From 2fc23370ecae4cedd7b6038e839ed2cea47792ee Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Mon, 15 Sep 2025 21:03:22 +0800
Subject: [PATCH] fixes #24844; Invalid C codegen refc with generic types
 containing gc memory (#25160)

fixes #24844

it may not be used in other places except in `genTraverseProc`,
we have to generate a `typedesc` for this case, not a weak `typedec`

(cherry picked from commit a77d1cc6c1f69a8b50034bc8a8023e976263b2f4)
---
 compiler/ccgtypes.nim |  3 +++
 tests/refc/m24844.nim |  8 ++++++++
 tests/refc/t24844.nim | 11 +++++++++++
 3 files changed, 22 insertions(+)
 create mode 100644 tests/refc/m24844.nim
 create mode 100644 tests/refc/t24844.nim

diff --git a/compiler/ccgtypes.nim b/compiler/ccgtypes.nim
index eb1e46c460..989610d207 100644
--- a/compiler/ccgtypes.nim
+++ b/compiler/ccgtypes.nim
@@ -1886,6 +1886,9 @@ proc genTypeInfoV1(m: BModule; t: PType; info: TLineInfo): Rope =
   of tyRef:
     genTypeInfoAux(m, t, t, result, info)
     if m.config.selectedGC in {gcMarkAndSweep, gcRefc, gcGo}:
+      # it may not be used in other places except in `genTraverseProc`,
+      # we have to generate a typedesc for this case, not a weak one
+      discard getTypeDesc(m, origType.last)
       let markerProc = genTraverseProc(m, origType, sig)
       m.s[cfsTypeInit3].addf("$1.marker = $2;$n", [tiNameForHcr(m, result), markerProc])
   of tyPtr, tyRange, tyUncheckedArray: genTypeInfoAux(m, t, t, result, info)
diff --git a/tests/refc/m24844.nim b/tests/refc/m24844.nim
new file mode 100644
index 0000000000..59e709d24d
--- /dev/null
+++ b/tests/refc/m24844.nim
@@ -0,0 +1,8 @@
+type
+  S*[T] = ref object of RootObj
+    k: string
+  A*[T] = ref object of S[T]
+
+proc p*[T](): S[T] = S[T]()
+proc u*() = discard A[int]()
+discard A[int]()
\ No newline at end of file
diff --git a/tests/refc/t24844.nim b/tests/refc/t24844.nim
new file mode 100644
index 0000000000..1a60e94125
--- /dev/null
+++ b/tests/refc/t24844.nim
@@ -0,0 +1,11 @@
+discard """
+  matrix: "--mm:refc; --mm:arc"
+  joinable: false
+"""
+
+import m24844
+
+u()
+
+type E = distinct int
+discard p[E]()
\ No newline at end of file