From 2a8e4dd977d514ac4e0ecc7e1318275b2d4c886b Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Wed, 25 Feb 2026 20:45:09 +0800
Subject: [PATCH] fixes #25407; SIGSEGV when compiling when with typedesc

---
 compiler/sem.nim | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/compiler/sem.nim b/compiler/sem.nim
index cdda93223a..9c1a541f28 100644
--- a/compiler/sem.nim
+++ b/compiler/sem.nim
@@ -491,7 +491,11 @@ proc semAfterMacroCall(c: PContext, call, macroResult: PNode,
                    renderTree(result, {renderNoComments}))
         result = newSymNode(errorSym(c, result))
       else:
-        result.typ = makeTypeDesc(c, typ)
+        # 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)
     else:
       if s.ast[genericParamsPos] != nil and retType.isMetaType: