[destructuring] Implement parameter pattern matching.

test/mjsunit/harmony/destructuring.js

 // Copyright 2015 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.
 //
 // Flags: --harmony-destructuring --harmony-computed-property-names
+// Flags: --harmony-arrow-functions
 
 (function TestObjectLiteralPattern() {
   var { x : x, y : y } = { x : 1, y : 2 };
   assertEquals(1, x);
   assertEquals(2, y);
 
   var {z} = { z : 3 };
   assertEquals(3, z);
 
 
@@ skipping 663 matching lines @@
   var o = { __proto__:null, 'a1':1, 'b2':2 };
   var sx = '';
   var sy = '';
   for (var [x,y] in o) {
     sx += x;
     sy += y;
   }
   assertEquals('ab', sx);
   assertEquals('12', sy);
 }());
+
+
+(function TestParameters() {
+  function f({a, b}) { return a - b; }
+  assertEquals(1, f({a : 6, b : 5}));
+
+  function f1(c, {a, b}) { return c + a - b; }
+  assertEquals(8, f1(7, {a : 6, b : 5}));
+
+  function f2({c, d}, {a, b}) { return c - d + a - b; }
+  assertEquals(7, f2({c : 7, d : 1}, {a : 6, b : 5}));
+
+  function f3([{a, b}]) { return a - b; }
+  assertEquals(1, f3([{a : 6, b : 5}]));
+
+  var g = ({a, b}) => { return a - b; };
+  assertEquals(1, g({a : 6, b : 5}));
+
+  var g1 = (c, {a, b}) => { return c + a - b; };
+  assertEquals(8, g1(7, {a : 6, b : 5}));
+
+  var g2 = ({c, d}, {a, b}) => { return c - d + a - b; };
+  assertEquals(7, g2({c : 7, d : 1}, {a : 6, b : 5}));
+
+  var g3 = ([{a, b}]) => { return a - b; };
+  assertEquals(1, g3([{a : 6, b : 5}]));
+}());
+
+
+(function TestDuplicatesInParameters() {
+  assertThrows("'use strict';function f(x,x){}", SyntaxError);
+  assertThrows("'use strict';function f({x,x}){}", SyntaxError);
+  assertThrows("'use strict';function f(x, {x}){}", SyntaxError);
+  assertThrows("'use strict';var f = (x,x) => {};", SyntaxError);
+  assertThrows("'use strict';var f = ({x,x}) => {};", SyntaxError);
+  assertThrows("'use strict';var f = (x, {x}) => {};", SyntaxError);
+
+  function ok(x) { var x; }; ok();
+  assertThrows("function f({x}) { var x; }; f({});", SyntaxError);
+  assertThrows("'use strict'; function f({x}) { let x = 0; }; f({});", SyntaxError);
+}());