make parenthesized array patterns illegal - cc @michaelficarra

src/acorn/src/expression.js

@@ -103,7 +103,7 @@ pp.parseMaybeAssign = function(noIn, refShorthandDefaultPos, afterLeftParse) {
     node.left = this.type === tt.eq ? this.toAssignable(left) : left
     refShorthandDefaultPos.start = 0 // reset because shorthand default was used correctly
     this.checkLVal(left)
-    if (left.parenthesizedExpression && left.type === "ObjectPattern") {
+    if (left.parenthesizedExpression && (left.type === "ObjectPattern" || left.type === "ArrayPattern")) {
       this.raise(left.start, "You're trying to assign to a parenthesized expression, instead of `({ foo }) = {}` use `({ foo } = {})`");
     }
     this.next()

test/acorn/tests-babel.js

@@ -2,6 +2,14 @@ var test = require("./driver.js").test;
 var testFail = require("./driver.js").testFail;
 var testAssert = require("./driver.js").testAssert;
 
+testFail("({a}) = 2;", "You're trying to assign to a parenthesized expression, instead of `({ foo }) = {}` use `({ foo } = {})` (1:1)", {
+  ecmaVersion: 6
+});
+
+testFail("([a]) = 2;", "You're trying to assign to a parenthesized expression, instead of `({ foo }) = {}` use `({ foo } = {})` (1:1)", {
+  ecmaVersion: 6
+});
+
 // ES7: Exponentiation Operator
 
 test('a **= 2;', {