[esnext] implement frontend changes for async/await proposal

src/parsing/preparser.cc

 // Copyright 2011 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 <cmath>
 
 #include "src/allocation.h"
 #include "src/base/logging.h"
 #include "src/conversions-inl.h"
 #include "src/conversions.h"
@@ skipping 33 matching lines @@
     return PreParserIdentifier::Await();
   } else if (scanner->current_token() ==
              Token::FUTURE_STRICT_RESERVED_WORD) {
     return PreParserIdentifier::FutureStrictReserved();
   } else if (scanner->current_token() == Token::LET) {
     return PreParserIdentifier::Let();
   } else if (scanner->current_token() == Token::STATIC) {
     return PreParserIdentifier::Static();
   } else if (scanner->current_token() == Token::YIELD) {
     return PreParserIdentifier::Yield();
+  } else if (scanner->current_token() == Token::ASYNC) {
+    return PreParserIdentifier::Async();
   }
   if (scanner->UnescapedLiteralMatches("eval", 4)) {
     return PreParserIdentifier::Eval();
   }
   if (scanner->UnescapedLiteralMatches("arguments", 9)) {
     return PreParserIdentifier::Arguments();
   }
   if (scanner->UnescapedLiteralMatches("undefined", 9)) {
     return PreParserIdentifier::Undefined();
   }
@@ skipping 122 matching lines @@
       return ParseHoistableDeclaration(ok);
     case Token::CLASS:
       return ParseClassDeclaration(ok);
     case Token::CONST:
       return ParseVariableStatement(kStatementListItem, ok);
     case Token::LET:
       if (IsNextLetKeyword()) {
         return ParseVariableStatement(kStatementListItem, ok);
       }
       break;
+    case Token::ASYNC:
+      if (allow_harmony_async_await() && PeekAhead() == Token::FUNCTION &&
+          !scanner()->HasAnyLineTerminatorAfterNext()) {
+        Consume(Token::ASYNC);
+        return ParseAsyncFunctionDeclaration(ok);
+      }
+    /* falls through */
     default:
       break;
   }
   return ParseStatement(kAllowLabelledFunctionStatement, ok);
 }
 
 
 void PreParser::ParseStatementList(int end_token, bool* ok,
                                    Scanner::BookmarkScope* bookmark) {
   // SourceElements ::
@@ skipping 168 matching lines @@
       return ParseDebuggerStatement(ok);
 
     case Token::VAR:
       return ParseVariableStatement(kStatement, ok);
 
     default:
       return ParseExpressionOrLabelledStatement(allow_function, ok);
   }
 }
 
+PreParser::Statement PreParser::ParseHoistableDeclaration(
+    int pos, ParseFunctionFlags flags, bool* ok) {
+  const bool is_generator = flags & ParseFunctionFlags::kIsGenerator;
+  const bool is_async = flags & ParseFunctionFlags::kIsAsync;
+  DCHECK(!is_generator || !is_async);
 
-PreParser::Statement PreParser::ParseHoistableDeclaration(
-    int pos, bool is_generator, bool* ok) {
   bool is_strict_reserved = false;
   Identifier name = ParseIdentifierOrStrictReservedWord(
       &is_strict_reserved, CHECK_OK);
+
+  if (V8_UNLIKELY(is_async_function() && this->IsAwait(name))) {
+    ReportMessageAt(scanner()->location(),
+                    MessageTemplate::kAwaitBindingIdentifier);
+    *ok = false;
+    return Statement::Default();
+  }
+
   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);
   return Statement::FunctionDeclaration();
 }
 
+PreParser::Statement PreParser::ParseAsyncFunctionDeclaration(bool* ok) {
+  // AsyncFunctionDeclaration ::
+  //   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);
+  ParseFunctionFlags flags = ParseFunctionFlags::kIsAsync;
+  return ParseHoistableDeclaration(pos, flags, ok);
+}
 
 PreParser::Statement PreParser::ParseHoistableDeclaration(bool* ok) {
   // FunctionDeclaration ::
   //   'function' Identifier '(' FormalParameterListopt ')' '{' FunctionBody '}'
   // GeneratorDeclaration ::
   //   'function' '*' Identifier '(' FormalParameterListopt ')'
   //      '{' FunctionBody '}'
+
   Expect(Token::FUNCTION, CHECK_OK);
   int pos = position();
-  bool is_generator = Check(Token::MUL);
-  return ParseHoistableDeclaration(pos, is_generator, CHECK_OK);
+  ParseFunctionFlags flags = ParseFunctionFlags::kIsNormal;
+  if (Check(Token::MUL)) {
+    flags |= ParseFunctionFlags::kIsGenerator;
+  }
+  return ParseHoistableDeclaration(pos, flags, ok);
 }
 
