[esnext] implement frontend changes for async/await proposal

src/parsing/parser.cc

 // 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.
 
 #include "src/parsing/parser.h"
 
 #include "src/api.h"
 #include "src/ast/ast.h"
 #include "src/ast/ast-expression-rewriter.h"
 #include "src/ast/ast-expression-visitor.h"
@@ skipping 312 matching lines @@
 
 
 bool ParserTraits::IsEvalOrArguments(const AstRawString* identifier) const {
   return IsEval(identifier) || IsArguments(identifier);
 }
 
 bool ParserTraits::IsUndefined(const AstRawString* identifier) const {
   return identifier == parser_->ast_value_factory()->undefined_string();
 }
 
+bool ParserTraits::IsAwait(const AstRawString* identifier) const {
+  return identifier == parser_->ast_value_factory()->await_string();
+}
+
 bool ParserTraits::IsPrototype(const AstRawString* identifier) const {
   return identifier == parser_->ast_value_factory()->prototype_string();
 }
 
 
 bool ParserTraits::IsConstructor(const AstRawString* identifier) const {
   return identifier == parser_->ast_value_factory()->constructor_string();
 }
 
 
@@ skipping 448 matching lines @@
   set_allow_tailcalls(FLAG_harmony_tailcalls && !info->is_native() &&
                       info->isolate()->is_tail_call_elimination_enabled());
   set_allow_harmony_do_expressions(FLAG_harmony_do_expressions);
   set_allow_harmony_for_in(FLAG_harmony_for_in);
   set_allow_harmony_function_name(FLAG_harmony_function_name);
   set_allow_harmony_function_sent(FLAG_harmony_function_sent);
   set_allow_harmony_restrictive_declarations(
       FLAG_harmony_restrictive_declarations);
   set_allow_harmony_exponentiation_operator(
       FLAG_harmony_exponentiation_operator);
+  set_allow_harmony_async_await(FLAG_harmony_async_await);
   for (int feature = 0; feature < v8::Isolate::kUseCounterFeatureCount;
        ++feature) {
     use_counts_[feature] = 0;
   }
   if (info->ast_value_factory() == NULL) {
     // info takes ownership of AstValueFactory.
     info->set_ast_value_factory(new AstValueFactory(zone(), info->hash_seed()));
     info->set_ast_value_factory_owned();
     ast_value_factory_ = info->ast_value_factory();
   }
@@ skipping 257 matching lines @@
     FunctionState function_state(&function_state_, &scope_, scope,
                                  shared_info->kind(), &function_factory);
     DCHECK(is_sloppy(scope->language_mode()) ||
            is_strict(info->language_mode()));
     DCHECK(info->language_mode() == shared_info->language_mode());
     FunctionLiteral::FunctionType function_type =
         ComputeFunctionType(shared_info);
     bool ok = true;
 
     if (shared_info->is_arrow()) {
+      bool is_async = allow_harmony_async_await() && shared_info->is_async();
+      if (is_async) {
+        DCHECK(!scanner()->HasAnyLineTerminatorAfterNext());
+        Consume(Token::ASYNC);
+        DCHECK(peek_any_identifier() || peek() == Token::LPAREN);
+      }
+
       // TODO(adamk): We should construct this scope from the ScopeInfo.
       Scope* scope =
           NewScope(scope_, FUNCTION_SCOPE, FunctionKind::kArrowFunction);
 
