[ItaniumMangle] Mangle dependent __underlying_type correctly

We attempted to use the UnaryTransformType's UnderlyingType instead of
it's BaseType.  This is not correct for dependent UnaryTransformType
because the have no underlying type.

This fixes PR28045.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@272079 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 0 deletions

diff --git a/test/CodeGenCXX/mangle.cpp b/test/CodeGenCXX/mangle.cpp
index 5012c3b379..5d757102ed 100644
--- a/test/CodeGenCXX/mangle.cpp
+++ b/test/CodeGenCXX/mangle.cpp
@@ -1101,3 +1101,13 @@ struct c {
   // CHECK-LABEL: @_ZN6test541cC2EPNS0_Ut0_E
 };
 }
+
+namespace test55 {
+enum E { R };
+
+template <typename T>
+void fn(T, __underlying_type(T)) {}
+
+template void fn<E>(E, __underlying_type(E));
+// CHECK-LABEL: @_ZN6test552fnINS_1EEEEvT_U3eutS2_
+}