[lldb][NFC] Make CompilerDeclContext construction type safe

The CompilerDeclContext constructor takes a void* pointer which
means that all callers of this constructor need to first explicitly
convert all pointers to clang::DeclContext*. This causes that we
for example can't just pass a TranslationUnitDecl* to the constructor without
first casting it to its parent class (as it inherits from both
Decl and DeclContext so the void* pointer is actually a Decl*).

This patch introduces a utility function in the ClangASTContext
which gets rid of the requirement to cast all pointers to
clang::DeclContext. Also moves all constructor calls to use this
function instead which is NFC (beside the change in
DWARFASTParserClangTests.cpp).

lldb/include/lldb/Symbol/ClangASTContext.h

@@ -440,6 +440,12 @@ public:
 
   // CompilerDeclContext override functions
 
+  /// Creates a CompilerDeclContext from the given DeclContext
+  /// with the current ClangASTContext instance as its typesystem.
+  /// The DeclContext has to come from the ASTContext of this
+  /// ClangASTContext.
+  CompilerDeclContext CreateDeclContext(clang::DeclContext *ctx);
+
   std::vector<CompilerDecl>
   DeclContextFindDeclByName(void *opaque_decl_ctx, ConstString name,
                             const bool ignore_using_decls) override;

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp

@@ -682,9 +682,7 @@ void ClangExpressionDeclMap::FindExternalVisibleDecls(
           dyn_cast<NamespaceDecl>(context.m_decl_context)) {
     if (namespace_context->getName().str() ==
         std::string(g_lldb_local_vars_namespace_cstr)) {
-      CompilerDeclContext compiler_decl_ctx(
+      CompilerDeclContext compiler_decl_ctx = GetClangASTContext()->CreateDeclContext(const_cast<clang::DeclContext*>(context.m_decl_context));
-          GetClangASTContext(), const_cast<void *>(static_cast<const void *>(
-                                    context.m_decl_context)));
       FindExternalVisibleDecls(context, lldb::ModuleSP(), compiler_decl_ctx,
                                current_id);
       return;

lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp

@@ -2218,7 +2218,7 @@ CompilerDeclContext
 DWARFASTParserClang::GetDeclContextForUIDFromDWARF(const DWARFDIE &die) {
   clang::DeclContext *clang_decl_ctx = GetClangDeclContextForDIE(die);
   if (clang_decl_ctx)
-    return CompilerDeclContext(&m_ast, clang_decl_ctx);
+    return m_ast.CreateDeclContext(clang_decl_ctx);
   return CompilerDeclContext();
 }
 
@@ -2227,7 +2227,7 @@ DWARFASTParserClang::GetDeclContextContainingUIDFromDWARF(const DWARFDIE &die) {
   clang::DeclContext *clang_decl_ctx =
       GetClangDeclContextContainingDIE(die, nullptr);
   if (clang_decl_ctx)
-    return CompilerDeclContext(&m_ast, clang_decl_ctx);
+    return m_ast.CreateDeclContext(clang_decl_ctx);
   return CompilerDeclContext();
 }
 

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

@@ -1343,7 +1343,7 @@ CompilerType PdbAstBuilder::ToCompilerType(clang::QualType qt) {
 
 CompilerDeclContext
 PdbAstBuilder::ToCompilerDeclContext(clang::DeclContext &context) {
-  return {&m_clang, &context};
+  return m_clang.CreateDeclContext(&context);
 }
 
 clang::Decl * PdbAstBuilder::FromCompilerDecl(CompilerDecl decl) {

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

@@ -556,7 +556,7 @@ lldb::TypeSP PDBASTParser::CreateLLDBTypeFromPDBType(const PDBSymbol &type) {
       CompilerType target_ast_type = target_type->GetFullCompilerType();
 
       ast_typedef = m_ast.CreateTypedefType(
-          target_ast_type, name.c_str(), CompilerDeclContext(&m_ast, decl_ctx));
+          target_ast_type, name.c_str(), m_ast.CreateDeclContext(decl_ctx));
       if (!ast_typedef)
         return nullptr;
 

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

@@ -666,7 +666,7 @@ SymbolFilePDB::GetDeclContextForUID(lldb::user_id_t uid) {
   if (!decl_context)
     return GetDeclContextContainingUID(uid);
 
-  return CompilerDeclContext(clang_ast_ctx, decl_context);
+  return clang_ast_ctx->CreateDeclContext(decl_context);
 }
 
 lldb_private::CompilerDeclContext
@@ -695,7 +695,7 @@ SymbolFilePDB::GetDeclContextContainingUID(lldb::user_id_t uid) {
   auto decl_context = pdb->GetDeclContextContainingSymbol(*symbol);
   assert(decl_context);
 
