOption, "n", ""), (cmdArgument, "414", "")]
+      of GnuMode:      @[(cmdShortOption, "n", "414")]
+  check("numerical option: large number", res, expected)
+
+
+block:
+  # Multiple numerical options
+  let res = collect("-n 10 -m20 -k= 30 -40", shortNoVal = {'v'})
+  proc expected(m: CliMode): seq[Opt] =
+    case m
+      of LaxMode:    @[(cmdShortOption, "n", "10"),
+                       (cmdShortOption, "m", "20"),
+                       (cmdShortOption, "k", ""),    # buggy but preserved
+                       (cmdArgument, "30", ""),
+                       (cmdShortOption, "4", "0")]
+      of NimMode:    @[(cmdShortOption, "n", ""),
+                       (cmdArgument, "10", ""),
+                       (cmdShortOption, "m", "20"),
+                       (cmdShortOption, "k", ""),   # buggy but preserved
+                       (cmdArgument, "30", ""),
+                       (cmdShortOption, "4", "0")]
+      of GnuMode:    @[(cmdShortOption, "n", "10"),
+                       (cmdShortOption, "m", "20"),
+                       (cmdShortOption, "k", "="),
+                       (cmdArgument, "30", ""),
+                       (cmdShortOption, "4", "0")]
+  check("numerical option: multiple options", res, expected)
+
+block:
+  # Long option with numerical value
+  let res = collect(@["--count=42"], longNoVal = @[])
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdLongOption, "count", "42")]
+  check("numerical option: long option with equals", res, expected)
+
+block:
+  # Long option with numerical value (whitespace)
+  let res = collect(@["--count", "42"], longNoVal = @[""])
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdLongOption, "count", "42")]
+  check("numerical option: long option with whitespace", res, expected)
+
+block:
+  # Long option with negative numerical value
+  let res = collect(@["--offset=-10"], longNoVal = @[])
+  proc expected(m: CliMode): seq[Opt] =
+    @[(cmdLongOption, "offset", "-10")]
+  check("numerical option: long option negative", res, expected)

tests/range/timplicitrangedownsizing.nim

@@ -70,4 +70,9 @@ var smallFloatRange: SmallFloat = SmallFloat(5.0)
 acceptWideFloat(smallFloatRange)  # OK - SmallFloat (0.0..10.0) fits in WideFloatRange (0.0..100.0)
 
 var wf: WideFloatRange
-wf = smallFloatRange  # OK - SmallFloat range fits in WideFloatRange
+wf = smallFloatRange  # OK - SmallFloat range fits in WideFloatRange
+
+proc foo(x: Natural) =
+  discard
+
+foo(12)

tests/range/timplicitrangedownsizing3.nim

@@ -0,0 +1,14 @@
+discard """
+  matrix: "--warning:systemRangeConversion --warningaserror:systemRangeConversion"
+"""
+
+proc foo(x: range[0..100]) = discard
+
+foo(12)
+
+type
+  Float = range[0.0..100.0]
+
+proc bar(x: Float) = discard
+
+bar(12.0)