[destructuring] Parse binding patterns in formal parameters.

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index 96c269546f755b6a706a4cc9d13b555453ad3d25..53cc0f5a1f7fbc6f823fe8c7c7ced5f3f1e1cee8 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -1183,13 +1183,16 @@ FunctionLiteral* Parser::ParseLazy(Isolate* isolate, ParseInfo* info,
       scope->set_start_position(shared_info->start_position());
       ExpressionClassifier formals_classifier;
       bool has_rest = false;
-      if (Check(Token::LPAREN)) {
-        // '(' StrictFormalParameters ')'
-        ParseFormalParameterList(scope, &has_rest, &formals_classifier, &ok);
-        if (ok) ok = Check(Token::RPAREN);
-      } else {
-        // BindingIdentifier
-        ParseFormalParameter(scope, has_rest, &formals_classifier, &ok);
+      {
+        BlockState block_state(&scope_, scope);

[arv (Not doing code reviews), 2015/06/15 15:21:59]

Why was this block state added? It does not seem like it is needed for parsing.

[Dmitry Lomov (no reviews), 2015/06/15 16:12:51]

Ah, this is a tricky bit. Parsing patterns as variable reference expressions
creates NewUnresolved references in current scope. This BlockState makes arrow
function scope the current scope - otherwise we will create NewUnresolved in
outer scope - this is logically wrong, but not only - in case of lazy parsing
the outer scope is immutable, so we assert.

+        if (Check(Token::LPAREN)) {
+          // '(' StrictFormalParameters ')'
+          ParseFormalParameterList(scope, &has_rest, &formals_classifier, &ok);
+          if (ok) ok = Check(Token::RPAREN);
+        } else {
+          // BindingIdentifier
+          ParseFormalParameter(scope, has_rest, &formals_classifier, &ok);
+        }
       }
 
       if (ok) {
@@ -3803,7 +3806,11 @@ void ParserTraits::ParseArrowFunctionFormalParameters(
     expr = expr->AsSpread()->expression();
   }
 
-  DCHECK(expr->IsVariableProxy());
+  if (!expr->IsVariableProxy()) {
+    // TODO(dslomov): support pattern desugaring
+    return;
+  }
+  // TODO(wingo): Support rest parameters.

[arv (Not doing code reviews), 2015/06/15 15:21:59]

Andy implemented this last week.

[Dmitry Lomov (no reviews), 2015/06/15 16:12:51]

Removed.

   DCHECK(!expr->AsVariableProxy()->is_this());
 
   const AstRawString* raw_name = expr->AsVariableProxy()->raw_name();
@@ -3816,7 +3823,7 @@ void ParserTraits::ParseArrowFunctionFormalParameters(
   parser_->scope_->RemoveUnresolved(expr->AsVariableProxy());
 
   ExpressionClassifier classifier;
-  DeclareFormalParameter(scope, raw_name, &classifier, *has_rest);
+  DeclareFormalParameter(scope, expr, &classifier, *has_rest);
   if (!duplicate_loc->IsValid()) {
     *duplicate_loc = classifier.duplicate_formal_parameter_error().location;
   }