Add initial parser support for harmony iteration

src/parser.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 533 matching lines @@
       reusable_preparser_(NULL),
       top_scope_(NULL),
       current_function_state_(NULL),
       target_stack_(NULL),
       extension_(info->extension()),
       pre_parse_data_(NULL),
       fni_(NULL),
       allow_natives_syntax_(false),
       allow_lazy_(false),
       allow_generators_(false),
+      allow_for_of_(false),
       stack_overflow_(false),
       parenthesized_function_(false),
       zone_(info->zone()),
       info_(info) {
   ASSERT(!script_.is_null());
   isolate_->set_ast_node_id(0);
   set_allow_harmony_scoping(!info->is_native() && FLAG_harmony_scoping);
   set_allow_modules(!info->is_native() && FLAG_harmony_modules);
   set_allow_natives_syntax(FLAG_allow_natives_syntax || info->is_native());
   set_allow_lazy(false);  // Must be explicitly enabled.
   set_allow_generators(FLAG_harmony_generators);
+  set_allow_for_of(FLAG_harmony_iteration);
 }
 
 
 FunctionLiteral* Parser::ParseProgram() {
   ZoneScope zone_scope(zone(), DONT_DELETE_ON_EXIT);
   HistogramTimerScope timer(isolate()->counters()->parse());
   Handle<String> source(String::cast(script_->source()));
   isolate()->counters()->total_parse_size()->Increment(source->length());
   int64_t start = FLAG_trace_parse ? OS::Ticks() : 0;
   fni_ = new(zone()) FuncNameInferrer(isolate(), zone());
@@ skipping 640 matching lines @@
       return ParseModuleLiteral(ok);
 
     case Token::ASSIGN: {
       Expect(Token::ASSIGN, CHECK_OK);
       Module* result = ParseModulePath(CHECK_OK);
       ExpectSemicolon(CHECK_OK);
       return result;
     }
 
     default: {
-      ExpectContextualKeyword("at", CHECK_OK);
+      ExpectContextualKeyword(CStrVector("at"), CHECK_OK);
       Module* result = ParseModuleUrl(CHECK_OK);
       ExpectSemicolon(CHECK_OK);
       return result;
     }
   }
 }
 
 
 Module* Parser::ParseModuleLiteral(bool* ok) {
   // Module:
@@ skipping 151 matching lines @@
   ZoneStringList names(1, zone());
 
   Handle<String> name = ParseIdentifierName(CHECK_OK);
   names.Add(name, zone());
   while (peek() == Token::COMMA) {
     Consume(Token::COMMA);
     name = ParseIdentifierName(CHECK_OK);
     names.Add(name, zone());
   }
 
-  ExpectContextualKeyword("from", CHECK_OK);
+  ExpectContextualKeyword(CStrVector("from"), CHECK_OK);
   Module* module = ParseModuleSpecifier(CHECK_OK);
   ExpectSemicolon(CHECK_OK);
 
   // Generate a separate declaration for each identifier.
   // TODO(ES6): once we implement destructuring, make that one declaration.
   Block* block = factory()->NewBlock(NULL, 1, true);
   for (int i = 0; i < names.length(); ++i) {
 #ifdef DEBUG
     if (FLAG_print_interface_details)
       PrintF("# Import %s ", names[i]->ToAsciiArray());
@@ skipping 1400 matching lines @@
   Expect(Token::LPAREN, CHECK_OK);
   Expression* cond = ParseExpression(true, CHECK_OK);
   Expect(Token::RPAREN, CHECK_OK);
   Statement* body = ParseStatement(NULL, CHECK_OK);
 
   if (loop != NULL) loop->Initialize(cond, body);
   return loop;
 }
 
 
+bool Parser::CheckInOrOf(ForEachStatement::VisitMode* visit_mode) {
+  if (Check(Token::IN)) {
+    *visit_mode = ForEachStatement::ENUMERATE;
+    return true;
+  } else if (FLAG_harmony_iteration &&
+             CheckContextualKeyword(CStrVector("of"))) {
+    *visit_mode = ForEachStatement::ITERATE;
+    return true;
+  }
+  return false;
+}
+
+
 Statement* Parser::ParseForStatement(ZoneStringList* labels, bool* ok) {
   // ForStatement ::
   //   'for' '(' Expression? ';' Expression? ';' Expression? ')' Statement
 
   Statement* init = NULL;
 
   // Create an in-between scope for let-bound iteration variables.
   Scope* saved_scope = top_scope_;
   Scope* for_scope = NewScope(top_scope_, BLOCK_SCOPE);
   top_scope_ = for_scope;
 
   Expect(Token::FOR, CHECK_OK);
   Expect(Token::LPAREN, CHECK_OK);
   for_scope->set_start_position(scanner().location().beg_pos);
   if (peek() != Token::SEMICOLON) {
     if (peek() == Token::VAR || peek() == Token::CONST) {
       bool is_const = peek() == Token::CONST;
       Handle<String> name;
       Block* variable_statement =
           ParseVariableDeclarations(kForStatement, NULL, NULL, &name, CHECK_OK);
+      ForEachStatement::VisitMode mode;
 
