[esnext] prototype runtime implementation for async functions

src/parsing/parser-base.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_PARSER_BASE_H
 #define V8_PARSING_PARSER_BASE_H
 
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
 #include "src/hashmap.h"
@@ skipping 18 matching lines @@
   kDisallowLabelledFunctionStatement,
 };
 
 enum class ParseFunctionFlags {
   kIsNormal = 0,
   kIsGenerator = 1,
   kIsAsync = 2,
   kIsDefault = 4
 };
 
+enum class FunctionBody { Normal, SingleExpression };
+
+enum class FunctionParsePhase { Unknown, FormalParameters, FunctionBody };
+
 static inline ParseFunctionFlags operator|(ParseFunctionFlags lhs,
                                            ParseFunctionFlags rhs) {
   typedef unsigned char T;
   return static_cast<ParseFunctionFlags>(static_cast<T>(lhs) |
                                          static_cast<T>(rhs));
 }
 
 static inline ParseFunctionFlags& operator|=(ParseFunctionFlags& lhs,
                                              const ParseFunctionFlags& rhs) {
   lhs = lhs | rhs;
@@ skipping 257 matching lines @@
     }
     void set_super_location(Scanner::Location location) {
       super_location_ = location;
     }
     void set_return_location(Scanner::Location location) {
       return_location_ = location;
     }
 
     bool is_generator() const { return IsGeneratorFunction(kind_); }
     bool is_async_function() const { return IsAsyncFunction(kind_); }
+    bool is_resumable() const { return is_generator() || is_async_function(); }
 
     FunctionKind kind() const { return kind_; }
     FunctionState* outer() const { return outer_function_state_; }
 
+    bool is_async_function_body() const {
+      return is_async_function() &&
+             parse_phase() == FunctionParsePhase::FunctionBody;
+    }
+
+    FunctionParsePhase parse_phase() const { return parse_phase_; }
+
+    void set_parse_phase(FunctionParsePhase parse_phase) {
+      parse_phase_ = parse_phase;
+    }
+
     void set_generator_object_variable(
         typename Traits::Type::GeneratorVariable* variable) {
       DCHECK(variable != NULL);
-      DCHECK(is_generator());
+      DCHECK(is_resumable());
       generator_object_variable_ = variable;
     }
     typename Traits::Type::GeneratorVariable* generator_object_variable()
         const {
       return generator_object_variable_;
     }
 
     typename Traits::Type::Factory* factory() { return factory_; }
 
     const List<DestructuringAssignment>& destructuring_assignments_to_rewrite()
@@ skipping 85 matching lines @@
     typename Traits::Type::Factory* factory_;
 
     // If true, the next (and immediately following) function literal is
     // preceded by a parenthesis.
     bool next_function_is_parenthesized_;
 
     // The value of the parents' next_function_is_parenthesized_, as it applies
     // to this function. Filled in by constructor.
     bool this_function_is_parenthesized_;
 
+    FunctionParsePhase parse_phase_ = FunctionParsePhase::Unknown;
+
     friend class ParserTraits;
     friend class PreParserTraits;
     friend class Checkpoint;
   };
 
   // This scope sets current ReturnExprContext to given value.
   class ReturnExprScope {
    public:
     explicit ReturnExprScope(FunctionState* function_state,
                              ReturnExprContext return_expr_context)
@@ skipping 275 matching lines @@
 
   typename Traits::Type::Factory* factory() {
     return function_state_->factory();
   }
 
   LanguageMode language_mode() { return scope_->language_mode(); }
   bool is_generator() const { return function_state_->is_generator(); }
   bool is_async_function() const {
     return function_state_->is_async_function();
   }
+  bool is_resumable() const { return function_state_->is_resumable(); }
 
   // Report syntax errors.
   void ReportMessage(MessageTemplate::Template message, const char* arg = NULL,
                      ParseErrorType error_type = kSyntaxError) {
     Scanner::Location source_location = scanner()->location();
     Traits::ReportMessageAt(source_location, message, arg, error_type);
   }
 
   void ReportMessageAt(Scanner::Location location,
                        MessageTemplate::Template message,
@@ skipping 1433 matching lines @@
                                   parenthesized_formals, is_async, CHECK_OK);
     // This reads strangely, but is correct: it checks whether any
     // sub-expression of the parameter list failed to be a valid formal
     // parameter initializer. Since YieldExpressions are banned anywhere
     // in an arrow parameter list, this is correct.
     // TODO(adamk): Rename "FormalParameterInitializerError" to refer to
     // "YieldExpression", which is its only use.
     ValidateFormalParameterInitializer(&arrow_formals_classifier, ok);
 
