couple cases of valid concept bindings (#24513)

see tests

---------

Co-authored-by: Andreas Rumpf <rumpf_a@web.de>

compiler/concepts.nim

@@ -89,29 +89,52 @@ proc existingBinding(m: MatchCon; key: PType): PType =
 
 proc conceptMatchNode(c: PContext; n: PNode; m: var MatchCon): bool
 
-proc matchType(c: PContext; f, a: PType; m: var MatchCon): bool
+proc matchType(c: PContext; f, ao: PType; m: var MatchCon): bool
+
+proc acceptsAllTypes(t: PType): bool=
+  result = false
+  if t.kind == tyAnything:
+    result = true
+  elif t.kind == tyGenericParam:
+    if tfImplicitTypeParam in t.flags:
+      result = true
+    if not t.hasElementType or t.elementType.kind == tyNone:
+      result = true
 
 proc matchKids(c: PContext; f, a: PType; m: var MatchCon, start=0): bool=
   result = true
   for i in start..<f.kidsLen - ord(f.kind == tyGenericInst):
     if not matchType(c, f[i], a[i], m): return false
 
-proc matchType(c: PContext; f, a: PType; m: var MatchCon): bool =
+proc matchType(c: PContext; f, ao: PType; m: var MatchCon): bool =
   ## The heart of the concept matching process. 'f' is the formal parameter of some
   ## routine inside the concept that we're looking for. 'a' is the formal parameter
   ## of a routine that might match.
   const
     ignorableForArgType = {tyVar, tySink, tyLent, tyOwned, tyGenericInst, tyAlias, tyInferred}
+  
+  var a = ao
+  
+  case a.kind
+  of tyGenericParam:
+    let binding = m.existingBinding(a)
+    if binding != nil:
+      a = binding
+  else:
+    discard
+  
   case f.kind
   of tyAlias:
     result = matchType(c, f.skipModifier, a, m)
   of tyTypeDesc:
     if isSelf(f):
-      #let oldLen = m.inferred.len
-      result = matchType(c, a, m.potentialImplementation, m)
-      #echo "self is? ", result, " ", a.kind, " ", a, " ", m.potentialImplementation, " ", m.potentialImplementation.kind
-      #m.inferred.setLen oldLen
-      #echo "A for ", result, " to ", typeToString(a), " to ", typeToString(m.potentialImplementation)
+      if m.magic in {mArrPut, mArrGet}:
+        result = false
+        if m.potentialImplementation.reduceToBase.kind in arrPutGetMagicApplies:
+          m.inferred.add((a, last m.potentialImplementation))
+          result = true
+      else:
+        result = matchType(c, a, m.potentialImplementation, m)
     else:
       if a.kind == tyTypeDesc and f.hasElementType == a.hasElementType:
         if f.hasElementType:
@@ -120,7 +143,6 @@ proc matchType(c: PContext; f, a: PType; m: var MatchCon): bool =
           result = true # both lack it
       else:
         result = false
-
   of tyGenericInvocation:
     result = false
     if a.kind == tyGenericInst and a.genericHead.kind == tyGenericBody:
@@ -142,7 +164,7 @@ proc matchType(c: PContext; f, a: PType; m: var MatchCon): bool =
             when logBindings: echo "A adding ", f, " ", ak
             m.inferred.add((f, ak))
         elif m.magic == mArrGet and ak.kind in {tyArray, tyOpenArray, tySequence, tyVarargs, tyCstring, tyString}:
-          when logBindings: echo "B adding ", f, " ", lastSon ak
+          when logBindings: echo "B adding ", f, " ", last ak
           m.inferred.add((f, last ak))
           result = true
         else:
@@ -355,6 +377,8 @@ proc conceptMatch*(c: PContext; concpt, arg: PType; bindings: var LayeredIdTable
   ## `C[S, T]` parent type that we look for. We need this because we need to store bindings
   ## for 'S' and 'T' inside 'bindings' on a successful match. It is very important that
   ## we do not add any bindings at all on an unsuccessful match!
+  if arg.containsUnresolvedType:
+    return false
   var m = MatchCon(inferred: @[], potentialImplementation: arg, concpt: concpt)
   result = conceptMatchNode(c, concpt.n.lastSon, m)
   if result:

compiler/sigmatch.nim

@@ -595,45 +595,6 @@ proc handleFloatRange(f, a: PType): TTypeRelation =
       else: result = isIntConv
     else: result = isNone
 
