[lldb] Unify the two CreateTypedef implementations in TypeSystemClang

To get LLDB one step closer to fulfil the software redundancy requirements of
modern aircrafts, we apparently decided to have two separately maintained
implementations of `CreateTypedef` in TypeSystemClang. Let's pass on the idea of
an LLDB-powered jetliner and deleted one implementation.

On a more serious note: This function got duplicated a long time ago when the
idea of CompilerType with a backing TypeSystemClang subclass happened
(56939cb310). One implementation was supposed to
be called from CompilerType::CreateTypedef and the other has just always been
around to create typedefs. By accident one of the implementations is only used
by the PDB parser while the CompilerType::CreateTypedef backend is used by the
rest of LLDB.

We also had some patches over the year that only fixed one of the two functions
(D18099 for example only fixed up the CompilerType::CreateTypedef
implementation). D51162 and D86140 both fixed the same missing `addDecl` call
for one of the two implementations.

This patch:
* deletes the `CreateTypedefType` function as its only used by the PDB parser
  and the `CreateTypedef` implementation is anyway needed as it's the backend
  implementation of CompilerType.
* replaces the calls in the PDB parser by just calling the CompilerType wrapper.
* moves the documentation to the remaining function.
* moves the check for empty typedef names that was only in the deleted
  implementation to the other (I don't think this fixes anything as I believe
  all callers are already doing the same check).

I'll fix up the usual stuff (not using StringRef, not doing early exit) in a NFC
follow-up.

This patch is not NFC as the PDB parser now calls the function that has the fix
from D18099.

Reviewed By: labath, JDevlieghere

Differential Revision: https://reviews.llvm.org/D93382

lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.cpp

@@ -881,8 +881,8 @@ PdbAstBuilder::GetOrCreateTypedefDecl(PdbGlobalSymId id) {
 
   std::string uname = std::string(DropNameScope(udt.Name));
 
-  CompilerType ct = m_clang.CreateTypedefType(ToCompilerType(qt), uname.c_str(),
-                                              ToCompilerDeclContext(*scope), 0);
+  CompilerType ct = ToCompilerType(qt).CreateTypedef(
+      uname.c_str(), ToCompilerDeclContext(*scope), 0);
   clang::TypedefNameDecl *tnd = m_clang.GetAsTypedefDecl(ct);
   DeclStatus status;
   status.resolved = true;

lldb/source/Plugins/SymbolFile/PDB/PDBASTParser.cpp

@@ -550,8 +550,8 @@ lldb::TypeSP PDBASTParser::CreateLLDBTypeFromPDBType(const PDBSymbol &type) {
     if (!ast_typedef.IsValid()) {
       CompilerType target_ast_type = target_type->GetFullCompilerType();
 
-      ast_typedef = m_ast.CreateTypedefType(
-          target_ast_type, name.c_str(), m_ast.CreateDeclContext(decl_ctx), 0);
+      ast_typedef = target_ast_type.CreateTypedef(
+          name.c_str(), m_ast.CreateDeclContext(decl_ctx), 0);
       if (!ast_typedef)
         return nullptr;
 

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

@@ -4402,39 +4402,6 @@ TypeSystemClang::GetNonReferenceType(lldb::opaque_compiler_type_t type) {
   return CompilerType();
 }
 
