[NativePDB] Change GetOrCreateBlockDecl to private and introduce CreateBlockDecl

[lanza]

Summary

We're removing all clang specific details from PdbAstBuilder in order to
make it an abstract base class and then create subclasses specific to
the language.

GetOrCreateBlockDecl returns a clang::BlockDecl. But the only class that
uses the return is PdbAstBuilder itself. So we can simply create a
wrapper with no return that jumps to the actual creation block in order
to remove the clang specific behavior from PdbAstBuilder.

source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.h

public:
 
   lldb_private::CompilerDeclContext GetTranslationUnitDecl();
 
   lldb_private::CompilerDecl GetOrCreateDeclForUid(PdbSymUid uid);
   lldb_private::CompilerDeclContext GetOrCreateDeclContextForUid(PdbSymUid uid);
   lldb_private::CompilerDeclContext GetParentDeclContext(PdbSymUid uid);
 
   void CreateFunctionDecl(PdbCompilandSymId func_id);
-  clang::BlockDecl *GetOrCreateBlockDecl(PdbCompilandSymId block_id);
+  void CreateBlockDecl(PdbCompilandSymId block_id);
   clang::VarDecl *GetOrCreateVariableDecl(PdbCompilandSymId scope_id,
                                           PdbCompilandSymId var_id);
   clang::VarDecl *GetOrCreateVariableDecl(PdbGlobalSymId var_id);
   clang::TypedefNameDecl *GetOrCreateTypedefDecl(PdbGlobalSymId id);
   void ParseDeclsForContext(clang::DeclContext &context);
 
   clang::QualType GetBasicType(lldb::BasicType type);
   clang::QualType GetOrCreateType(PdbTypeSymId type);
 
   bool CompleteTagDecl(clang::TagDecl &tag);
   bool CompleteType(clang::QualType qt);
 
   CompilerDecl ToCompilerDecl(clang::Decl &decl);
   CompilerType ToCompilerType(clang::QualType qt);
   CompilerDeclContext ToCompilerDeclContext(clang::DeclContext &context);
   clang::DeclContext *FromCompilerDeclContext(CompilerDeclContext context);
 
   ClangASTContext &clang() { return m_clang; }
   ClangASTImporter &importer() { return m_importer; }
 
   void Dump(Stream &stream);
 
 private:
   clang::FunctionDecl *GetOrCreateFunctionDecl(PdbCompilandSymId func_id);
+  clang::BlockDecl *GetOrCreateBlockDecl(PdbCompilandSymId block_id);
 
   clang::Decl *TryGetDecl(PdbSymUid uid) const;
 
   using TypeIndex = llvm::codeview::TypeIndex;
 
   clang::QualType
   CreatePointerType(const llvm::codeview::PointerRecord &pointer);
   clang::QualType

source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.cpp

 
 clang::NamespaceDecl *
 PdbAstBuilder::GetOrCreateNamespaceDecl(const char *name,
                                         clang::DeclContext &context) {
   return m_clang.GetUniqueNamespaceDeclaration(
       IsAnonymousNamespaceName(name) ? nullptr : name, &context);
 }
 
+void PdbAstBuilder::CreateBlockDecl(PdbCompilandSymId block_id) {
+  GetOrCreateBlockDecl(block_id);
+}
+
 clang::BlockDecl *
 PdbAstBuilder::GetOrCreateBlockDecl(PdbCompilandSymId block_id) {
   if (clang::Decl *decl = TryGetDecl(block_id))
     return llvm::dyn_cast<clang::BlockDecl>(decl);
 
   lldb_private::CompilerDeclContext decl_ctx = GetParentDeclContext(block_id);
   auto scope =
       static_cast<clang::DeclContext *>(decl_ctx.GetOpaqueDeclContext());

source/Plugins/SymbolFile/NativePDB/SymbolFileNativePDB.cpp

Block &SymbolFileNativePDB::CreateBlock(PdbCompilandSymId block_id) {
   cantFail(SymbolDeserializer::deserializeAs<BlockSym>(sym, block));
   lldbassert(block.Parent != 0);
   PdbCompilandSymId parent_id(block_id.modi, block.Parent);
   Block &parent_block = GetOrCreateBlock(parent_id);
   lldb::user_id_t opaque_block_uid = toOpaqueUid(block_id);
   BlockSP child_block = std::make_shared<Block>(opaque_block_uid);
   parent_block.AddChild(child_block);
 
-  m_ast->GetOrCreateBlockDecl(block_id);
+  m_ast->CreateBlockDecl(block_id);
 
   m_blocks.insert({opaque_block_uid, child_block});
   return *child_block;
 }
 
 lldb::FunctionSP SymbolFileNativePDB::CreateFunction(PdbCompilandSymId func_id,
                                                      CompileUnit &comp_unit) {
   const CompilandIndexItem *cci =