[lldb] Also set owning module for template specializations

[teemperor]

Summary

This was originally commented out as it broke the data-formatter-stl/libcxx/
tests. However this was fixed by commit ef423a3ba57045f80b0fcafce72121449a8b54d4
(Add Objective-C property accessors loaded from Clang module DWARF to lookup)
which sets the HasExternalVisibleStorage flag for the template specializations.

[teemperor]

• Updated module-ownership test

[aprantl]

Cool! After searching for a solution that long, it's really weird to learn that I accidentally fixed it by setting ExternalVisibleDecls.

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp

class_template_specialization_decl->setTagKind(
       static_cast<TagDecl::TagKind>(kind));
   class_template_specialization_decl->setDeclContext(decl_ctx);
   class_template_specialization_decl->setInstantiationOf(class_template_decl);
   class_template_specialization_decl->setTemplateArgs(
       TemplateArgumentList::CreateCopy(ast, args));
   ast.getTypeDeclType(class_template_specialization_decl, nullptr);
   class_template_specialization_decl->setDeclName(
       class_template_decl->getDeclName());
-  // FIXME: Turning this on breaks the libcxx data formatter tests.
-  // SetOwningModule marks the Decl as external, which prevents a
-  // LookupPtr from being built. Template instantiations can also not
-  // be found by ExternalASTSource::FindExternalVisibleDeclsByName(),
-  // nor can we lazily build a LookupPtr later, because template
-  // specializations are supposed to be hidden so
-  // makeDeclVisibleInContextWithFlags() is a noop, as well.
-  //
-  // SetOwningModule(class_template_specialization_decl, owning_module);
+  SetOwningModule(class_template_specialization_decl, owning_module);
   decl_ctx->addDecl(class_template_specialization_decl);
 
   class_template_specialization_decl->setSpecializationKind(
       TSK_ExplicitSpecialization);
 
   return class_template_specialization_decl;
 }