Nil type check implementation (#15287)

* Nil checking
* Enable current older not nil checking again, run new checking only under flag, skip our test
* Enable tests, work on try/except and bugs, fix notnil tests

* Enable strictNotNil tests (currently with lowercase category) and add some expected output
* Work on try/except/finally: still some things unclear and a lot of code can raise out of try
* Fix the notnil build by going back to the old version of a test which I shouldn't have changed

* Fix test : use action compile
* Work on mutation and aliasing: not finished
* Render var parititions graph, try to understand it, fix a nilcheck if bug
* Rebase, progress on working with partitions
* Improve time logic
* Fix some bugs, use graph indices instead of symbol in nil map
* Fix bugs, test simpler ident aliasing for now, support two mutation levels
* Support ContentMutation and ReAssignment: for now just detect possible re assignment for var parameters of calls
* Enable several simple passing tests
* Cleanup a bit, fix condition/branch infix-related bug
* Remove some files, address some comments by Araq
* Use internalError and no quit for now
* Separate tests with expected warnings and with expected ok, fix a bug with if with a single branch related to copyMap
* Fix new data structures, bugs: make tests pass, disable some for now
* Work on fixing errors with non-sym nodes, aliasing: tests fail
* Work on alias support: simple set-based logic, todo more tests and ref sets?
* Use ref sets: TODO can we think of handle seq-s similar to varpartitions' Araq ones
* Handle defers in one place, stop raising in reverse to make an async test compile with strictNotNil, add a commented out test
* Dot expressions: call/reassignment. Other refactorings and distinct, SeqOfDistinct support. Checkout an older varpartitions
* Work on field tracking
* Backup : trying to fix bugs when running some stdlib stuff for running an async test
* Start a section about strict not nil checking in experimental manual
* Fix experimental strict not nil manual section and move it to another file based on Araq feedback
* Fix unstructured flow and double warning problems, fix manual, cleanup
* Fix if/elif/else : take in account structure according to Araq feedback
* Refactor a bit
* Work on bracket expr support, re-enable tests, clarify in manual/tests/implementation static index support for now
* Work on compiling stdlib and compiler with strictNotNil
* Small fixes to the manual for strictNotNil
* Fix idgen for strict check nil rebase
* Enable some simple tests, remove old stuff, comment out code/print
* Copy the original varpartitions source instead of my changes
* Remove some files

compiler/ast.nim

@@ -1004,7 +1004,7 @@ const
   ConstantDataTypes*: TTypeKinds = {tyArray, tySet,
                                     tyTuple, tySequence}
   NilableTypes*: TTypeKinds = {tyPointer, tyCString, tyRef, tyPtr,
-    tyProc, tyError}
+    tyProc, tyError} # TODO
   PtrLikeKinds*: TTypeKinds = {tyPointer, tyPtr} # for VM
   ExportableSymKinds* = {skVar, skConst, skProc, skFunc, skMethod, skType,
     skIterator,
@@ -1387,6 +1387,7 @@ proc newType*(kind: TTypeKind, id: ItemId; owner: PSym): PType =
       echo "KNID ", kind
       writeStackTrace()
 
+
 proc mergeLoc(a: var TLoc, b: TLoc) =
   if a.k == low(typeof(a.k)): a.k = b.k
   if a.storage == low(typeof(a.storage)): a.storage = b.storage
@@ -1952,9 +1953,13 @@ proc canRaise*(fn: PNode): bool =
   elif fn.kind == nkSym and fn.sym.magic == mEcho:
     result = true
   else:
-    result = fn.typ != nil and fn.typ.n != nil and ((fn.typ.n[0].len < effectListLen) or
-      (fn.typ.n[0][exceptionEffects] != nil and
-      fn.typ.n[0][exceptionEffects].safeLen > 0))
+    # TODO check for n having sons? or just return false for now if not
+    if fn.typ != nil and fn.typ.n != nil and fn.typ.n[0].kind == nkSym:
+      result = false
+    else:
+      result = fn.typ != nil and fn.typ.n != nil and ((fn.typ.n[0].len < effectListLen) or
+        (fn.typ.n[0][exceptionEffects] != nil and
+        fn.typ.n[0][exceptionEffects].safeLen > 0))
 
 proc toHumanStrImpl[T](kind: T, num: static int): string =
   result = $kind

compiler/lineinfos.nim

@@ -56,7 +56,7 @@ type
     warnLockLevel = "LockLevel", warnResultShadowed = "ResultShadowed",
     warnInconsistentSpacing = "Spacing",  warnCaseTransition = "CaseTransition",
     warnCycleCreated = "CycleCreated", warnObservableStores = "ObservableStores",
-    warnUser = "User",
+    warnUser = "User", warnStrictNotNil = "StrictNotNil",
 
     hintSuccess = "Success", hintSuccessX = "SuccessX", hintCC = "CC",
     hintLineTooLong = "LineTooLong", hintXDeclaredButNotUsed = "XDeclaredButNotUsed",
@@ -129,6 +129,7 @@ const
     warnCycleCreated: "$1",
     warnObservableStores: "observable stores to '$1'",
     warnUser: "$1",
+    warnStrictNotNil: "$1",
     hintSuccess: "operation successful: $#",
     # keep in sync with `testament.isSuccess`
     hintSuccessX: "${loc} lines; ${sec}s; $mem; $build build; proj: $project; out: $output",

compiler/options.nim

@@ -176,7 +176,8 @@ type
       ## Note: this feature can't be localized with {.push.}
     vmopsDanger,
     strictFuncs,
-    views
+    views,
+    strictNotNil
 