       // These two bits only need to be explicitly set because we're
       // not passing the ScopeInfo to the Scope constructor.
       // TODO(adamk): Remove these calls once the above NewScope call
       // passes the ScopeInfo.
       if (shared_info->scope_info()->CallsEval()) {
         scope->RecordEvalCall();
@@ skipping 20 matching lines @@
             DeclareFormalParameter(formals.scope, formals.at(0),
                                    &formals_classifier);
           }
         }
       }
 
       if (ok) {
         checkpoint.Restore(&formals.materialized_literals_count);
         // Pass `accept_IN=true` to ParseArrowFunctionLiteral --- This should
         // not be observable, or else the preparser would have failed.
-        Expression* expression =
-            ParseArrowFunctionLiteral(true, formals, formals_classifier, &ok);
+        Expression* expression = ParseArrowFunctionLiteral(
+            true, formals, is_async, formals_classifier, &ok);
         if (ok) {
           // Scanning must end at the same position that was recorded
           // previously. If not, parsing has been interrupted due to a stack
           // overflow, at which point the partially parsed arrow function
           // concise body happens to be a valid expression. This is a problem
           // only for arrow functions with single expression bodies, since there
           // is no end token such as "}" for normal functions.
           if (scanner()->location().end_pos == shared_info->end_position()) {
             // The pre-parser saw an arrow function here, so the full parser
             // must produce a FunctionLiteral.
@@ skipping 118 matching lines @@
 
   return 0;
 }
 
 
 Statement* Parser::ParseStatementListItem(bool* ok) {
   // (Ecma 262 6th Edition, 13.1):
   // StatementListItem:
   //    Statement
   //    Declaration
-
-  switch (peek()) {
+  const Token::Value peeked = peek();
+  switch (peeked) {
     case Token::FUNCTION:
       return ParseHoistableDeclaration(NULL, ok);
     case Token::CLASS:
       Consume(Token::CLASS);
       return ParseClassDeclaration(NULL, ok);
     case Token::CONST:
       return ParseVariableStatement(kStatementListItem, NULL, ok);
     case Token::VAR:
       return ParseVariableStatement(kStatementListItem, NULL, ok);
     case Token::LET:
       if (IsNextLetKeyword()) {
         return ParseVariableStatement(kStatementListItem, NULL, ok);
       }
       break;
+    case Token::ASYNC:
+      if (allow_harmony_async_await() && PeekAhead() == Token::FUNCTION &&
+          !scanner()->HasAnyLineTerminatorAfterNext()) {
+        Consume(Token::ASYNC);
+        return ParseAsyncFunctionDeclaration(NULL, ok);
+      }
+    /* falls through */
     default:
       break;
   }
   return ParseStatement(NULL, kAllowLabelledFunctionStatement, ok);
 }
 
 
 Statement* Parser::ParseModuleItem(bool* ok) {
   // (Ecma 262 6th Edition, 15.2):
   // ModuleItem :
@@ skipping 269 matching lines @@
         // GeneratorDeclaration[+Default] ::
         //   'function' '*' '(' FormalParameters ')' '{' FunctionBody '}'
         default_export = ParseFunctionLiteral(
             default_string, Scanner::Location::invalid(),
             kSkipFunctionNameCheck,
             is_generator ? FunctionKind::kGeneratorFunction
                          : FunctionKind::kNormalFunction,
             pos, FunctionLiteral::kDeclaration, language_mode(), CHECK_OK);
         result = factory()->NewEmptyStatement(RelocInfo::kNoPosition);
       } else {
-        result = ParseHoistableDeclaration(pos, is_generator, &names, CHECK_OK);
+        result = ParseHoistableDeclaration(
+            pos, is_generator ? ParseFunctionFlags::kIsGenerator
+                              : ParseFunctionFlags::kIsNormal,
+            &names, CHECK_OK);
       }
       break;
     }
 
     case Token::CLASS:
       Consume(Token::CLASS);
       if (peek() == Token::EXTENDS || peek() == Token::LBRACE) {
         // ClassDeclaration[+Default] ::
         //   'class' ('extends' LeftHandExpression)? '{' ClassBody '}'
         default_export = ParseClassLiteral(nullptr, default_string,
                                            Scanner::Location::invalid(), false,
                                            position(), CHECK_OK);
         result = factory()->NewEmptyStatement(RelocInfo::kNoPosition);
       } else {
         result = ParseClassDeclaration(&names, CHECK_OK);
       }
       break;
 