     Scanner::Location loc(lhs_beg_pos, scanner()->location().end_pos);
-    Scope* scope =
-        this->NewScope(scope_, FUNCTION_SCOPE, FunctionKind::kArrowFunction);
+    Scope* scope = this->NewScope(scope_, FUNCTION_SCOPE,
+                                  is_async ? FunctionKind::kAsyncArrowFunction
+                                           : FunctionKind::kArrowFunction);
     // Because the arrow's parameters were parsed in the outer scope, any
     // usage flags that might have been triggered there need to be copied
     // to the arrow scope.
     scope_->PropagateUsageFlagsToScope(scope);
     FormalParametersT parameters(scope);
     if (!arrow_formals_classifier.is_simple_parameter_list()) {
       scope->SetHasNonSimpleParameters();
       parameters.is_simple = false;
     }
 
@@ skipping 414 matching lines @@
 
         return this->ExpressionFromIdentifier(
             name, beg_pos, scanner()->location().end_pos, scope_, factory());
       }
       default:
         break;
     }
     Consume(Token::AWAIT);
 
     ExpressionT value = ParseUnaryExpression(classifier, CHECK_OK);
-    classifier->RecordFormalParameterInitializerError(
-        Scanner::Location(beg_pos, scanner()->location().end_pos),
-        MessageTemplate::kAwaitExpressionFormalParameter);
-
+    if (!function_state_->is_async_function_body()) {
+      // Not currently parsing function body --- must have occurred within
+      // formal parameter parsing.
+      ReportMessageAt(Scanner::Location(beg_pos, scanner()->location().end_pos),
+                      MessageTemplate::kAwaitExpressionFormalParameter);
+      *ok = false;
+      return this->EmptyExpression();
+    }
     return Traits::RewriteAwaitExpression(value, beg_pos);
   } else {
     return this->ParsePostfixExpression(classifier, ok);
   }
 }
 
 
 template <class Traits>
 typename ParserBase<Traits>::ExpressionT
 ParserBase<Traits>::ParsePostfixExpression(ExpressionClassifier* classifier,
@@ skipping 577 matching lines @@
     *ok = false;
     return this->EmptyExpression();
   }
 
   typename Traits::Type::StatementList body;
   int num_parameters = formal_parameters.scope->num_parameters();
   int materialized_literal_count = -1;
   int expected_property_count = -1;
   Scanner::Location super_loc;
 
+  FunctionKind arrow_kind = is_async ? kAsyncArrowFunction : kArrowFunction;
   {
     typename Traits::Type::Factory function_factory(ast_value_factory());
-    FunctionState function_state(
-        &function_state_, &scope_, formal_parameters.scope,
-        is_async ? kAsyncArrowFunction : kArrowFunction, &function_factory);
+    FunctionState function_state(&function_state_, &scope_,
+                                 formal_parameters.scope, arrow_kind,
+                                 &function_factory);
 
     function_state.SkipMaterializedLiterals(
         formal_parameters.materialized_literals_count);
 
     this->ReindexLiterals(formal_parameters);
 
     Expect(Token::ARROW, CHECK_OK);
+    function_state.set_parse_phase(FunctionParsePhase::FunctionBody);
 