   LegacyFeature* = enum
     allowSemcheckedAstModification,

compiler/semobjconstr.nim

@@ -153,6 +153,7 @@ proc collectMissingFields(c: PContext, fieldsRecList: PNode,
       if assignment == nil:
         constrCtx.missingFields.add r.sym
 
+
 proc semConstructFields(c: PContext, n: PNode,
                         constrCtx: var ObjConstrContext,
                         flags: TExprFlags): InitStatus =

compiler/sempass2.nim

@@ -10,7 +10,7 @@
 import
   intsets, ast, astalgo, msgs, renderer, magicsys, types, idents, trees,
   wordrecg, strutils, options, guards, lineinfos, semfold, semdata,
-  modulegraphs, varpartitions, typeallowed
+  modulegraphs, varpartitions, typeallowed, nilcheck
 
 when defined(useDfa):
   import dfa
@@ -1344,7 +1344,10 @@ proc trackProc*(c: PContext; s: PSym, body: PNode) =
   when defined(useDfa):
     if s.name.s == "testp":
       dataflowAnalysis(s, body)
+                                                                                                                   
       when false: trackWrites(s, body)
+  if strictNotNil in c.features and s.kind == skProc:
+    checkNil(s, body, g.config, c.idgen)
 
 proc trackStmt*(c: PContext; module: PSym; n: PNode, isTopLevel: bool) =
   if n.kind in {nkPragma, nkMacroDef, nkTemplateDef, nkProcDef, nkFuncDef,

compiler/semtypes.nim

@@ -917,6 +917,7 @@ proc semAnyRef(c: PContext; n: PNode; kind: TTypeKind; prev: PType): PType =
     # check every except the last is an object:
     for i in isCall..<n.len-1:
       let ni = n[i]
+      # echo "semAnyRef ", "n: ", n, "i: ", i, "ni: ", ni
       if ni.kind == nkNilLit:
         isNilable = true
       else:
@@ -933,7 +934,7 @@ proc semAnyRef(c: PContext; n: PNode; kind: TTypeKind; prev: PType): PType =
     addSonSkipIntLit(result, t, c.idgen)
     if tfPartial in result.flags:
       if result.lastSon.kind == tyObject: incl(result.lastSon.flags, tfPartial)
-    #if not isNilable: result.flags.incl tfNotNil
+    # if not isNilable: result.flags.incl tfNotNil
     case wrapperKind
     of tyOwned:
       if optOwnedRefs in c.config.globalOptions:
@@ -1563,6 +1564,8 @@ proc semTypeClass(c: PContext, n: PNode, prev: PType): PType =
     if modifier != tyNone:
       dummyName = param[0]
       dummyType = c.makeTypeWithModifier(modifier, candidateTypeSlot)
+      # if modifier == tyRef:
+        # dummyType.flags.incl tfNotNil
       if modifier == tyTypeDesc:
         dummyType.flags.incl tfConceptMatchedTypeSym
         dummyType.flags.incl tfCheckedForDestructor
@@ -1747,9 +1750,11 @@ proc semTypeNode(c: PContext, n: PNode, prev: PType): PType =
           if n[2].kind != nkNilLit:
             localError(c.config, n.info,
               "Invalid syntax. When used with a type, 'not' can be followed only by 'nil'")
-          if notnil notin c.features:
+          if notnil notin c.features and strictNotNil notin c.features:
             localError(c.config, n.info,
-              "enable the 'not nil' annotation with {.experimental: \"notnil\".}")
+              "enable the 'not nil' annotation with {.experimental: \"notnil\".} or " &
+              "  the `strict not nil` annotation with {.experimental: \"strictNotNil\".} " &
+              "  the \"notnil\" one is going to be deprecated, so please use \"strictNotNil\"")
           let resolvedType = result.skipTypes({tyGenericInst, tyAlias, tySink, tyOwned})
           case resolvedType.kind
           of tyGenericParam, tyTypeDesc, tyFromExpr:

compiler/treetab.nim

@@ -12,8 +12,9 @@
 import
   hashes, ast, astalgo, types
 
-proc hashTree(n: PNode): Hash =
-  if n == nil: return
+proc hashTree*(n: PNode): Hash =
+  if n.isNil:
+    return
   result = ord(n.kind)
   case n.kind
   of nkEmpty, nkNilLit, nkType:
@@ -21,7 +22,7 @@ proc hashTree(n: PNode): Hash =
   of nkIdent:
     result = result !& n.ident.h
   of nkSym:
-    result = result !& n.sym.name.h
+    result = result !& n.sym.id
   of nkCharLit..nkUInt64Lit:
     if (n.intVal >= low(int)) and (n.intVal <= high(int)):
       result = result !& int(n.intVal)
@@ -33,6 +34,9 @@ proc hashTree(n: PNode): Hash =
   else:
     for i in 0..<n.len:
       result = result !& hashTree(n[i])
+  result = !$result
+  #echo "hashTree ", result
+  #echo n
 
 proc treesEquivalent(a, b: PNode): bool =
   if a == b:

compiler/varpartitions.nim

@@ -904,4 +904,4 @@ proc computeCursors*(s: PSym; n: PNode; config: ConfigRef) =
         discard "cannot cursor into a graph that is mutated"
       else:
         v.sym.flags.incl sfCursor
-        #echo "this is now a cursor ", v.sym, " ", par.s[rid].flags, " ", config $ v.sym.info
+        #echo "this is now a cursor ", v.sym, " ", par.s[rid].flags, " ", config $ v.sym.info