deopt array unpack optimisation on member expressions - fixes #1241

src/babel/transformation/transformers/es6/destructuring.js

@@ -403,9 +403,14 @@ class DestructuringTransformer {
     if (pattern.elements.length > arr.elements.length) return;
     if (pattern.elements.length < arr.elements.length && !hasRest(pattern)) return false;
 
-    // deopt on holes
     for (var i = 0; i < pattern.elements.length; i++) {
-      if (!pattern.elements[i]) return false;
+      var elem = pattern.elements[i];
+
+      // deopt on holes
+      if (!elem) return false;
+
+      // deopt on member expressions
+      if (t.isMemberExpression(elem)) return false;
     }
 
     // deopt on reference to left side identifiers

test/core/fixtures/transformation/es6.destructuring/array-unpack-optimisation/actual.js

@@ -8,3 +8,4 @@ var [[a, b, ...c]] = [[1, 2, 3, 4]];
 var [a, b] = [1, 2, 3];
 var [[a, b]] = [[1, 2, 3]];
 var [a, b] = [a, b];
+[a[0], a[1]] = [a[1], a[0]];

test/core/fixtures/transformation/es6.destructuring/array-unpack-optimisation/expected.js

@@ -22,3 +22,7 @@ var b = _ref2[1];
 var _ref3 = [a, b];
 var a = _ref3[0];
 var b = _ref3[1];
+var _temp = [a[1], a[0]];
+a[0] = _temp[0];
+a[1] = _temp[1];
+_temp;

test/core/fixtures/transformation/es6.destructuring/member-expression/expected.js

@@ -1,6 +1,7 @@
 "use strict";
 
-foo.foo = 1;
-foo.bar = 2;
+var _ref = [1, 2];
+foo.foo = _ref[0];
+foo.bar = _ref[1];
 
 ;