[MS Demangler] Print template constructor args.

Previously if you had something like this:

template<typename T>
struct Foo {
  template<typename U>
  Foo(U);
};

Foo F(3.7);

this would mangle as ??$?0N@?$Foo@H@@QEAA@N@Z

and this would be demangled as:

undname:      __cdecl Foo<int>::Foo<int><double>(double)
llvm-undname: __cdecl Foo<int>::Foo<int>(double)

Note the lack of the constructor template parameter in our
demangling.

This patch makes it so we print the constructor argument list.

llvm-svn: 340356

llvm/lib/Demangle/MicrosoftDemangle.cpp

@@ -969,7 +969,20 @@ static void outputName(OutputStream &OS, const Name *TheName, const Type *Ty) {
     OS << "~";
     LLVM_FALLTHROUGH;
   case OperatorTy::Ctor:
+    // Output the class name with template arguments a second time.
     outputNameComponent(OS, *Previous);
+
+    // Structors don't have a name, so outputting the name here actually is a
+    // no-op.  But for template constructors, it needs to output the template
+    // argument list.  e.g.
+    //
+    // template<typename T>
+    // struct Foo {
+    //    template<typename U>
+    //    Foo(U);
+    // };
+    // should demangle as -- for example -- Foo<int><double>(double);
+    outputNameComponent(OS, *TheName);
     break;
   case OperatorTy::Conversion:
     OS << "operator";

llvm/test/Demangle/ms-templates.test

@@ -196,3 +196,6 @@
 
 ??$f@US@@$1?g@1@QEAAXXZ@@YAXXZ
 ; CHECK: void __cdecl f<struct S, &void __cdecl S::g(void)>(void)
+
+??$?0N@?$Foo@H@@QEAA@N@Z
+; CHECK: __cdecl Foo<int>::Foo<int><double>(double)