allow `untyped` arguments to fail to compile in overload mismatch error (#23984)

fixes #8697, fixes #9620, fixes #23265

When matching a `template` with an `untyped` argument fails because of a
mismatching typed argument, `presentFailedCandidates` tries to sem every
single argument to show their types, but trying to type the `untyped`
argument can fail if it's supposed to use an injected symbol, so we get
an unrelated error message like "undeclared identifier".

Instead we use `tryExpr` as the comment suggests, setting the type to
`untyped` if it fails to compile. We could also maybe check if an
`untyped` argument is expected in its place and not try to compile the
expression if it is but this would require a bit of reorganizing the
code here and IMO it's better to have the information of what type it
would be if it can be typed.

1 files changed, 17 insertions, 6 deletions

diff --git a/compiler/sigmatch.nim b/compiler/sigmatch.nim
index 744e0ff8b..a17869b87 100644
--- a/compiler/sigmatch.nim
+++ b/compiler/sigmatch.nim
@@ -338,16 +338,27 @@ template describeArgImpl(c: PContext, n: PNode, i: int, startIdx = 1; prefer = p
     result.add renderTree(n[i][0])
     result.add ": "
     if arg.typ.isNil and arg.kind notin {nkStmtList, nkDo}:
-      # XXX we really need to 'tryExpr' here!
-      arg = c.semOperand(c, n[i][1])
-      n[i].typ = arg.typ
-      n[i][1] = arg
+      arg = c.semTryExpr(c, n[i][1])
+      if arg == nil:
+        arg = n[i][1]
+        arg.typ = newTypeS(tyUntyped, c)
+      else:
+        if arg.typ == nil:
+          arg.typ = newTypeS(tyVoid, c)
+        n[i].typ = arg.typ
+        n[i][1] = arg
   else:
     if arg.typ.isNil and arg.kind notin {nkStmtList, nkDo, nkElse,
                                           nkOfBranch, nkElifBranch,
                                           nkExceptBranch}:
-      arg = c.semOperand(c, n[i])
-      n[i] = arg
+      arg = c.semTryExpr(c, n[i])
+      if arg == nil:
+        arg = n[i]
+        arg.typ = newTypeS(tyUntyped, c)
+      else:
+        if arg.typ == nil:
+          arg.typ = newTypeS(tyVoid, c)
+        n[i] = arg
   if arg.typ != nil and arg.typ.kind == tyError: return
   result.add argTypeToString(arg, prefer)