+    case Token::ASYNC:
+      if (allow_harmony_async_await() && PeekAhead() == Token::FUNCTION &&
+          !scanner()->HasAnyLineTerminatorAfterNext()) {
+        Consume(Token::ASYNC);
+        Consume(Token::FUNCTION);
+        int pos = position();
+        if (peek() == Token::LPAREN) {
+          // AsyncFunctionDeclaration[+Default] ::
+          //   async [no LineTerminator here] function ( FormalParameters ) {
+          //      AsyncFunctionBody
+          //   }
+          default_export = ParseFunctionLiteral(
+              default_string, Scanner::Location::invalid(),
+              kSkipFunctionNameCheck, FunctionKind::kAsyncFunction, pos,
+              FunctionLiteral::kDeclaration, language_mode(), CHECK_OK);
+          result = factory()->NewEmptyStatement(RelocInfo::kNoPosition);
+        } else {
+          result = ParseHoistableDeclaration(pos, ParseFunctionFlags::kIsAsync,
+                                             &names, CHECK_OK);
+        }
+        break;
+      }
+    /* falls through */
+
     default: {
       int pos = peek_position();
       ExpressionClassifier classifier(this);
       Expression* expr = ParseAssignmentExpression(true, &classifier, CHECK_OK);
       RewriteNonPattern(&classifier, CHECK_OK);
 
       ExpectSemicolon(CHECK_OK);
       result = factory()->NewExpressionStatement(expr, pos);
       break;
     }
@@ skipping 104 matching lines @@
       Consume(Token::CLASS);
       result = ParseClassDeclaration(&names, CHECK_OK);
       break;
 
     case Token::VAR:
     case Token::LET:
     case Token::CONST:
       result = ParseVariableStatement(kStatementListItem, &names, CHECK_OK);
       break;
 
+    case Token::ASYNC:
+      if (allow_harmony_async_await()) {
+        Consume(Token::ASYNC);
+        result = ParseAsyncFunctionDeclaration(&names, CHECK_OK);
+        break;
+      }
+    /* falls through */
+
     default:
       *ok = false;
       ReportUnexpectedToken(scanner()->current_token());
       return NULL;
   }
 
   // Extract declared names into export declarations.
   ModuleDescriptor* descriptor = scope_->module();
   for (int i = 0; i < names.length(); ++i) {
     descriptor->AddLocalExport(names[i], names[i], zone(), ok);
@@ skipping 339 matching lines @@
   return factory()->NewExpressionStatement(
       factory()->NewAssignment(Token::INIT, proxy, lit, RelocInfo::kNoPosition),
       pos);
 }
 
 
 Statement* Parser::ParseHoistableDeclaration(
     ZoneList<const AstRawString*>* names, bool* ok) {
   Expect(Token::FUNCTION, CHECK_OK);
   int pos = position();
-  bool is_generator = Check(Token::MUL);
-  return ParseHoistableDeclaration(pos, is_generator, names, ok);
+  ParseFunctionFlags flags = ParseFunctionFlags::kIsNormal;
+  if (Check(Token::MUL)) {
+    flags |= ParseFunctionFlags::kIsGenerator;
+  }
+  return ParseHoistableDeclaration(pos, flags, names, ok);
 }
 
+Statement* Parser::ParseAsyncFunctionDeclaration(
+    ZoneList<const AstRawString*>* names, bool* ok) {
+  DCHECK_EQ(scanner()->current_token(), Token::ASYNC);
+  int pos = position();
+  if (scanner()->HasAnyLineTerminatorBeforeNext()) {
+    *ok = false;
+    ReportUnexpectedToken(scanner()->current_token());
+    return nullptr;
+  }
+  Expect(Token::FUNCTION, CHECK_OK);
+  ParseFunctionFlags flags = ParseFunctionFlags::kIsAsync;
+  return ParseHoistableDeclaration(pos, flags, names, ok);
+}
 
