add test for GH56652

Author: cor3ntin

clang/docs/ReleaseNotes.rst

@@ -379,7 +379,7 @@ Bug Fixes in This Version
 - Fixed an assertion when an improper use of the ``malloc`` attribute targeting
   a function without arguments caused us to try to access a non-existent argument.
   (#GH159080)
-- Fixed a failed assertion with empty filename arguments in ``__has_embed``. (#GH159898)
+- Fixed a failed assertion with empty filename arguments in ``__has_embed``. (#GH159898) (#GH56652)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

clang/test/CodeGenCXX/gh56652.cpp

@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -std=c++20 -triple x86_64-elf-gnu %s -emit-llvm -o - | FileCheck %s
+
+namespace GH56652{
+
+struct foo {};
+
+template <typename T> struct bar {
+    using type = T;
+
+    template <foo> inline static constexpr auto b = true;
+};
+
+template <typename T>
+concept C = requires(T a) { T::template b<foo{}>; };
+
+template <typename T> auto fn(T) {
+    if constexpr (!C<T>)
+        return foo{};
+    else
+        return T{};
+}
+
+auto a = decltype(fn(bar<int>{})){};
+
+}
+
+// CHECK: %"struct.GH56652::bar" = type { i8 }
+// CHECK: @_ZN7GH566521aE = global %"struct.GH56652::bar" undef