-CompilerType TypeSystemClang::CreateTypedefType(
-    const CompilerType &type, const char *typedef_name,
-    const CompilerDeclContext &compiler_decl_ctx, uint32_t payload) {
-  if (type && typedef_name && typedef_name[0]) {
-    TypeSystemClang *ast =
-        llvm::dyn_cast<TypeSystemClang>(type.GetTypeSystem());
-    if (!ast)
-      return CompilerType();
-    clang::ASTContext &clang_ast = ast->getASTContext();
-    clang::QualType qual_type(ClangUtil::GetQualType(type));
-
-    clang::DeclContext *decl_ctx =
-        TypeSystemClang::DeclContextGetAsDeclContext(compiler_decl_ctx);
-    if (!decl_ctx)
-      decl_ctx = ast->getASTContext().getTranslationUnitDecl();
-
-    clang::TypedefDecl *decl =
-        clang::TypedefDecl::CreateDeserialized(clang_ast, 0);
-    decl->setDeclContext(decl_ctx);
-    decl->setDeclName(&clang_ast.Idents.get(typedef_name));
-    decl->setTypeSourceInfo(clang_ast.getTrivialTypeSourceInfo(qual_type));
-
-    SetOwningModule(decl, TypePayloadClang(payload).GetOwningModule());
-    decl->setAccess(clang::AS_public); // TODO respect proper access specifier
-
-    decl_ctx->addDecl(decl);
-
-    // Get a uniqued clang::QualType for the typedef decl type
-    return ast->GetType(clang_ast.getTypedefType(decl));
-  }
-  return CompilerType();
-}
-
 CompilerType
 TypeSystemClang::GetPointeeType(lldb::opaque_compiler_type_t type) {
   if (type) {
@@ -4516,7 +4483,7 @@ TypeSystemClang::AddRestrictModifier(lldb::opaque_compiler_type_t type) {
 CompilerType TypeSystemClang::CreateTypedef(
     lldb::opaque_compiler_type_t type, const char *typedef_name,
     const CompilerDeclContext &compiler_decl_ctx, uint32_t payload) {
-  if (type) {
+  if (type && typedef_name && typedef_name[0]) {
     clang::ASTContext &clang_ast = getASTContext();
     clang::QualType qual_type(GetQualType(type));
 
@@ -4525,10 +4492,11 @@ CompilerType TypeSystemClang::CreateTypedef(
     if (!decl_ctx)
       decl_ctx = getASTContext().getTranslationUnitDecl();
 
-    clang::TypedefDecl *decl = clang::TypedefDecl::Create(
-        clang_ast, decl_ctx, clang::SourceLocation(), clang::SourceLocation(),
-        &clang_ast.Idents.get(typedef_name),
-        clang_ast.getTrivialTypeSourceInfo(qual_type));
+    clang::TypedefDecl *decl =
+        clang::TypedefDecl::CreateDeserialized(clang_ast, 0);
+    decl->setDeclContext(decl_ctx);
+    decl->setDeclName(&clang_ast.Idents.get(typedef_name));
+    decl->setTypeSourceInfo(clang_ast.getTrivialTypeSourceInfo(qual_type));
     decl_ctx->addDecl(decl);
     SetOwningModule(decl, TypePayloadClang(payload).GetOwningModule());
 

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

@@ -665,14 +665,6 @@ public:
 
   // Creating related types
 
-  /// Using the current type, create a new typedef to that type using
-  /// "typedef_name" as the name and "decl_ctx" as the decl context.
-  /// \param opaque_payload is an opaque TypePayloadClang.
-  static CompilerType
-  CreateTypedefType(const CompilerType &type, const char *typedef_name,
-                    const CompilerDeclContext &compiler_decl_ctx,
-                    uint32_t opaque_payload);
-
   CompilerType GetArrayElementType(lldb::opaque_compiler_type_t type,
                                    ExecutionContextScope *exe_scope) override;
 
@@ -720,6 +712,9 @@ public:
 
   CompilerType AddRestrictModifier(lldb::opaque_compiler_type_t type) override;
 
+  /// Using the current type, create a new typedef to that type using
+  /// "typedef_name" as the name and "decl_ctx" as the decl context.
+  /// \param opaque_payload is an opaque TypePayloadClang.
   CompilerType CreateTypedef(lldb::opaque_compiler_type_t type,
                              const char *name,
                              const CompilerDeclContext &decl_ctx,

lldb/unittests/Symbol/TestTypeSystemClang.cpp

@@ -482,9 +482,8 @@ TEST_F(TestTypeSystemClang, TemplateArguments) {
   m_ast->CompleteTagDeclarationDefinition(type);
 
   // typedef foo<int, 47> foo_def;
-  CompilerType typedef_type = m_ast->CreateTypedefType(
-      type, "foo_def",
-      m_ast->CreateDeclContext(m_ast->GetTranslationUnitDecl()), 0);
+  CompilerType typedef_type = type.CreateTypedef(
+      "foo_def", m_ast->CreateDeclContext(m_ast->GetTranslationUnitDecl()), 0);
 
   CompilerType auto_type(
       m_ast.get(),