-  return CompilerDeclContext(clang_ast_ctx, decl_context);
+  return clang_ast_ctx->CreateDeclContext(decl_context);
 }
 
 void SymbolFilePDB::ParseDeclsForContext(
@@ -1703,8 +1703,7 @@ lldb_private::CompilerDeclContext SymbolFilePDB::FindNamespace(
   if (!namespace_decl)
     return CompilerDeclContext();
 
-  return CompilerDeclContext(clang_type_system,
+  return clang_type_system->CreateDeclContext(namespace_decl);
-                             static_cast<clang::DeclContext *>(namespace_decl));
 }
 
 lldb_private::ConstString SymbolFilePDB::GetPluginName() {

lldb/source/Symbol/ClangASTContext.cpp

@@ -1205,9 +1205,13 @@ CompilerType ClangASTContext::GetTypeForDecl(void *opaque_decl) {
   return CompilerType();
 }
 
+CompilerDeclContext ClangASTContext::CreateDeclContext(DeclContext *ctx) {
+  return CompilerDeclContext(this, ctx);
+}
+
 CompilerType ClangASTContext::GetTypeForDecl(clang::NamedDecl *decl) {
   if (clang::ObjCInterfaceDecl *interface_decl =
-          llvm::dyn_cast<clang::ObjCInterfaceDecl>(decl))
+      llvm::dyn_cast<clang::ObjCInterfaceDecl>(decl))
     return GetTypeForDecl(interface_decl);
   if (clang::TagDecl *tag_decl = llvm::dyn_cast<clang::TagDecl>(decl))
     return GetTypeForDecl(tag_decl);
@@ -9039,10 +9043,8 @@ ConstString ClangASTContext::DeclGetMangledName(void *opaque_decl) {
 
 CompilerDeclContext ClangASTContext::DeclGetDeclContext(void *opaque_decl) {
   if (opaque_decl)
-    return CompilerDeclContext(this,
+    return CreateDeclContext(((clang::Decl *)opaque_decl)->getDeclContext());
-                               ((clang::Decl *)opaque_decl)->getDeclContext());
+  return CompilerDeclContext();
-  else
-    return CompilerDeclContext();
 }
 
 CompilerType ClangASTContext::DeclGetFunctionReturnType(void *opaque_decl) {
@@ -9108,7 +9110,7 @@ std::vector<CompilerDecl> ClangASTContext::DeclContextFindDeclByName(
         if (!searched.insert(it->second).second)
           continue;
         symbol_file->ParseDeclsForContext(
-            CompilerDeclContext(this, it->second));
+            CreateDeclContext(it->second));
 
         for (clang::Decl *child : it->second->decls()) {
           if (clang::UsingDirectiveDecl *ud =
@@ -9223,7 +9225,7 @@ uint32_t ClangASTContext::CountDeclLevels(clang::DeclContext *frame_decl_ctx,
 
         searched.insert(it->second);
         symbol_file->ParseDeclsForContext(
-            CompilerDeclContext(this, it->second));
+            CreateDeclContext(it->second));
 
         for (clang::Decl *child : it->second->decls()) {
           if (clang::UsingDirectiveDecl *ud =

lldb/unittests/Symbol/TestClangASTContext.cpp

@@ -414,8 +414,7 @@ TEST_F(TestClangASTContext, TemplateArguments) {
 
   // typedef foo<int, 47> foo_def;
   CompilerType typedef_type = m_ast->CreateTypedefType(
-      type, "foo_def",
+      type, "foo_def", m_ast->CreateDeclContext(m_ast->GetTranslationUnitDecl()));
-      CompilerDeclContext(m_ast.get(), m_ast->GetTranslationUnitDecl()));
 
   CompilerType auto_type(
       m_ast.get(),

lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp

@@ -61,7 +61,7 @@ TEST_F(DWARFASTParserClangTests,
   for (int i = 0; i < 4; ++i)
     ast_parser.LinkDeclContextToDIE(decl_ctxs[i], dies[i]);
   ast_parser.EnsureAllDIEsInDeclContextHaveBeenParsed(
-      CompilerDeclContext(nullptr, decl_ctxs[1]));
+      ast_ctx.CreateDeclContext(decl_ctxs[1]));
 
   EXPECT_THAT(ast_parser.GetDeclContextToDIEMapKeys(),
               testing::UnorderedElementsAre(decl_ctxs[0], decl_ctxs[3]));