 Statement* Parser::ParseHoistableDeclaration(
-    int pos, bool is_generator, ZoneList<const AstRawString*>* names,
+    int pos, ParseFunctionFlags flags, ZoneList<const AstRawString*>* names,
     bool* ok) {
   // FunctionDeclaration ::
   //   'function' Identifier '(' FormalParameters ')' '{' FunctionBody '}'
   // GeneratorDeclaration ::
   //   'function' '*' Identifier '(' FormalParameters ')' '{' FunctionBody '}'
   //
   // 'function' and '*' (if present) have been consumed by the caller.
+  const bool is_generator = flags & ParseFunctionFlags::kIsGenerator;
+  const bool is_async = flags & ParseFunctionFlags::kIsAsync;
+  DCHECK(!is_generator || !is_async);
+
   bool is_strict_reserved = false;
   const AstRawString* name = ParseIdentifierOrStrictReservedWord(
       &is_strict_reserved, CHECK_OK);
 
+  if (V8_UNLIKELY(is_async_function() && this->IsAwait(name))) {
+    ReportMessageAt(scanner()->location(),
+                    MessageTemplate::kAwaitBindingIdentifier);
+    *ok = false;
+    return nullptr;
+  }
+
   FuncNameInferrer::State fni_state(fni_);
   if (fni_ != NULL) fni_->PushEnclosingName(name);
   FunctionLiteral* fun = ParseFunctionLiteral(
       name, scanner()->location(),
       is_strict_reserved ? kFunctionNameIsStrictReserved
                          : kFunctionNameValidityUnknown,
       is_generator ? FunctionKind::kGeneratorFunction
-                   : FunctionKind::kNormalFunction,
+                   : is_async ? FunctionKind::kAsyncFunction
+                              : FunctionKind::kNormalFunction,
       pos, FunctionLiteral::kDeclaration, language_mode(), CHECK_OK);
 
   // Even if we're not at the top-level of the global or a function
   // scope, we treat it as such and introduce the function with its
   // initial value upon entering the corresponding scope.
   // In ES6, a function behaves as a lexical binding, except in
   // a script scope, or the initial scope of eval or another function.
   VariableMode mode =
       (!scope_->is_declaration_scope() || scope_->is_module_scope()) ? LET
                                                                      : VAR;
@@ skipping 292 matching lines @@
         return true;
       }
     }
   }
   return false;
 }
 
 Statement* Parser::ParseFunctionDeclaration(bool* ok) {
   Consume(Token::FUNCTION);
   int pos = position();
-  bool is_generator = Check(Token::MUL);
-  if (allow_harmony_restrictive_declarations() && is_generator) {
-    ParserTraits::ReportMessageAt(
-        scanner()->location(),
-        MessageTemplate::kGeneratorInLegacyContext);
-    *ok = false;
-    return nullptr;
+  ParseFunctionFlags flags = ParseFunctionFlags::kIsNormal;
+  if (Check(Token::MUL)) {
+    flags |= ParseFunctionFlags::kIsGenerator;
+    if (allow_harmony_restrictive_declarations()) {
+      ParserTraits::ReportMessageAt(scanner()->location(),
+                                    MessageTemplate::kGeneratorInLegacyContext);
+      *ok = false;
+      return nullptr;
+    }
   }
-  return ParseHoistableDeclaration(pos, is_generator, nullptr, CHECK_OK);
+
+  return ParseHoistableDeclaration(pos, flags, nullptr, CHECK_OK);
 }
 
 Statement* Parser::ParseExpressionOrLabelledStatement(
     ZoneList<const AstRawString*>* labels,
     AllowLabelledFunctionStatement allow_function, bool* ok) {
   // ExpressionStatement | LabelledStatement ::
   //   Expression ';'
   //   Identifier ':' Statement
   //
   // ExpressionStatement[Yield] :
@@ skipping 1622 matching lines @@
     scope_->set_start_position(start_position);
     ParserFormalParameters formals(scope);
     ParseFormalParameterList(&formals, &formals_classifier, CHECK_OK);
     arity = formals.Arity();
     Expect(Token::RPAREN, CHECK_OK);
     int formals_end_position = scanner()->location().end_pos;
 