     if (peek() == Token::LBRACE) {
       // Multiple statement body
       Consume(Token::LBRACE);
       bool is_lazily_parsed =
           (mode() == PARSE_LAZILY && scope_->AllowsLazyParsing());
       if (is_lazily_parsed) {
         body = this->NewStatementList(0, zone());
         this->SkipLazyFunctionBody(&materialized_literal_count,
                                    &expected_property_count, CHECK_OK);
         if (formal_parameters.materialized_literals_count > 0) {
           materialized_literal_count +=
               formal_parameters.materialized_literals_count;
         }
       } else {
         body = this->ParseEagerFunctionBody(
             this->EmptyIdentifier(), RelocInfo::kNoPosition, formal_parameters,
-            kArrowFunction, FunctionLiteral::kAnonymousExpression, CHECK_OK);
+            arrow_kind, FunctionLiteral::kAnonymousExpression, CHECK_OK);
         materialized_literal_count =
             function_state.materialized_literal_count();
         expected_property_count = function_state.expected_property_count();
       }
     } else {
       // Single-expression body
       int pos = position();
       ExpressionClassifier classifier(this);
       DCHECK(ReturnExprContext::kInsideValidBlock ==
              function_state_->return_expr_context());
       ReturnExprScope allow_tail_calls(
           function_state_, ReturnExprContext::kInsideValidReturnStatement);
-      ExpressionT expression =
-          ParseAssignmentExpression(accept_IN, &classifier, CHECK_OK);
-      Traits::RewriteNonPattern(&classifier, CHECK_OK);
       body = this->NewStatementList(1, zone());
-      this->AddParameterInitializationBlock(formal_parameters, body, CHECK_OK);
-      body->Add(factory()->NewReturnStatement(expression, pos), zone());
+      this->AddParameterInitializationBlock(formal_parameters, body, is_async,
+                                            CHECK_OK);
+      if (is_async) {
+        this->ParseAsyncArrowSingleExpressionBody(body, accept_IN, &classifier,
+                                                  pos, CHECK_OK);
+        Traits::RewriteNonPattern(&classifier, CHECK_OK);
+      } else {
+        ExpressionT expression =
+            ParseAssignmentExpression(accept_IN, &classifier, CHECK_OK);
+        Traits::RewriteNonPattern(&classifier, CHECK_OK);
+        body->Add(factory()->NewReturnStatement(expression, pos), zone());
+        if (allow_tailcalls() && !is_sloppy(language_mode())) {
+          // ES6 14.6.1 Static Semantics: IsInTailPosition
+          this->MarkTailPosition(expression);
+        }
+      }
       materialized_literal_count = function_state.materialized_literal_count();
       expected_property_count = function_state.expected_property_count();
-      if (allow_tailcalls() && !is_sloppy(language_mode())) {
-        // ES6 14.6.1 Static Semantics: IsInTailPosition
-        this->MarkTailPosition(expression);
-      }
       this->MarkCollectedTailCallExpressions();
     }
     super_loc = function_state.super_location();
 
     formal_parameters.scope->set_end_position(scanner()->location().end_pos);
 
     // Arrow function formal parameters are parsed as StrictFormalParameterList,
     // which is not the same as "parameters of a strict function"; it only means
     // that duplicates are not allowed.  Of course, the arrow function may
     // itself be strict as well.
     const bool allow_duplicate_parameters = false;
     this->ValidateFormalParameters(&formals_classifier, language_mode(),
                                    allow_duplicate_parameters, CHECK_OK);
 
     // Validate strict mode.
     if (is_strict(language_mode())) {
       CheckStrictOctalLiteral(formal_parameters.scope->start_position(),
                               scanner()->location().end_pos, CHECK_OK);
     }
     this->CheckConflictingVarDeclarations(formal_parameters.scope, CHECK_OK);
 
     Traits::RewriteDestructuringAssignments();
   }
 
   FunctionLiteralT function_literal = factory()->NewFunctionLiteral(
       this->EmptyIdentifierString(), formal_parameters.scope, body,
       materialized_literal_count, expected_property_count, num_parameters,
       FunctionLiteral::kNoDuplicateParameters,
       FunctionLiteral::kAnonymousExpression,
-      FunctionLiteral::kShouldLazyCompile, FunctionKind::kArrowFunction,
+      FunctionLiteral::kShouldLazyCompile, arrow_kind,
       formal_parameters.scope->start_position());
 
   function_literal->set_function_token_position(
       formal_parameters.scope->start_position());
   if (super_loc.IsValid()) function_state_->set_super_location(super_loc);
 
   if (fni_ != NULL) this->InferFunctionName(fni_, function_literal);
 
   return function_literal;
 }
@@ skipping 209 matching lines @@
     has_seen_constructor_ = true;
     return;
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H