-proc reduceToBase(f: PType): PType =
-  #[
-    Returns the lowest order (most general) type that that is compatible with the input.
-    E.g.
-    A[T] = ptr object ... A -> ptr object
-    A[N: static[int]] = array[N, int] ... A -> array
-  ]#
-  case f.kind:
-  of tyGenericParam:
-    if f.len <= 0 or f.skipModifier == nil:
-      result = f
-    else:
-      result = reduceToBase(f.skipModifier)
-  of tyGenericInvocation:
-    result = reduceToBase(f.baseClass)
-  of tyCompositeTypeClass, tyAlias:
-    if not f.hasElementType or f.elementType == nil:
-      result = f
-    else:
-      result = reduceToBase(f.elementType)
-  of tyGenericInst:
-    result = reduceToBase(f.skipModifier)
-  of tyGenericBody:
-    result = reduceToBase(f.typeBodyImpl)
-  of tyUserTypeClass:
-    if f.isResolvedUserTypeClass:
-      result = f.base  # ?? idk if this is right
-    else:
-      result = f.skipModifier
-  of tyStatic, tyOwned, tyVar, tyLent, tySink:
-    result = reduceToBase(f.base)
-  of tyInferred:
-    # This is not true "After a candidate type is selected"
-    result = reduceToBase(f.base)
-  of tyRange:
-    result = f.elementType
-  else:
-    result = f
-
 proc genericParamPut(c: var TCandidate; last, fGenericOrigin: PType) =
   if fGenericOrigin != nil and last.kind == tyGenericInst and
      last.kidsLen-1 == fGenericOrigin.kidsLen:

compiler/types.nim

@@ -102,6 +102,9 @@ const
   # typedescX is used if we're sure tyTypeDesc should be included (or skipped)
   typedescPtrs* = abstractPtrs + {tyTypeDesc}
   typedescInst* = abstractInst + {tyTypeDesc, tyOwned, tyUserTypeClass}
+  
+  # incorrect definition of `[]` and `[]=` for these types in system.nim
+  arrPutGetMagicApplies* = {tyArray, tyOpenArray, tyString, tySequence, tyCstring, tyTuple}
 
 proc invalidGenericInst*(f: PType): bool =
   result = f.kind == tyGenericInst and skipModifier(f) == nil
@@ -2038,3 +2041,42 @@ proc genericRoot*(t: PType): PType =
       result = t.sym.typ
     else:
       result = nil
+
+proc reduceToBase*(f: PType): PType =
+  #[
+    Returns the lowest order (most general) type that that is compatible with the input.
+    E.g.
+    A[T] = ptr object ... A -> ptr object
+    A[N: static[int]] = array[N, int] ... A -> array
+  ]#
+  case f.kind:
+  of tyGenericParam:
+    if f.len <= 0 or f.skipModifier == nil:
+      result = f
+    else:
+      result = reduceToBase(f.skipModifier)
+  of tyGenericInvocation:
+    result = reduceToBase(f.baseClass)
+  of tyCompositeTypeClass, tyAlias:
+    if not f.hasElementType or f.elementType == nil:
+      result = f
+    else:
+      result = reduceToBase(f.elementType)
+  of tyGenericInst:
+    result = reduceToBase(f.skipModifier)
+  of tyGenericBody:
+    result = reduceToBase(f.typeBodyImpl)
+  of tyUserTypeClass:
+    if f.isResolvedUserTypeClass:
+      result = f.base  # ?? idk if this is right
+    else:
+      result = f.skipModifier
+  of tyStatic, tyOwned, tyVar, tyLent, tySink:
+    result = reduceToBase(f.base)
+  of tyInferred:
+    # This is not true "After a candidate type is selected"
+    result = reduceToBase(f.base)
+  of tyRange:
+    result = f.elementType
+  else:
+    result = f

tests/concepts/tconceptsv2.nim

@@ -5,6 +5,7 @@ B[system.int]
 A[system.string]
 A[array[0..0, int]]
 A[seq[int]]
+char
 '''
 """
 import conceptsv2_helper
@@ -128,3 +129,38 @@ block: # more complex recursion
 
   var a = BufferImpl[5]()
   launch(a, WritableImpl())
+
+block:  # capture p1[T]
+  type
+    A[T] = object
+    C = concept
+      proc p1(x: Self, i: int): float
+
+  proc p1[T](a: A[T], idx: int): T = default(T)
+  proc p(a: C): int = discard
+  proc p[T](a: T):int = assert false
+
+  discard p(A[float]())
+
+block:  # mArrGet binding
+  type
+    ArrayLike[T] = concept
+      proc len(x: Self): int
+      proc `[]`(b: Self, i: int): T
+
+  proc p[T](a: ArrayLike[T]): int= discard
+  discard p([1,2])
+
+block:
+  type
+    A[T] = object
+    ArrayLike[T] = concept
+      proc len(x: Self): int
+      proc `[]`(b: Self, i: int): T
+      proc tell(s: Self, x: A[int])
+  
+  proc tell(x: string, h: A[int])= discard
+
+  proc spring[T](w: ArrayLike[T])= echo T
+  
+  spring("hi")