Implement handling of arrow functions in the parser

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index d882c1e69d9ecff0c360bf38febc05bef241ce2c..99f952232b04094c653e0023bbf8247ee5652a7c 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -782,6 +782,7 @@ Parser::Parser(CompilationInfo* info)
   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) {
@@ -3318,6 +3319,79 @@ Handle<FixedArray> CompileTimeValue::GetElements(Handle<FixedArray> value) {
 }
 
 
+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,
@@ -3737,6 +3811,7 @@ PreParser::PreParseResult Parser::ParseLazyFunctionBodyWithPreParser(
     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());
   }