Merge pull request #5093 from existentialism/issue5090

Ensure array is always copied during destructure

packages/babel-plugin-transform-es2015-destructuring/src/index.js

@@ -294,10 +294,7 @@ export default function ({ types: t }) {
 
         if (t.isRestElement(elem)) {
           elemRef = this.toArray(arrayRef);
-
-          if (i > 0) {
-            elemRef = t.callExpression(t.memberExpression(elemRef, t.identifier("slice")), [t.numericLiteral(i)]);
-          }
+          elemRef = t.callExpression(t.memberExpression(elemRef, t.identifier("slice")), [t.numericLiteral(i)]);
 
           // set the element to the rest element argument since we've dealt with it
           // being a rest already

packages/babel-plugin-transform-es2015-destructuring/test/fixtures/destructuring/issue-5090/exec.js

@@ -0,0 +1,9 @@
+const assign = function([...arr], index, value) {
+  arr[index] = value;
+  return arr;
+}
+
+const arr = [1, 2, 3];
+assign(arr, 1, 42);
+
+assert.deepEqual(arr, [1, 2, 3]);