introduce a pre-processing pass for the concept bodies

fixes #4982
fixes #3805

close #3414

compiler/sem.nim

@@ -442,6 +442,7 @@ proc semConstBoolExpr(c: PContext, n: PNode): PNode =
     result = nn
 
 proc semGenericStmt(c: PContext, n: PNode): PNode
+proc semConceptBody(c: PContext, n: PNode): PNode
 
 include semtypes, semtempl, semgnrc, semstmts, semexprs
 

compiler/semdata.nim

@@ -40,6 +40,11 @@ type
     bracketExpr*: PNode       # current bracket expression (for ^ support)
     mapping*: TIdTable
 
+  TMatchedConcept* = object
+    candidateType*: PType
+    prev*: ptr TMatchedConcept
+    depth*: int
+
   TInstantiationPair* = object
     genericSym*: PSym
     inst*: PInstantiation
@@ -75,6 +80,7 @@ type
     importTable*: PScope       # scope for all imported symbols
     topLevelScope*: PScope     # scope for all top-level symbols
     p*: PProcCon               # procedure context
+    matchedConcept*: ptr TMatchedConcept # the current concept being matched
     friendModules*: seq[PSym]  # friend modules; may access private data;
                                # this is used so that generic instantiations
                                # can access private object fields
@@ -82,7 +88,6 @@ type
 
     ambiguousSymbols*: IntSet  # ids of all ambiguous symbols (cannot
                                # store this info in the syms themselves!)
-    inTypeClass*: int          # > 0 if we are in a user-defined type class
     inGenericContext*: int     # > 0 if we are in a generic type
     inUnrolledContext*: int    # > 0 if we are unrolling a loop
     compilesContextId*: int    # > 0 if we are in a ``compiles`` magic
@@ -277,7 +282,7 @@ proc makeTypeFromExpr*(c: PContext, n: PNode): PType =
   assert n != nil
   result.n = n
 
-proc newTypeWithSons2*(kind: TTypeKind, owner: PSym, sons: seq[PType]): PType =
+proc newTypeWithSons*(owner: PSym, kind: TTypeKind, sons: seq[PType]): PType =
   result = newType(kind, owner)
   result.sons = sons
 

compiler/semexprs.nim

@@ -705,7 +705,7 @@ proc afterCallActions(c: PContext; n, orig: PNode, flags: TExprFlags): PNode =
     analyseIfAddressTakenInCall(c, result)
     if callee.magic != mNone:
       result = magicsAfterOverloadResolution(c, result, flags)
-  if c.inTypeClass == 0:
+  if c.matchedConcept == nil:
     result = evalAtCompileTime(c, result)
 
 proc semIndirectOp(c: PContext, n: PNode, flags: TExprFlags): PNode =
@@ -2147,7 +2147,7 @@ proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
     let checks = if efNoEvaluateGeneric in flags: {checkUndeclared}
                  else: {checkUndeclared, checkModule, checkAmbiguity}
     var s = qualifiedLookUp(c, n, checks)
-    if c.inTypeClass == 0: semCaptureSym(s, c.p.owner)
+    if c.matchedConcept == nil: semCaptureSym(s, c.p.owner)
     result = semSym(c, n, s, flags)
     if s.kind in {skProc, skMethod, skConverter, skIterator}:
       #performProcvarCheck(c, n, s)

compiler/semfold.nim

@@ -594,8 +594,11 @@ proc foldConStrStr(m: PSym, n: PNode): PNode =
 
 proc newSymNodeTypeDesc*(s: PSym; info: TLineInfo): PNode =
   result = newSymNode(s, info)
-  result.typ = newType(tyTypeDesc, s.owner)
-  result.typ.addSonSkipIntLit(s.typ)
+  if s.typ.kind != tyTypeDesc:
+    result.typ = newType(tyTypeDesc, s.owner)
+    result.typ.addSonSkipIntLit(s.typ)
+  else:
+    result.typ = s.typ
 
 proc getConstExpr(m: PSym, n: PNode): PNode =
   result = nil

compiler/semgnrc.nim

@@ -34,7 +34,7 @@ type
 
 type
   TSemGenericFlag = enum
-    withinBind, withinTypeDesc, withinMixin
+    withinBind, withinTypeDesc, withinMixin, withinConcept
   TSemGenericFlags = set[TSemGenericFlag]
 
 proc semGenericStmt(c: PContext, n: PNode,
@@ -200,12 +200,13 @@ proc semGenericStmt(c: PContext, n: PNode,
     checkMinSonsLen(n, 1)
     let fn = n.sons[0]
     var s = qualifiedLookUp(c, fn, {})
-    if s == nil and withinMixin notin flags and
+    if  s == nil and
+        {withinMixin, withinConcept}*flags == {} and
         fn.kind in {nkIdent, nkAccQuoted} and
         considerQuotedIdent(fn).id notin ctx.toMixin:
       errorUndeclaredIdentifier(c, n.info, fn.renderTree)
 