-      if (peek() == Token::IN && !name.is_null()) {
+      if (!name.is_null() && CheckInOrOf(&mode)) {
         Interface* interface =
             is_const ? Interface::NewConst() : Interface::NewValue();
-        ForInStatement* loop = factory()->NewForInStatement(labels);
+        ForEachStatement* loop = factory()->NewForEachStatement(mode, labels);
         Target target(&this->target_stack_, loop);
 
-        Expect(Token::IN, CHECK_OK);
         Expression* enumerable = ParseExpression(true, CHECK_OK);
         Expect(Token::RPAREN, CHECK_OK);
 
         VariableProxy* each =
             top_scope_->NewUnresolved(factory(), name, interface);
         Statement* body = ParseStatement(NULL, CHECK_OK);
         loop->Initialize(each, enumerable, body);
         Block* result = factory()->NewBlock(NULL, 2, false);
         result->AddStatement(variable_statement, zone());
         result->AddStatement(loop, zone());
         top_scope_ = saved_scope;
         for_scope->set_end_position(scanner().location().end_pos);
         for_scope = for_scope->FinalizeBlockScope();
         ASSERT(for_scope == NULL);
         // Parsed for-in loop w/ variable/const declaration.
         return result;
       } else {
         init = variable_statement;
       }
     } else if (peek() == Token::LET) {
       Handle<String> name;
       VariableDeclarationProperties decl_props = kHasNoInitializers;
       Block* variable_statement =
          ParseVariableDeclarations(kForStatement, &decl_props, NULL, &name,
                                    CHECK_OK);
       bool accept_IN = !name.is_null() && decl_props != kHasInitializers;
-      if (peek() == Token::IN && accept_IN) {
+      ForEachStatement::VisitMode mode;
+
+      if (accept_IN && CheckInOrOf(&mode)) {
         // Rewrite a for-in statement of the form
         //
         //   for (let x in e) b
         //
         // into
         //
         //   <let x' be a temporary variable>
         //   for (x' in e) {
         //     let x;
         //     x = x';
         //     b;
         //   }
 
         // TODO(keuchel): Move the temporary variable to the block scope, after
         // implementing stack allocated block scoped variables.
         Factory* heap_factory = isolate()->factory();
         Handle<String> tempstr =
             heap_factory->NewConsString(heap_factory->dot_for_string(), name);
         Handle<String> tempname = heap_factory->InternalizeString(tempstr);
         Variable* temp = top_scope_->DeclarationScope()->NewTemporary(tempname);
         VariableProxy* temp_proxy = factory()->NewVariableProxy(temp);
-        ForInStatement* loop = factory()->NewForInStatement(labels);
+        ForEachStatement* loop = factory()->NewForEachStatement(mode, labels);
         Target target(&this->target_stack_, loop);
 
         // The expression does not see the loop variable.
-        Expect(Token::IN, CHECK_OK);
         top_scope_ = saved_scope;
         Expression* enumerable = ParseExpression(true, CHECK_OK);
         top_scope_ = for_scope;
         Expect(Token::RPAREN, CHECK_OK);
 
         VariableProxy* each =
             top_scope_->NewUnresolved(factory(), name, Interface::NewValue());
         Statement* body = ParseStatement(NULL, CHECK_OK);
         Block* body_block = factory()->NewBlock(NULL, 3, false);
         Assignment* assignment = factory()->NewAssignment(
             Token::ASSIGN, each, temp_proxy, RelocInfo::kNoPosition);
         Statement* assignment_statement =
             factory()->NewExpressionStatement(assignment);
         body_block->AddStatement(variable_statement, zone());
         body_block->AddStatement(assignment_statement, zone());
         body_block->AddStatement(body, zone());
         loop->Initialize(temp_proxy, enumerable, body_block);
         top_scope_ = saved_scope;
         for_scope->set_end_position(scanner().location().end_pos);
         for_scope = for_scope->FinalizeBlockScope();
         body_block->set_scope(for_scope);
         // Parsed for-in loop w/ let declaration.
         return loop;
 
       } else {
         init = variable_statement;
       }
     } else {
       Expression* expression = ParseExpression(false, CHECK_OK);
-      if (peek() == Token::IN) {
+      ForEachStatement::VisitMode mode;
+
+      if (CheckInOrOf(&mode)) {
         // Signal a reference error if the expression is an invalid
         // left-hand side expression.  We could report this as a syntax
         // error here but for compatibility with JSC we choose to report
         // the error at runtime.
         if (expression == NULL || !expression->IsValidLeftHandSide()) {
           Handle<String> type =
               isolate()->factory()->invalid_lhs_in_for_in_string();
           expression = NewThrowReferenceError(type);
         }
-        ForInStatement* loop = factory()->NewForInStatement(labels);
+        ForEachStatement* loop = factory()->NewForEachStatement(mode, labels);
         Target target(&this->target_stack_, loop);
 
-        Expect(Token::IN, CHECK_OK);
         Expression* enumerable = ParseExpression(true, CHECK_OK);
         Expect(Token::RPAREN, CHECK_OK);
 
         Statement* body = ParseStatement(NULL, CHECK_OK);
-        if (loop) loop->Initialize(expression, enumerable, body);

[rossberg, 2013/06/06 10:32:33]

Weird, what was the purpose of this condition?

