Set the correct scope when initializing parameters.

If the parameter list contains class declarations we should use the
block scope corresponding to the class when rewriting the initializers.

Bug: chromium:917988
Change-Id: I7fcd44a264b7c0113cbd821b759e0bee6c9345a0
Reviewed-on: https://chromium-review.googlesource.com/c/1392240
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58515}

src/parsing/parser.cc

@@ -2842,8 +2842,18 @@ Block* Parser::BuildParameterInitializationBlock(
     if (parameter->initializer() != nullptr) {
       // IS_UNDEFINED($param) ? initializer : $param
 
-      // Ensure initializer is rewritten
+      if (parameter->initializer()->IsClassLiteral()) {
-      RewriteParameterInitializer(parameter->initializer());
+        //  Initializers could have their own scopes. So set the scope
+        //  here if necessary.
+        BlockState block_state(
+            &scope_, parameter->initializer()->AsClassLiteral()->scope());
+
+        // Ensure initializer is rewritten
+        RewriteParameterInitializer(parameter->initializer());
+      } else {
+        // Ensure initializer is rewritten
+        RewriteParameterInitializer(parameter->initializer());
+      }
 
       auto condition = factory()->NewCompareOperation(
           Token::EQ_STRICT,

test/mjsunit/regress/regress-917988.js

@@ -0,0 +1,31 @@
+// Copyright 2018 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.
+
+// Tests if class declarations in parameter list are correctly handled.
+function v_2(
+v_3 = class v_4 {
+    get [[] = ';']() { }
+}
+) { }
+v_2();
+
+// Test object inside a class in a parameter list
+(function f(
+v_3 = class v_4 {
+    get [{} = ';']() { }
+}
+) { })();
+
+// Test destructuring of class in parameters
+(function f( {p, q} = class C { get [[] = ';']() {} } ) {})();
+
+// Test array destructuring of class in parameters
+class C {};
+C[Symbol.iterator] = function() {
+  return {
+    next: function() { return { done: true }; },
+    _first: true
+  };
+};
+(function f1([p, q] = class D extends C { get [[]]() {} }) { })();