-    var first = 0
+    var first = ord(withinConcept in flags)
     var mixinContext = false
     if s != nil:
       incl(s.flags, sfUsed)
@@ -471,3 +472,9 @@ proc semGenericStmt(c: PContext, n: PNode): PNode =
   ctx.toMixin = initIntset()
   result = semGenericStmt(c, n, {}, ctx)
   semIdeForTemplateOrGeneric(c, result, ctx.cursorInBody)
+
+proc semConceptBody(c: PContext, n: PNode): PNode =
+  var ctx: GenericCtx
+  ctx.toMixin = initIntset()
+  result = semGenericStmt(c, n, {withinConcept}, ctx)
+  semIdeForTemplateOrGeneric(c, result, ctx.cursorInBody)

compiler/seminst.nim

@@ -257,8 +257,8 @@ proc generateInstance(c: PContext, fn: PSym, pt: TIdTable,
   # NOTE: for access of private fields within generics from a different module
   # we set the friend module:
   c.friendModules.add(getModule(fn))
-  let oldInTypeClass = c.inTypeClass
-  c.inTypeClass = 0
+  let oldMatchedConcept = c.matchedConcept
+  c.matchedConcept = nil
   let oldScope = c.currentScope
   while not isTopLevel(c): c.currentScope = c.currentScope.parent
   result = copySym(fn, false)
@@ -319,5 +319,5 @@ proc generateInstance(c: PContext, fn: PSym, pt: TIdTable,
   c.currentScope = oldScope
   discard c.friendModules.pop()
   dec(c.instCounter)
-  c.inTypeClass = oldInTypeClass
+  c.matchedConcept = oldMatchedConcept
   if result.kind == skMethod: finishMethod(c, result)

compiler/semmagic.nim

@@ -110,7 +110,7 @@ proc uninstantiate(t: PType): PType =
     else: t
 
 proc evalTypeTrait(traitCall: PNode, operand: PType, context: PSym): PNode =
-  const skippedTypes = {tyTypeDesc}
+  const skippedTypes = {tyTypeDesc, tyAlias}
   let trait = traitCall[0]
   internalAssert trait.kind == nkSym
   var operand = operand.skipTypes(skippedTypes)
@@ -119,7 +119,7 @@ proc evalTypeTrait(traitCall: PNode, operand: PType, context: PSym): PNode =
     traitCall.sons[2].typ.skipTypes({tyTypeDesc})
 
   template typeWithSonsResult(kind, sons): PNode =
-    newTypeWithSons2(kind, context, sons).toNode(traitCall.info)
+    newTypeWithSons(context, kind, sons).toNode(traitCall.info)
 
   case trait.sym.name.s
   of "or", "|":

compiler/semstmts.nim

@@ -144,7 +144,7 @@ proc fixNilType(n: PNode) =
   n.typ = nil
 
 proc discardCheck(c: PContext, result: PNode) =
-  if c.inTypeClass > 0: return
+  if c.matchedConcept != nil: return
   if result.typ != nil and result.typ.kind notin {tyStmt, tyVoid}:
     if result.kind == nkNilLit:
       result.typ = nil
@@ -1761,7 +1761,7 @@ proc semStmtList(c: PContext, n: PNode, flags: TExprFlags): PNode =
     else:
       var expr = semExpr(c, n.sons[i], flags)
       n.sons[i] = expr
-      if c.inTypeClass > 0 and expr.typ != nil:
+      if c.matchedConcept != nil and expr.typ != nil:
         case expr.typ.kind
         of tyBool:
           if expr.kind == nkInfix and
@@ -1800,7 +1800,7 @@ proc semStmtList(c: PContext, n: PNode, flags: TExprFlags): PNode =
 
   if result.len == 1 and
      # concept bodies should be preserved as a stmt list:
-     c.inTypeClass == 0 and
+     c.matchedConcept == nil and
      # also, don't make life complicated for macros.
      # they will always expect a proper stmtlist:
      nfBlockArg notin n.flags and

compiler/semtypes.nim

@@ -1202,17 +1202,51 @@ proc semTypeClass(c: PContext, n: PNode, prev: PType): PType =
   # if n.sonsLen == 0: return newConstraint(c, tyTypeClass)
   if nfBase2 in n.flags:
     message(n.info, warnDeprecated, "use 'concept' instead; 'generic'")
-  result = newOrPrevType(tyUserTypeClass, prev, c)
-  result.n = n
-
   let
     pragmas = n[1]
     inherited = n[2]
 
