Implement handling of arrow functions in the parser

src/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/v8.h"
 
 #include "src/api.h"
 #include "src/ast.h"
 #include "src/base/platform/platform.h"
 #include "src/bootstrapper.h"
@@ skipping 764 matching lines @@
       pending_error_arg_(NULL),
       pending_error_char_arg_(NULL) {
   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);
+  set_allow_arrow_functions(FLAG_harmony_arrow_functions);
   set_allow_harmony_numeric_literals(FLAG_harmony_numeric_literals);
   for (int feature = 0; feature < v8::Isolate::kUseCounterFeatureCount;
        ++feature) {
     use_counts_[feature] = 0;
   }
 }
 
 
 FunctionLiteral* Parser::ParseProgram() {
   // TODO(bmeurer): We temporarily need to pass allow_nesting = true here,
@@ skipping 2516 matching lines @@
   Smi* literal_type = Smi::cast(value->get(kLiteralTypeSlot));
   return static_cast<LiteralType>(literal_type->value());
 }
 
 
 Handle<FixedArray> CompileTimeValue::GetElements(Handle<FixedArray> value) {
   return Handle<FixedArray>(FixedArray::cast(value->get(kElementsSlot)));
 }
 
 
+Vector<VariableProxy*> ParserTraits::ParameterListFromExpression(

[marja, 2014/07/01 07:23:40]

Comment from the previous round:

Here you have the same logic in 2 functions; would it be possible to have only
one function which both checks if the expression is a parameter list and
constructs the vector?

+    Expression* expression) {
+  // Parsing the parameter list of an arrow function does not have parameters
+  // (as in: () => ...) returns NULL, so expression being NULL is not an error,
+  // but an valid empty parameter list.
+  if (expression == NULL)
+    return Vector<VariableProxy*>::empty();
+
+  Collector<VariableProxy*> collector;
+
+  // IsValidArrowFunctionParamterList() can be used to check for validity,
+  // here we just ASSERT() that the passed expression is a valid param list.
+  while (expression->IsBinaryOperation()) {
+    BinaryOperation* binop = expression->AsBinaryOperation();
+    ASSERT_EQ(binop->op(), Token::COMMA);
+
+    expression = binop->right();
+    ASSERT(expression->IsVariableProxy());
+    ASSERT(!expression->AsVariableProxy()->is_this());
+    ASSERT(!IsEvalOrArguments(expression->AsVariableProxy()->raw_name()));
+    ASSERT(!IsFutureStrictReserved(expression->AsVariableProxy()->raw_name()));
+
+    collector.Add(expression->AsVariableProxy());
+    expression = binop->left();
+  }
+
+  // Add the remaining item.
+  ASSERT(expression->IsVariableProxy());
+  ASSERT(!expression->AsVariableProxy()->is_this());
+  ASSERT(!IsEvalOrArguments(expression->AsVariableProxy()->raw_name()));
+  ASSERT(!IsFutureStrictReserved(expression->AsVariableProxy()->raw_name()));
+
+  collector.Add(expression->AsVariableProxy());
+  return collector.ToVector();
+}
+
+
+bool ParserTraits::IsValidArrowFunctionParameterList(Expression* expression) {
+  // Case for empty parameter lists:
+  //   () => ...
+  if (expression == NULL)
+    return true;
+
+  // Too many parentheses around expression:
+  //   (( ... )) => ...
+  if (expression->parenthesization_level() > 1)
+    return false;
+
+  // Case for a single parameter:
+  //   (foo) => ...
+  //   foo => ...
+  if (expression->IsVariableProxy()) {
+    if (expression->AsVariableProxy()->is_this()) return false;
+    const AstRawString* raw_name = expression->AsVariableProxy()->raw_name();
+    return !(IsEvalOrArguments(raw_name) || IsFutureStrictReserved(raw_name));
+  }
+
+  // Case for more than one parameter:
+  //   (foo, bar [, ...]) => ...
+  if (expression->IsBinaryOperation()) {
+    BinaryOperation* binop = expression->AsBinaryOperation();
+    return binop->op() == Token::COMMA &&
+        !binop->right()->is_parenthesized() &&
+        !binop->left()->is_parenthesized() &&
+        IsValidArrowFunctionParameterList(binop->right()) &&
+        IsValidArrowFunctionParameterList(binop->left());
+  }
+
+  // Any other kind of expression is not a valid parameter list.
+  return false;
+}
+
+
 FunctionLiteral* Parser::ParseFunctionLiteral(
     const AstRawString* function_name,
     Scanner::Location function_name_location,
     bool name_is_strict_reserved,
     bool is_generator,
     int function_token_pos,
     FunctionLiteral::FunctionType function_type,
     FunctionLiteral::ArityRestriction arity_restriction,
     bool* ok) {
   // Function ::
@@ skipping 399 matching lines @@
 
   if (reusable_preparser_ == NULL) {
     intptr_t stack_limit = isolate()->stack_guard()->real_climit();
     reusable_preparser_ = new 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());
+    reusable_preparser_->set_allow_arrow_functions(allow_arrow_functions());
     reusable_preparser_->set_allow_harmony_numeric_literals(
         allow_harmony_numeric_literals());
   }
   PreParser::PreParseResult result =
       reusable_preparser_->PreParseLazyFunction(strict_mode(),
                                                 is_generator(),
                                                 logger);
   return result;
 }
 
@@ skipping 1113 matching lines @@
     info()->SetAstValueFactory(ast_value_factory_);
   }
   ast_value_factory_ = NULL;
 
   InternalizeUseCounts();
 
   return (result != NULL);
 }
 
 } }  // namespace v8::internal