     CheckArityRestrictions(arity, kind, formals.has_rest, start_position,
                            formals_end_position, CHECK_OK);
     Expect(Token::LBRACE, CHECK_OK);
-
     // Don't include the rest parameter into the function's formal parameter
     // count (esp. the SharedFunctionInfo::internal_formal_parameter_count,
     // which says whether we need to create an arguments adaptor frame).
     if (formals.has_rest) arity--;
 
     // Determine if the function can be parsed lazily. Lazy parsing is different
     // from lazy compilation; we need to parse more eagerly than we compile.
 
     // We can only parse lazily if we also compile lazily. The heuristics for
     // lazy compilation are:
@@ skipping 135 matching lines @@
       expected_property_count, arity, duplicate_parameters, function_type,
       eager_compile_hint, kind, pos);
   function_literal->set_function_token_position(function_token_pos);
   if (should_be_used_once_hint)
     function_literal->set_should_be_used_once_hint();
 
   if (fni_ != NULL && should_infer_name) fni_->AddFunction(function_literal);
   return function_literal;
 }
 
+Expression* Parser::ParseAsyncFunctionExpression(bool* ok) {
+  // AsyncFunctionDeclaration ::
+  //   async [no LineTerminator here] function ( FormalParameters[Await] )
+  //       { AsyncFunctionBody }
+  //
+  //   async [no LineTerminator here] function BindingIdentifier[Await]
+  //       ( FormalParameters[Await] ) { AsyncFunctionBody }
+  DCHECK_EQ(scanner()->current_token(), Token::ASYNC);
+  int pos = position();
+  Expect(Token::FUNCTION, CHECK_OK);
+  bool is_strict_reserved = false;
+  const AstRawString* name = nullptr;
+  FunctionLiteral::FunctionType type = FunctionLiteral::kAnonymousExpression;
+
+  if (peek_any_identifier()) {
+    type = FunctionLiteral::kNamedExpression;
+    name = ParseIdentifierOrStrictReservedWord(&is_strict_reserved, CHECK_OK);
+    if (this->IsAwait(name)) {
+      ReportMessageAt(scanner()->location(),
+                      MessageTemplate::kAwaitBindingIdentifier);
+      *ok = false;
+      return nullptr;
+    }
+  }
+  return ParseFunctionLiteral(name, scanner()->location(),
+                              is_strict_reserved ? kFunctionNameIsStrictReserved
+                                                 : kFunctionNameValidityUnknown,
+                              FunctionKind::kAsyncFunction, pos, type,
+                              language_mode(), CHECK_OK);
+}
 
 void Parser::SkipLazyFunctionBody(int* materialized_literal_count,
                                   int* expected_property_count, bool* ok,
                                   Scanner::BookmarkScope* bookmark) {
   DCHECK_IMPLIES(bookmark, bookmark->HasBeenSet());
   if (produce_cached_parse_data()) CHECK(log_);
 
   int function_block_pos = position();
   if (consume_cached_parse_data() && !cached_parse_data_->rejected()) {
     // If we have cached data, we use it to skip parsing the function body. The
@@ skipping 379 matching lines @@
                                         NULL, stack_limit_);
     reusable_preparser_->set_allow_lazy(true);
 #define SET_ALLOW(name) reusable_preparser_->set_allow_##name(allow_##name());
     SET_ALLOW(natives);
     SET_ALLOW(harmony_do_expressions);
     SET_ALLOW(harmony_for_in);
     SET_ALLOW(harmony_function_name);
     SET_ALLOW(harmony_function_sent);
     SET_ALLOW(harmony_exponentiation_operator);
     SET_ALLOW(harmony_restrictive_declarations);
+    SET_ALLOW(harmony_async_await);
 #undef SET_ALLOW
   }
   PreParser::PreParseResult result = reusable_preparser_->PreParseLazyFunction(
       language_mode(), function_state_->kind(), scope_->has_simple_parameters(),
       parsing_module_, logger, bookmark, use_counts_);
   if (pre_parse_timer_ != NULL) {
     pre_parse_timer_->Stop();
   }
   return result;
 }
@@ skipping 50 matching lines @@
   FunctionLiteral* constructor = NULL;
   bool has_seen_constructor = false;
 