+  result = newOrPrevType(tyUserTypeClass, prev, c)
+  var owner = getCurrOwner(c)
+  var candidateTypeSlot = newTypeWithSons(owner, tyAlias, @[c.errorType])
+  result.sons = @[candidateTypeSlot]
+  result.n = n
+
   if inherited.kind != nkEmpty:
     for n in inherited.sons:
       let typ = semTypeNode(c, n, nil)
-      result.sons.safeAdd(typ)
+      result.sons.add(typ)
+
+  openScope(c)
+  for param in n[0]:
+    var
+      dummyName: PNode
+      dummyType: PType
+
+    let modifier = case param.kind
+      of nkVarTy: tyVar
+      of nkRefTy: tyRef
+      of nkPtrTy: tyPtr
+      of nkStaticTy: tyStatic
+      of nkTypeOfExpr: tyTypeDesc
+      else: tyNone
+
+    if modifier != tyNone:
+      dummyName = param[0]
+      dummyType = c.makeTypeWithModifier(modifier, candidateTypeSlot)
+      if modifier == tyTypeDesc: dummyType.flags.incl tfExplicit
+    else:
+      dummyName = param
+      dummyType = candidateTypeSlot
+
+    internalAssert dummyName.kind == nkIdent
+    var dummyParam = newSym(if modifier == tyTypeDesc: skType else: skVar,
+                            dummyName.ident, owner, owner.info)
+    dummyParam.typ = dummyType
+    addDecl(c, dummyParam)
+
+  result.n.sons[3] = semConceptBody(c, n[3])
+  closeScope(c)
 
 proc semProcTypeWithScope(c: PContext, n: PNode,
                         prev: PType, kind: TSymKind): PType =

compiler/sigmatch.nim

@@ -607,14 +607,24 @@ proc matchUserTypeClass*(c: PContext, m: var TCandidate,
   var
     typeClass = ff.skipTypes({tyUserTypeClassInst})
     body = typeClass.n[3]
-  if c.inTypeClass > 4:
-    localError(body.info, $body & " too nested for type matching")
-    return nil
+    matchedConceptContext: TMatchedConcept
+    prevMatchedConcept = c.matchedConcept
+    prevCandidateType = typeClass[0][0]
+
+  if prevMatchedConcept != nil:
+    matchedConceptContext.prev = prevMatchedConcept
+    matchedConceptContext.depth = prevMatchedConcept.depth + 1
+    if prevMatchedConcept.depth > 4:
+      localError(body.info, $body & " too nested for type matching")
+      return nil
 
   openScope(c)
-  inc c.inTypeClass
+  matchedConceptContext.candidateType = a
+  typeClass[0].sons[0] = a
+  c.matchedConcept = addr(matchedConceptContext)
   defer:
-    dec c.inTypeClass
+    c.matchedConcept = prevMatchedConcept
+    typeClass[0].sons[0] = prevCandidateType
     closeScope(c)
 
   var typeParams: seq[(PSym, PType)]
@@ -658,33 +668,6 @@ proc matchUserTypeClass*(c: PContext, m: var TCandidate,
 
       addDecl(c, param)
 
