From 065f46afa81f8220697f30b0deeb5ea2beccf4be Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Wed, 6 May 2026 21:33:46 +0800
Subject: [PATCH] fixes #23765; Method calling proc with return value
 overlapping declared generic type generates invalid C

---
 compiler/seminst.nim        |  3 ++-
 compiler/semtypinst.nim     |  3 ++-
 tests/ccgbugs2/tcodegen.nim | 16 ++++++++++++++++
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/compiler/seminst.nim b/compiler/seminst.nim
index a34467636a..7d0585d444 100644
--- a/compiler/seminst.nim
+++ b/compiler/seminst.nim
@@ -81,7 +81,8 @@ proc sameInstantiation(a, b: TInstantiation): bool =
       if not compareTypes(a.concreteTypes[i], b.concreteTypes[i],
                           flags = {ExactTypeDescValues,
                                    ExactGcSafety,
-                                   PickyCAliases}): return
+                                   PickyCAliases,
+                                   PickyBackendAliases}): return
     result = true
   else:
     result = false
diff --git a/compiler/semtypinst.nim b/compiler/semtypinst.nim
index 5f846c80ac..326fbd63f7 100644
--- a/compiler/semtypinst.nim
+++ b/compiler/semtypinst.nim
@@ -52,7 +52,8 @@ proc searchInstTypes*(g: ModuleGraph; key: PType): PType =
       for j in FirstGenericParamAt..<key.kidsLen:
         # XXX sameType is not really correct for nested generics?
         if not compareTypes(inst[j], key[j],
-                            flags = {ExactGenericParams, PickyCAliases}):
+                            flags = {ExactGenericParams, PickyCAliases,
+                                     PickyBackendAliases}):
           break matchType
 
       return inst
diff --git a/tests/ccgbugs2/tcodegen.nim b/tests/ccgbugs2/tcodegen.nim
index bca361e813..70f8ba8d88 100644
--- a/tests/ccgbugs2/tcodegen.nim
+++ b/tests/ccgbugs2/tcodegen.nim
@@ -75,3 +75,19 @@ block: # importc type inheritance
   doAssert(cast[cint](b) == 123)
   var c = foo(b)
   doAssert(cast[cint](c) == 123)
+
+
+# bug #23765
+type
+  X11[T, E] = object
+    m: T
+  B = X11[culonglong, cstring]
+  S = ref object of RootObj
+
+proc j[T, E](m: X11[T, E]): T = discard
+proc n(T: typedesc[SomeUnsignedInt]): X11[T, cstring] = discard
+method call(client: S): uint64 {.base.} =
+  discard j(n(uint64))
+
+var s = S()
+discard s.call()
\ No newline at end of file