track arrays to avoid turning something into an array multiple times - closes #757

test/fixtures/transformation/es6-destructuring/known-array/actual.js

@@ -0,0 +1 @@
+let [x, ...y] = z;

test/fixtures/transformation/es6-destructuring/known-array/expected.js

@@ -0,0 +1,8 @@
+"use strict";
+
+var _toArray = function (arr) { return Array.isArray(arr) ? arr : Array.from(arr); };
+
+var _z = _toArray(z);
+
+var x = _z[0];
+var y = _z.slice(1);

test/fixtures/transformation/es6-destructuring/spread/expected.js

@@ -7,9 +7,9 @@ var isSorted = function (_ref) {
 
   var x = _ref2[0];
   var y = _ref2[1];
-  var wow = _toArray(_ref2).slice(2);
+  var wow = _ref2.slice(2);
 
   if (!zs.length) return true;
   if (y > x) return isSorted(zs);
   return false;
-};
+};

test/fixtures/transformation/es6-parameters.rest/pattern/expected.js

@@ -1,14 +1,11 @@
 "use strict";
 
-var _slicedToArray = function (arr, i) { if (Array.isArray(arr)) { return arr; } else { var _arr = []; for (var _iterator = arr[Symbol.iterator](), _step; !(_step = _iterator.next()).done;) { _arr.push(_step.value); if (i && _arr.length === i) break; } return _arr; } };
-
 var foo = function () {
   for (var _len = arguments.length, _ref = Array(_len), _key = 0; _key < _len; _key++) {
     _ref[_key] = arguments[_key];
   }
 
-  var _ref2 = _slicedToArray(_ref, 2);
-
+  var _ref2 = _ref;
   var a = _ref2[0];
   var b = _ref2[1];
 };

test/fixtures/transformation/es6-spread/known-array/actual.js

@@ -0,0 +1,2 @@
+var arr: Array = bar;
+[...arr];

test/fixtures/transformation/es6-spread/known-array/expected.js

@@ -0,0 +1,4 @@
+"use strict";
+
+var arr = bar;
+[].concat(arr);

test/fixtures/transformation/es6-spread/known-rest/actual.js

@@ -0,0 +1,3 @@
+function foo(...bar) {
+  return [...bar];
+}

test/fixtures/transformation/es6-spread/known-rest/expected.js

@@ -0,0 +1,9 @@
+"use strict";
+
+function foo() {
+  for (var _len = arguments.length, bar = Array(_len), _key = 0; _key < _len; _key++) {
+    bar[_key] = arguments[_key];
+  }
+
+  return [].concat(bar);
+}