1 files changed, 124 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/basic/destructuring-iterator.js b/js/src/jit-test/tests/basic/destructuring-iterator.js
new file mode 100644
index 0000000000..ca65930242
--- /dev/null
+++ b/js/src/jit-test/tests/basic/destructuring-iterator.js
@@ -0,0 +1,124 @@
+
+load(libdir + 'asserts.js');
+load(libdir + 'iteration.js');
+load(libdir + 'eqArrayHelper.js');
+
+// throw on non-iterables
+assertThrowsInstanceOf(() => { [a, b, c] = {0: 0, 1: 1, 2: 2} }, TypeError);
+
+var nextcalls = 0, donecalls = 0, valuecalls = 0;
+var doneafter = 0;
+var iterable = {};
+iterable[Symbol.iterator] = function () {
+  return {
+    next: function () {
+      assertEq(arguments.length, 0, 'iterator.next() should be called with no arguments');
+      nextcalls++;
+      return {
+        get done() {
+          donecalls++;
+          return --doneafter < 0;
+        },
+        get value() {
+          valuecalls++;
+          return valuecalls;
+        }
+      };
+    }
+  }
+};
+
+function assertIterable(expectCalls, fn, expectResult) {
+  [nextcalls, donecalls, valuecalls, doneafter] = [0,0,0, expectCalls[3]];
+  assertEqArray(fn(iterable), expectResult);
+  assertEq(nextcalls,  expectCalls[0], 'calls to iterator.next()');
+  assertEq(donecalls,  expectCalls[1], 'getting iterator.next().done');
+  assertEq(valuecalls, expectCalls[2], 'getting iterator.next().value');
+}
+
+assertIterable([1,1,1,1],
+  it => { var [a] = it; return [a]; },
+  [1]);
+assertIterable([2,2,1,1],
+  it => { var [a,b,c] = it; return [a,b,c]; },
+  [1,undefined,undefined]);
+assertIterable([2,2,1,1],
+  it => { var [a,b,...rest] = it; return [a,b,...rest]; },
+  [1,undefined]);
+assertIterable([5,5,4,4],
+  it => { var [,,...rest] = it; return rest; },
+  [3,4]);
+
+// the iterator should be exhausted before any error is thrown
+assertIterable([5,5,4,4],
+  it => {
+    assertThrowsInstanceOf(function () {
+      "use strict";
+      [...{0: "".x}] = it;
+    }, TypeError);
+    return [];
+  },
+  []);
+
+var arraycalls = 0;
+var ArrayIterator = Array.prototype[Symbol.iterator];
+Array.prototype[Symbol.iterator] = function () {
+  arraycalls++;
+  return ArrayIterator.apply(this, arguments);
+};
+// [...rest] should not call Array#@@iterator for the LHS
+var [...rest] = iterable;
+assertEq(arraycalls, 0, 'calls to Array#@@iterator');
+// [...[...rest]] should do so, since it creates an implicit array for the
+// first rest pattern, then destructures that again using @@iterator() for the
+// second rest pattern.
+var [...[...rest]] = iterable;
+assertEq(arraycalls, 1, 'calls to Array#@@iterator');
+
+// loop `fn` a few times, to get it JIT-compiled
+function loop(fn) {
+  var i = 1e4;
+  while (i--) fn();
+}
+
+loop(() => { doneafter = 4; var [a] = iterable; return a; });
+loop(() => { doneafter = 4; var [a,b,...[...rest]] = iterable; return rest; });
+
+
+// destructuring assignment should always use iterators and not optimize
+// to a "group assignment"
+delete Array.prototype[Symbol.iterator];
+assertThrowsInstanceOf(() => { var [a,b] = [1,2]; }, TypeError);
+Array.prototype[Symbol.iterator] = ArrayIterator;
+
+// observe the binding order
+a = undefined, b = undefined, c = undefined;
+var obj = {};
+obj[Symbol.iterator] = function* () {
+	// normal fields should be initialized right after |.next()|
+	yield 1;
+	assertEq(a, 1);
+	yield 2;
+	yield 3;
+	assertEq(b, 3);
+	yield 4;
+	yield 5;
+	// rest should be initialized after the iterator is exhausted
+	assertEq(c, undefined);
+};
+[a, , b, ...c] = obj;
+assertEqArray(c, [4,5]);
+
+// a throw inside the destructuring of the "catch" value should not enter
+// the "catch" block
+
+assertThrowsValue(function () {
+  try {
+    Array.prototype[Symbol.iterator] = function () { throw 'from iterator'; };
+    throw [1, 2];
+  } catch ([x, y]) {
+    throw 'not reached';
+  }
+}, 'from iterator');
+Array.prototype[Symbol.iterator] = ArrayIterator;
+