Introduce parent ScopeState class and track the scope through the state in the parser

src/parsing/preparser.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_PARSING_PREPARSER_H
 #define V8_PARSING_PREPARSER_H
 
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
 #include "src/base/hashmap.h"
@@ skipping 1019 matching lines @@
       : ParserBase<PreParserTraits>(zone, scanner, stack_limit, NULL,
                                     ast_value_factory, log, this),
         use_counts_(nullptr) {}
 
   // Pre-parse the program from the character stream; returns true on
   // success (even if parsing failed, the pre-parse data successfully
   // captured the syntax error), and false if a stack-overflow happened
   // during parsing.
   PreParseResult PreParseProgram(int* materialized_literals = 0,
                                  bool is_module = false) {
-    Scope* scope = NewScope(scope_, SCRIPT_SCOPE);
+    DCHECK_NULL(scope_state_);
+    Scope* scope = NewScope(nullptr, SCRIPT_SCOPE);
 
     // ModuleDeclarationInstantiation for Source Text Module Records creates a
     // new Module Environment Record whose outer lexical environment record is
     // the global scope.
     if (is_module) {
       scope = NewScope(scope, MODULE_SCOPE);
     }
 
-    PreParserFactory factory(NULL);
-    FunctionState top_scope(&function_state_, &scope_, scope, kNormalFunction,
-                            &factory);
+    PreParserFactory factory(nullptr);
+    FunctionState top_scope(&function_state_, &scope_state_, scope,
+                            kNormalFunction, &factory);
     bool ok = true;
     int start_position = scanner()->peek_location().beg_pos;
     parsing_module_ = is_module;
     ParseStatementList(Token::EOS, &ok);
     if (stack_overflow()) return kPreParseStackOverflow;
     if (!ok) {
       ReportUnexpectedToken(scanner()->current_token());
-    } else if (is_strict(scope_->language_mode())) {
+    } else if (is_strict(this->scope()->language_mode())) {
       CheckStrictOctalLiteral(start_position, scanner()->location().end_pos,
                               &ok);
       CheckDecimalLiteralWithLeadingZero(use_counts_, start_position,
                                          scanner()->location().end_pos);
     }
     if (materialized_literals) {
       *materialized_literals = function_state_->materialized_literal_count();
     }
     return kPreParseSuccess;
   }
@@ skipping 168 matching lines @@
     PreParserExpression generator, PreParserExpression expression, int pos) {
   return PreParserExpression::Default();
 }
 
 PreParserStatementList PreParser::ParseEagerFunctionBody(
     PreParserIdentifier function_name, int pos,
     const PreParserFormalParameters& parameters, FunctionKind kind,
     FunctionLiteral::FunctionType function_type, bool* ok) {
   ParsingModeScope parsing_mode(this, PARSE_EAGERLY);
 
-  Scope* inner_scope = scope_;
-  if (!parameters.is_simple) inner_scope = NewScope(scope_, BLOCK_SCOPE);
+  Scope* inner_scope = scope();
+  if (!parameters.is_simple) inner_scope = NewScope(scope(), BLOCK_SCOPE);
 
   {
-    BlockState block_state(&scope_, inner_scope);
+    BlockState block_state(&scope_state_, inner_scope);
     ParseStatementList(Token::RBRACE, ok);
     if (!*ok) return PreParserStatementList();
   }
 
   Expect(Token::RBRACE, ok);
   return PreParserStatementList();
 }
 
 
 PreParserStatementList PreParserTraits::ParseEagerFunctionBody(
     PreParserIdentifier function_name, int pos,
     const PreParserFormalParameters& parameters, FunctionKind kind,
     FunctionLiteral::FunctionType function_type, bool* ok) {
   return pre_parser_->ParseEagerFunctionBody(function_name, pos, parameters,
                                              kind, function_type, ok);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PREPARSER_H