[es6] Implement destructuring for `catch`

src/preparser.cc

Index: src/preparser.cc
diff --git a/src/preparser.cc b/src/preparser.cc
index b1541f616afe133554881e99aec4f71a9f5e45e0..a104678f9fb0f43a9ea6a75d9bf8c0d127536973 100644
--- a/src/preparser.cc
+++ b/src/preparser.cc
@@ -496,15 +496,11 @@ PreParser::Statement PreParser::ParseVariableDeclarations(
   // VariableDeclarations ::
   //   ('var' | 'const') (Identifier ('=' AssignmentExpression)?)+[',']
   //
-  // The ES6 Draft Rev3 specifies the following grammar for const declarations
-  //
   // ConstDeclaration ::
   //   const ConstBinding (',' ConstBinding)* ';'
-  // ConstBinding ::
-  //   Identifier '=' AssignmentExpression
   //
-  // TODO(ES6):
   // ConstBinding ::
+  //   Identifier '=' AssignmentExpression
   //   BindingPattern '=' AssignmentExpression
   bool require_initializer = false;
   bool is_strict_const = false;
@@ -980,6 +976,7 @@ PreParser::Statement PreParser::ParseTryStatement(bool* ok) {
   //
   // Catch ::
   //   'catch' '(' Identifier ')' Block
+  //   'catch' '(' BindingPattern ')' Block
   //
   // Finally ::
   //   'finally' Block
@@ -997,11 +994,29 @@ PreParser::Statement PreParser::ParseTryStatement(bool* ok) {
   if (tok == Token::CATCH) {
     Consume(Token::CATCH);
     Expect(Token::LPAREN, CHECK_OK);
-    ParseIdentifier(kDontAllowRestrictedIdentifiers, CHECK_OK);
+
+    ExpressionClassifier pattern_classifier;
+    Token::Value next = peek();
+    PreParserExpression pattern =
+        ParsePrimaryExpression(&pattern_classifier, CHECK_OK);
+    ValidateBindingPattern(&pattern_classifier, CHECK_OK);
+
+    if (!allow_harmony_destructuring() && !pattern.IsIdentifier()) {
+      ReportUnexpectedToken(next);
+      *ok = false;
+      return Statement::Default();
+    }
+
     Expect(Token::RPAREN, CHECK_OK);
-    {
-      Scope* with_scope = NewScope(scope_, WITH_SCOPE);
-      BlockState block_state(&scope_, with_scope);
+
+    if (pattern.IsIdentifier()) {
+      Scope* catch_scope = NewScope(scope_, CATCH_SCOPE);
+      BlockState block_state(&scope_, catch_scope);
+      ParseBlock(CHECK_OK);
+    } else {
+      Scope* catch_scope = NewScope(scope_, CATCH_SCOPE);
+      Scope* destruct_scope = NewScope(catch_scope, BLOCK_SCOPE);
+      BlockState block_state(&scope_, destruct_scope);
       ParseBlock(CHECK_OK);
     }
     tok = peek();