Better support for constructors with -cxx-abi microsoft, partly fixes PR12784

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176186 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/MicrosoftMangle.cpp b/lib/AST/MicrosoftMangle.cpp
index b0fc25c..8c31e57 100644
--- a/lib/AST/MicrosoftMangle.cpp
+++ b/lib/AST/MicrosoftMangle.cpp
@@ -503,6 +503,10 @@
       llvm_unreachable("Can't mangle Objective-C selector names here!");
       
     case DeclarationName::CXXConstructorName:
+      if (ND == Structor) {
+        assert(StructorType == Ctor_Complete &&
+               "Should never be asked to mangle a ctor other than complete");
+      }
       Out << "?0";
       break;