[wingo, 2013/06/06 14:09:51]

I... I don't know!  I think this is another vestige from an earlier patch, but
I'm almost certain it's correct.  The factory constructor cannot possibly return
a non-null value.  Likewise there are null checks later in the function for
normal For; I'll remove those in the next patch.  This code was present in the
initial V8 import in 2008.

+        loop->Initialize(expression, enumerable, body);
         top_scope_ = saved_scope;
         for_scope->set_end_position(scanner().location().end_pos);
         for_scope = for_scope->FinalizeBlockScope();
         ASSERT(for_scope == NULL);
         // Parsed for-in loop.
         return loop;
 
       } else {
         init = factory()->NewExpressionStatement(expression);
       }
@@ skipping 1742 matching lines @@
   if (reusable_preparser_ == NULL) {
     intptr_t stack_limit = isolate()->stack_guard()->real_climit();
     reusable_preparser_ = new preparser::PreParser(&scanner_,
                                                    NULL,
                                                    stack_limit);
     reusable_preparser_->set_allow_harmony_scoping(allow_harmony_scoping());
     reusable_preparser_->set_allow_modules(allow_modules());
     reusable_preparser_->set_allow_natives_syntax(allow_natives_syntax());
     reusable_preparser_->set_allow_lazy(true);
     reusable_preparser_->set_allow_generators(allow_generators());
+    reusable_preparser_->set_allow_for_of(allow_for_of());
   }
   preparser::PreParser::PreParseResult result =
       reusable_preparser_->PreParseLazyFunction(top_scope_->language_mode(),
                                                 is_generator(),
                                                 logger);
   return result;
 }
 
 
 Expression* Parser::ParseV8Intrinsic(bool* ok) {
@@ skipping 77 matching lines @@
 bool Parser::Check(Token::Value token) {
   Token::Value next = peek();
   if (next == token) {
     Consume(next);
     return true;
   }
   return false;
 }
 
 
+bool Parser::CheckContextualKeyword(Vector<const char> keyword) {
+  if (peek() == Token::IDENTIFIER &&
+      scanner().is_next_contextual_keyword(keyword)) {
+    Consume(Token::IDENTIFIER);
+    return true;
+  }
+  return false;
+}
+
+
 void Parser::ExpectSemicolon(bool* ok) {
   // Check for automatic semicolon insertion according to
   // the rules given in ECMA-262, section 7.9, page 21.
   Token::Value tok = peek();
   if (tok == Token::SEMICOLON) {
     Next();
     return;
   }
   if (scanner().HasAnyLineTerminatorBeforeNext() ||
       tok == Token::RBRACE ||
       tok == Token::EOS) {
     return;
   }
   Expect(Token::SEMICOLON, ok);
 }
 
 
-void Parser::ExpectContextualKeyword(const char* keyword, bool* ok) {
+void Parser::ExpectContextualKeyword(Vector<const char> keyword, bool* ok) {
   Expect(Token::IDENTIFIER, ok);
   if (!*ok) return;
-  Handle<String> symbol = GetSymbol(ok);
-  if (!*ok) return;
-  if (!symbol->IsUtf8EqualTo(CStrVector(keyword))) {
+  if (!scanner().is_literal_contextual_keyword(keyword)) {
     *ok = false;
     ReportUnexpectedToken(scanner().current_token());
   }
 }
 
 
 Literal* Parser::GetLiteralUndefined() {
   return factory()->NewLiteral(isolate()->factory()->undefined_value());
 }
 
@@ skipping 1115 matching lines @@
 // Create a Scanner for the preparser to use as input, and preparse the source.
 ScriptDataImpl* PreParserApi::PreParse(Utf16CharacterStream* source) {
   CompleteParserRecorder recorder;
   Isolate* isolate = Isolate::Current();
   HistogramTimerScope timer(isolate->counters()->pre_parse());
   Scanner scanner(isolate->unicode_cache());
   intptr_t stack_limit = isolate->stack_guard()->real_climit();
   preparser::PreParser preparser(&scanner, &recorder, stack_limit);
   preparser.set_allow_lazy(true);
   preparser.set_allow_generators(FLAG_harmony_generators);
+  preparser.set_allow_for_of(FLAG_harmony_iteration);
   preparser.set_allow_harmony_scoping(FLAG_harmony_scoping);
   scanner.Initialize(source);
   preparser::PreParser::PreParseResult result = preparser.PreParseProgram();
   if (result == preparser::PreParser::kPreParseStackOverflow) {
     isolate->StackOverflow();
     return NULL;
   }
 
   // Extract the accumulated data from the recorder as a single
   // contiguous vector that we are responsible for disposing.
@@ skipping 51 matching lines @@
       ASSERT(info()->isolate()->has_pending_exception());
     } else {
       result = ParseProgram();
     }
   }
   info()->SetFunction(result);
   return (result != NULL);
 }
 
 } }  // namespace v8::internal