From 786720013595148a1e9a94fc718d8f8dc184f3ef Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Fri, 17 Apr 2026 19:09:38 +0800
Subject: [PATCH] normalizeTypedescMacroResult

---
 compiler/sem.nim | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/compiler/sem.nim b/compiler/sem.nim
index 9c1a541f28..553dc2454d 100644
--- a/compiler/sem.nim
+++ b/compiler/sem.nim
@@ -454,6 +454,25 @@ proc resetSemFlag(n: PNode) =
     for i in 0..<n.safeLen:
       resetSemFlag(n[i])
 
+proc normalizeTypedescMacroResult(c: PContext, n: PNode): PNode =
+  result = n
+  if result.kind == nkStmtList:
+    result.transitionSonsKind(nkStmtListType)
+
+  # Resolve surviving compile-time branches so later passes don't walk
+  # unevaluated type AST for a typedesc expression.
+  while true:
+    if result.kind == nkWhenStmt:
+      result = semWhen(c, result, false)
+      if result.kind == nkStmtList:
+        result.transitionSonsKind(nkStmtListType)
+    elif result.kind == nkStmtListType and result.len > 0 and result[^1].kind == nkWhenStmt:
+      result[^1] = semWhen(c, result[^1], false)
+      if result[^1].kind == nkStmtList:
+        result[^1].transitionSonsKind(nkStmtListType)
+    else:
+      break
+
 proc semAfterMacroCall(c: PContext, call, macroResult: PNode,
                        s: PSym, flags: TExprFlags; expectedType: PType = nil): PNode =
   ## Semantically check the output of a macro.
@@ -484,19 +503,14 @@ proc semAfterMacroCall(c: PContext, call, macroResult: PNode,
       # More restrictive version.
       result = semExprWithType(c, result, flags, expectedType)
     of tyTypeDesc:
-      if result.kind == nkStmtList: result.transitionSonsKind(nkStmtListType)
+      result = normalizeTypedescMacroResult(c, result)
       var typ = semTypeNode(c, result, nil)
       if typ == nil:
         localError(c.config, result.info, "expression has no type: " &
                    renderTree(result, {renderNoComments}))
         result = newSymNode(errorSym(c, result))
       else:
-        # Replace with a clean nkType node so that complex expressions
-        # (like `when` statements from template expansion) don't persist
-        # in the AST with potentially uninitialized children that would
-        # cause a SIGSEGV during the transform phase's constant folding.
-        result = newNodeIT(nkType, result.info, makeTypeDesc(c, typ))
-      #result = symNodeFromType(c, typ, n.info)
+        result.typ = makeTypeDesc(c, typ)
     else:
       if s.ast[genericParamsPos] != nil and retType.isMetaType:
         # The return type may depend on the Macro arguments