From 28589d459d839bef8af7e03f1d78989dccab528f Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Mon, 13 Apr 2015 16:40:13 -0700
Subject: [PATCH] make illegal LHS pattern error messages more user friendly

---
 src/expression.js | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/expression.js b/src/expression.js
index 998864d077..3540956fe3 100755
--- a/src/expression.js
+++ b/src/expression.js
@@ -103,8 +103,16 @@ 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" || left.type === "ArrayPattern")) {
-      this.raise(left.start, "You're trying to assign to a parenthesized expression, instead of `({ foo }) = {}` use `({ foo } = {})`");
+    if (left.parenthesizedExpression) {
+      let errorMsg
+      if (left.type === "ObjectPattern") {
+        errorMsg = "`({a}) = 0` use `({a} = 0)`"
+      } else if (left.type === "ArrayPattern") {
+        errorMsg = "`([a]) = 0` use `([a] = 0)`"
+      }
+      if (errorMsg) {
+        this.raise(left.start, `You're trying to assign to a parenthesized expression, eg. instead of ${errorMsg}`)
+      }
     }
     this.next()
     node.right = this.parseMaybeAssign(noIn)