[parser] Fix bug in destructuring binding for catch.

For variables introduced as part of a catch pattern, we used to set their
"initializer position" to the beginning of the pattern.  This lead to
full-codegen eliminating crucial hole checks when reading such variables
inside the pattern itself.

R=adamk@chromium.org, littledan@chromium.org
BUG=v8:5178

Review-Url: https://codereview.chromium.org/2123953002
Cr-Commit-Position: refs/heads/master@{#37569}

src/parsing/parser.cc

@@ -3017,8 +3017,11 @@ TryStatement* Parser::ParseTryStatement(bool* ok) {
           descriptor.declaration_pos = pattern->position();
           descriptor.initialization_pos = pattern->position();
 
+          // Initializer position for variables declared by the pattern.
+          const int initializer_position = position();
+
           DeclarationParsingResult::Declaration decl(
-              pattern, pattern->position(),
+              pattern, initializer_position,
               factory()->NewVariableProxy(catch_variable));
 
           Block* init_block =

src/parsing/parser.h

@@ -854,8 +854,6 @@ class Parser : public ParserBase<ParserTraits> {
                                                       Assignment* assignment,
                                                       Scope* scope);
 
-    void set_initializer_position(int pos) { initializer_position_ = pos; }
-
    private:
     PatternRewriter() {}
 

test/mjsunit/regress/regress-5178.js

+// Copyright 2016 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.
+
+assertThrows(() => {
+  try { throw {} } catch({a=b, b}) { a+b }
+}, ReferenceError);