-  for param in typeClass.n[0]:
-    var
-      dummyName: PNode
-      dummyType: PType
-
-    let modifier = case param.kind
-      of nkVarTy: tyVar
-      of nkRefTy: tyRef
-      of nkPtrTy: tyPtr
-      of nkStaticTy: tyStatic
-      of nkTypeOfExpr: tyTypeDesc
-      else: tyNone
-
-    if modifier != tyNone:
-      dummyName = param[0]
-      dummyType = c.makeTypeWithModifier(modifier, a)
-      if modifier == tyTypeDesc: dummyType.flags.incl tfExplicit
-    else:
-      dummyName = param
-      dummyType = a
-
-    internalAssert dummyName.kind == nkIdent
-    var dummyParam = newSym(if modifier == tyTypeDesc: skType else: skVar,
-                            dummyName.ident, typeClass.sym, typeClass.sym.info)
-    dummyParam.typ = dummyType
-    addDecl(c, dummyParam)
-
   var
     oldWriteHook: type(writelnHook)
     diagnostics: seq[string]
@@ -826,7 +809,7 @@ proc inferStaticParam*(c: var TCandidate, lhs: PNode, rhs: BiggestInt): bool =
     var inferred = newTypeWithSons(c.c, tyStatic, lhs.typ.sons)
     inferred.n = newIntNode(nkIntLit, rhs)
     put(c, lhs.typ, inferred)
-    if c.c.inTypeClass > 0:
+    if c.c.matchedConcept != nil:
       # inside concepts, binding is currently done with
       # direct mutation of the involved types:
       lhs.typ.n = inferred.n
@@ -916,7 +899,7 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
   assert(aOrig != nil)
 
   var
-    useTypeLoweringRuleInTypeClass = c.c.inTypeClass > 0 and
+    useTypeLoweringRuleInTypeClass = c.c.matchedConcept != nil and
                                      not c.isNoCall and
                                      f.kind != tyTypeDesc and
                                      tfExplicit notin aOrig.flags
@@ -965,7 +948,10 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
   # for example, but unfortunately `prepareOperand` is not called in certain
   # situation when nkDotExpr are rotated to nkDotCalls
 
-  if a.kind in {tyGenericInst, tyAlias} and
+  if aOrig.kind == tyAlias:
+    return typeRel(c, f, lastSon(aOrig))
+
+  if a.kind == tyGenericInst and
       skipTypes(f, {tyVar}).kind notin {
         tyGenericBody, tyGenericInvocation,
         tyGenericInst, tyGenericParam} + tyTypeClasses:
@@ -1106,7 +1092,7 @@ proc typeRel(c: var TCandidate, f, aOrig: PType,
 
       if fRange.rangeHasUnresolvedStatic:
         return inferStaticsInRange(c, fRange, a)
-      elif c.c.inTypeClass > 0 and aRange.rangeHasUnresolvedStatic:
+      elif c.c.matchedConcept != nil and aRange.rangeHasUnresolvedStatic:
         return inferStaticsInRange(c, aRange, f)
       else:
         if lengthOrd(fRange) != lengthOrd(aRange):

compiler/trees.nim

@@ -110,9 +110,11 @@ proc isDeepConstExpr*(n: PNode): bool =
 
 proc isRange*(n: PNode): bool {.inline.} =
   if n.kind in nkCallKinds:
-    if n[0].kind == nkIdent and n[0].ident.id == ord(wDotDot) or
-        n[0].kind in {nkClosedSymChoice, nkOpenSymChoice} and
-        n[0][1].sym.name.id == ord(wDotDot):
+    let callee = n[0]
+    if (callee.kind == nkIdent and callee.ident.id == ord(wDotDot)) or
+       (callee.kind == nkSym and callee.sym.name.id == ord(wDotDot)) or
+       (callee.kind in {nkClosedSymChoice, nkOpenSymChoice} and
+        callee[1].sym.name.id == ord(wDotDot)):
       result = true
 
 proc whichPragma*(n: PNode): TSpecialWord =

tests/concepts/t3414.nim

@@ -0,0 +1,22 @@
+type
+  View[T] = concept v
+    v.empty is bool
+    v.front is T
+    popFront v
+
+proc find(view: View; target: View.T): View =
+  result = view
+
+  while not result.empty:
+    if view.front == target:
+      return
+
+    mixin popFront
+    popFront result
+
+proc popFront[T](s: var seq[T]) = discard
+proc empty[T](s: seq[T]): bool = false
+
+var s1 = @[1, 2, 3]
+let s2 = s1.find(10)
+

tests/concepts/t4982.nim

@@ -0,0 +1,18 @@
+discard """
+errormsg: "undeclared identifier: 'x'"
+line: 10
+"""
+
+import typetraits # without this import the program compiles (and echos false)
+
+type
+  SomeTestConcept = concept t
+    x.name is string # typo: t.name was intended (which would result in echo true)
+
+type
+  TestClass = ref object of RootObj
+    name: string
+
+var test = TestClass(name: "mytest")
+echo $(test is SomeTestConcept)
+