[clang] Don't emit uninstantiated templates with -fdump-record-layouts-complete

[daltenty]

Summary

A follow on to D104484, this blocks the emitting of some template cases
where we would hit an assert because though the type was complete,
the class template wasn't fully specialized and adds a test case for the
corresponding test case.

clang/lib/AST/Decl.cpp

 void RecordDecl::completeDefinition() {
   assert(!isCompleteDefinition() && "Cannot redefine record!");
   TagDecl::completeDefinition();
 
   ASTContext &Ctx = getASTContext();
 
   // Layouts are dumped when computed, so if we are dumping for all complete
   // types, we need to force usage to get types that wouldn't be used elsewhere.
-  if (Ctx.getLangOpts().DumpRecordLayoutsComplete)
+  if (Ctx.getLangOpts().DumpRecordLayoutsComplete &&
+      (!isa<CXXRecordDecl>(this) ||
+       !cast<CXXRecordDecl>(this)->getDescribedClassTemplate()))
     (void)Ctx.getASTRecordLayout(this);
 }
 
 /// isMsStruct - Get whether or not this record uses ms_struct layout.
 /// This which can be turned on with an attribute, pragma, or the
 /// -mms-bitfields command-line option.
 bool RecordDecl::isMsStruct(const ASTContext &C) const {
   return hasAttr<MSStructAttr>() || C.getLangOpts().MSBitfields == 1;

clang/test/Layout/dump-complete.cpp

 // RUN: %clang_cc1 -emit-llvm-only -fdump-record-layouts-complete %s | FileCheck %s
 
 struct a {
   int x;
 };
 
 struct b {
   char y;
 } foo;
 
 class c {};
 
 class d;
 
+template <class A>
+struct B : public A {};
+
+template <class C>
+struct D : public C {};
+
+template<> struct D<a>;
+
+template <class E>
+struct F : public E {};
+
+F<a> bar;
+
 // CHECK:          0 | struct a
 // CHECK:          0 | struct b
 // CHECK:          0 | class c
 // CHECK-NOT:      0 | class d
+// CHECK-NOT:      0 | struct B
+// CHECK-NOT:      0 | struct D
+// CHECK :         0 | struct F<struct a>