   Expect(Token::LBRACE, CHECK_OK);
 
   const bool has_extends = extends != nullptr;
   while (peek() != Token::RBRACE) {
     if (Check(Token::SEMICOLON)) continue;
     FuncNameInferrer::State fni_state(fni_);
     const bool in_class = true;
-    const bool is_static = false;
     bool is_computed_name = false;  // Classes do not care about computed
                                     // property names here.
     ExpressionClassifier property_classifier(this);
     const AstRawString* property_name = nullptr;
     ObjectLiteral::Property* property = ParsePropertyDefinition(
-        &checker, in_class, has_extends, is_static, &is_computed_name,
+        &checker, in_class, has_extends, MethodKind::Normal, &is_computed_name,
         &has_seen_constructor, &property_classifier, &property_name, CHECK_OK);
     RewriteNonPattern(&property_classifier, CHECK_OK);
     if (classifier != nullptr) {
       classifier->Accumulate(&property_classifier,
                              ExpressionClassifier::ExpressionProductions);
     }
 
     if (has_seen_constructor && constructor == NULL) {
       constructor = GetPropertyValue(property)->AsFunctionLiteral();
       DCHECK_NOT_NULL(constructor);
@@ skipping 610 matching lines @@
   for (int i = 0; i < tail_call_expressions.length(); ++i) {
     Expression* expression = tail_call_expressions[i];
     // If only FLAG_harmony_explicit_tailcalls is enabled then expression
     // must be a Call expression.
     DCHECK(FLAG_harmony_tailcalls || !FLAG_harmony_explicit_tailcalls ||
            expression->IsCall());
     MarkTailPosition(expression);
   }
 }
 
+Expression* ParserTraits::ExpressionListToExpression(
+    ZoneList<Expression*>* args) {
+  AstNodeFactory* factory = parser_->factory();
+  Expression* expr = args->at(0);
+  for (int i = 1; i < args->length(); ++i) {
+    expr = factory->NewBinaryOperation(Token::COMMA, expr, args->at(i),
+                                       expr->position());
+  }
+  return expr;
+}
+
 void ParserTraits::RewriteDestructuringAssignments() {
   parser_->RewriteDestructuringAssignments();
 }
 
 Expression* ParserTraits::RewriteExponentiation(Expression* left,
                                                 Expression* right, int pos) {
   return parser_->RewriteExponentiation(left, right, pos);
 }
 
 Expression* ParserTraits::RewriteAssignExponentiation(Expression* left,
                                                       Expression* right,
                                                       int pos) {
   return parser_->RewriteAssignExponentiation(left, right, pos);
 }
 
 void ParserTraits::RewriteNonPattern(Type::ExpressionClassifier* classifier,
                                      bool* ok) {
   parser_->RewriteNonPattern(classifier, ok);
 }
 
+Expression* ParserTraits::RewriteAwaitExpression(Expression* value, int pos) {
+  // TODO(caitp): Implement AsyncFunctionAwait()
+  // per tc39.github.io/ecmascript-asyncawait/#abstract-ops-async-function-await
+  return value;
+}
 
 Zone* ParserTraits::zone() const {
   return parser_->function_state_->scope()->zone();
 }
 
 
 ZoneList<Expression*>* ParserTraits::GetNonPatternList() const {
   return parser_->function_state_->non_patterns_to_rewrite();
 }
 
@@ skipping 1472 matching lines @@
                         try_block, target);
     final_loop = target;
   }
 
   return final_loop;
 }
 
 
 }  // namespace internal
 }  // namespace v8