fixes #20645 (#20646)

* fixes #20645

* better bugfix

compiler/semdata.nim

@@ -69,7 +69,7 @@ type
     efWantStmt, efAllowStmt, efDetermineType, efExplain,
     efWantValue, efOperand, efNoSemCheck,
     efNoEvaluateGeneric, efInCall, efFromHlo, efNoSem2Check,
-    efNoUndeclared, efIsDotCall
+    efNoUndeclared, efIsDotCall, efCannotBeDotCall
       # Use this if undeclared identifiers should not raise an error during
       # overload resolution.
 

compiler/semexprs.nim

@@ -1363,7 +1363,7 @@ proc tryReadingTypeField(c: PContext, n: PNode, i: PIdent, ty: PType): PNode =
   else:
     result = tryReadingGenericParam(c, n, i, ty)
 
-proc builtinFieldAccess(c: PContext, n: PNode, flags: TExprFlags): PNode =
+proc builtinFieldAccess(c: PContext; n: PNode; flags: var TExprFlags): PNode =
   ## returns nil if it's not a built-in field access
   checkSonsLen(n, 2, c.config)
   # tests/bind/tbindoverload.nim wants an early exit here, but seems to
@@ -1401,12 +1401,15 @@ proc builtinFieldAccess(c: PContext, n: PNode, flags: TExprFlags): PNode =
       # field access and we leave the compiler to compile a normal call:
       if getCurrOwner(c).kind != skMacro:
         n.typ = makeTypeFromExpr(c, n.copyTree)
+        flags.incl efCannotBeDotCall
         return n
       else:
         return nil
     else:
+      flags.incl efCannotBeDotCall
       return tryReadingTypeField(c, n, i, ty.base)
   elif isTypeExpr(n.sons[0]):
+    flags.incl efCannotBeDotCall
     return tryReadingTypeField(c, n, i, ty)
   elif ty.kind == tyError:
     # a type error doesn't have any builtin fields
@@ -1458,6 +1461,7 @@ proc builtinFieldAccess(c: PContext, n: PNode, flags: TExprFlags): PNode =
   if result == nil:
     let t = n[0].typ.skipTypes(tyDotOpTransparent)
     result = tryReadingGenericParam(c, n, i, t)
+    flags.incl efCannotBeDotCall
 
 proc dotTransformation(c: PContext, n: PNode): PNode =
   if isSymChoice(n[1]):
@@ -1474,9 +1478,11 @@ proc dotTransformation(c: PContext, n: PNode): PNode =
 proc semFieldAccess(c: PContext, n: PNode, flags: TExprFlags): PNode =
   # this is difficult, because the '.' is used in many different contexts
   # in Nim. We first allow types in the semantic checking.
-  result = builtinFieldAccess(c, n, flags - {efIsDotCall})
-  if result == nil or ((result.typ == nil or result.typ.skipTypes(abstractInst).kind != tyProc) and 
-      efIsDotCall in flags and callOperator notin c.features):
+  var f = flags - {efIsDotCall}
+  result = builtinFieldAccess(c, n, f)
+  if result == nil or ((result.typ == nil or result.typ.skipTypes(abstractInst).kind != tyProc) and
+      efIsDotCall in flags and callOperator notin c.features and
+      efCannotBeDotCall notin f):
     result = dotTransformation(c, n)
 
 proc buildOverloadedSubscripts(n: PNode, ident: PIdent): PNode =
@@ -1744,7 +1750,8 @@ proc semAsgn(c: PContext, n: PNode; mode=asgnNormal): PNode =
     # r.f = x
     # --> `f=` (r, x)
     let nOrig = n.copyTree
-    a = builtinFieldAccess(c, a, {efLValue})
+    var flags = {efLValue}
+    a = builtinFieldAccess(c, a, flags)
     if a == nil:
       a = propertyWriteAccess(c, n, nOrig, n[0])
       if a != nil: return a

tests/overload/toverl4.nim

@@ -1,5 +1,6 @@
 discard """
-  output: '''true'''
+  output: '''true
+5.0'''
 """
 
 #bug #592
@@ -89,3 +90,12 @@ proc does_fail(): Foo =
   result.bar(5, a)
 
 doAssert does_fail().bar == 0
+
+# bug #20645
+
+type Zzz[Gen] = object
+
+proc testZ(z: Zzz) =
+  echo z.Gen(5)
+
+testZ(Zzz[float]())