 
 PreParser::Statement PreParser::ParseClassDeclaration(bool* ok) {
   Expect(Token::CLASS, CHECK_OK);
 
   int pos = position();
   bool is_strict_reserved = false;
   Identifier name =
       ParseIdentifierOrStrictReservedWord(&is_strict_reserved, CHECK_OK);
@@ skipping 138 matching lines @@
 
   if (num_decl != nullptr) *num_decl = nvars;
   if (is_lexical != nullptr) *is_lexical = lexical;
   if (is_binding_pattern != nullptr) *is_binding_pattern = is_pattern;
   return Statement::Default();
 }
 
 PreParser::Statement PreParser::ParseFunctionDeclaration(bool* ok) {
   Consume(Token::FUNCTION);
   int pos = position();
-  bool is_generator = Check(Token::MUL);
-  if (allow_harmony_restrictive_declarations() && is_generator) {
-    PreParserTraits::ReportMessageAt(
-        scanner()->location(),
-        MessageTemplate::kGeneratorInLegacyContext);
-    *ok = false;
-    return Statement::Default();
+  ParseFunctionFlags flags = ParseFunctionFlags::kIsNormal;
+  if (Check(Token::MUL)) {
+    flags |= ParseFunctionFlags::kIsGenerator;
+    if (allow_harmony_restrictive_declarations()) {
+      PreParserTraits::ReportMessageAt(
+          scanner()->location(), MessageTemplate::kGeneratorInLegacyContext);
+      *ok = false;
+      return Statement::Default();
+    }
   }
-  return ParseHoistableDeclaration(pos, is_generator, ok);
+  return ParseHoistableDeclaration(pos, flags, ok);
 }
 
 PreParser::Statement PreParser::ParseExpressionOrLabelledStatement(
     AllowLabelledFunctionStatement allow_function, bool* ok) {
   // ExpressionStatement | LabelledStatement ::
   //   Expression ';'
   //   Identifier ':' Statement
 
   switch (peek()) {
     case Token::FUNCTION:
@@ skipping 516 matching lines @@
                            allow_duplicate_parameters, CHECK_OK);
 
   if (is_strict(language_mode)) {
     int end_position = scanner()->location().end_pos;
     CheckStrictOctalLiteral(start_position, end_position, CHECK_OK);
   }
 
   return Expression::Default();
 }
 
+PreParser::Expression PreParser::ParseAsyncFunctionExpression(bool* ok) {
+  // AsyncFunctionDeclaration ::
+  //   async [no LineTerminator here] function ( FormalParameters[Await] )
+  //       { AsyncFunctionBody }
+  //
+  //   async [no LineTerminator here] function BindingIdentifier[Await]
+  //       ( FormalParameters[Await] ) { AsyncFunctionBody }
+  int pos = position();
+  Expect(Token::FUNCTION, CHECK_OK);
+  bool is_strict_reserved = false;
+  Identifier name;
+  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 Expression::Default();
+    }
+  }
+
+  ParseFunctionLiteral(name, scanner()->location(),
+                       is_strict_reserved ? kFunctionNameIsStrictReserved
+                                          : kFunctionNameValidityUnknown,
+                       FunctionKind::kAsyncFunction, pos, type, language_mode(),
+                       CHECK_OK);
+  return Expression::Default();
+}
 
 void PreParser::ParseLazyFunctionLiteralBody(bool* ok,
                                              Scanner::BookmarkScope* bookmark) {
   int body_start = position();
   ParseStatementList(Token::RBRACE, ok, bookmark);
   if (!*ok) return;
   if (bookmark && bookmark->HasBeenReset()) return;
 
   // Position right after terminal '}'.
   DCHECK_EQ(Token::RBRACE, scanner()->peek());
@@ skipping 41 matching lines @@
     }
   }
 
   ClassLiteralChecker checker(this);
   bool has_seen_constructor = false;
 
   Expect(Token::LBRACE, CHECK_OK);
   while (peek() != Token::RBRACE) {
     if (Check(Token::SEMICOLON)) continue;
     const bool in_class = true;
-    const bool is_static = false;
     bool is_computed_name = false;  // Classes do not care about computed
                                     // property names here.
     Identifier name;
     ExpressionClassifier property_classifier(this);
-    ParsePropertyDefinition(&checker, in_class, has_extends, is_static,
+    ParsePropertyDefinition(&checker, in_class, has_extends, MethodKind::Normal,
                             &is_computed_name, &has_seen_constructor,
                             &property_classifier, &name, CHECK_OK);
     ValidateExpression(&property_classifier, CHECK_OK);
     if (classifier != nullptr) {
       classifier->Accumulate(&property_classifier,
                              ExpressionClassifier::ExpressionProductions);
     }
   }
 
   Expect(Token::RBRACE, CHECK_OK);
@@ skipping 33 matching lines @@
   }
   Expect(Token::RBRACE, CHECK_OK);
   return PreParserExpression::Default();
 }
 
 #undef CHECK_OK
 
 
 }  // namespace internal
 }  // namespace v8