From 6cc0538d2ff058e7a1a238433254d1d637713f87 Mon Sep 17 00:00:00 2001
From: Victor Felder <victorfelder@gmail.com>
Date: Wed, 16 Dec 2015 15:41:43 +0100
Subject: [PATCH] Safely transform all usages of rest arguments

---
 .../src/rest.js                                    | 14 +-------------
 .../fixtures/parameters/rest-multiple/actual.js    |  5 +++--
 .../fixtures/parameters/rest-multiple/expected.js  |  5 +++--
 3 files changed, 7 insertions(+), 17 deletions(-)

diff --git a/packages/babel-plugin-transform-es2015-parameters/src/rest.js b/packages/babel-plugin-transform-es2015-parameters/src/rest.js
index f544232b42..2df03de411 100644
--- a/packages/babel-plugin-transform-es2015-parameters/src/rest.js
+++ b/packages/babel-plugin-transform-es2015-parameters/src/rest.js
@@ -121,23 +121,11 @@ export let visitor = {
     argsId._shadowedFunctionLiteral = path;
 
     function optimiseCandidate(parent, parentPath, offset) {
-      if (t.isReturnStatement(parentPath.parent) || t.isIdentifier(parentPath.parent.id) || t.isIdentifier(parentPath.parent.left)) {
+      if (parent.property) {
         parentPath.replaceWith(loadRest({
           ARGUMENTS: argsId,
           INDEX: t.numericLiteral(parent.property.value + offset)
         }));
-      } else {
-        if (offset === 0) return;
-        let newExpr;
-        let prop = parent.property;
-
-        if (t.isLiteral(prop)) {
-          prop.value += offset;
-          prop.raw = String(prop.value);
-        } else { // UnaryExpression, BinaryExpression
-          newExpr = t.binaryExpression("+", prop, t.numericLiteral(offset));
-          parent.property = newExpr;
-        }
       }
     }
 
diff --git a/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-multiple/actual.js b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-multiple/actual.js
index c0f61ede0d..4ece5d67d3 100644
--- a/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-multiple/actual.js
+++ b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-multiple/actual.js
@@ -13,6 +13,7 @@ function t(f, ...items) {
 function u(f, g, ...items) {
     var x = f;
     var y = g;
-    x = items[0];
-    y = items[1];
+    x[12] = items[0];
+    y.prop = items[1];
+    var z = items[2] | 0 || 12;
 }
diff --git a/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-multiple/expected.js b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-multiple/expected.js
index a8d86df09f..2e36f99a60 100644
--- a/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-multiple/expected.js
+++ b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-multiple/expected.js
@@ -13,6 +13,7 @@ function t(f) {
 function u(f, g) {
     var x = f;
     var y = g;
-    x = arguments.length <= 2 ? undefined : arguments[2];
-    y = arguments.length <= 3 ? undefined : arguments[3];
+    x[12] = arguments.length <= 2 ? undefined : arguments[2];
+    y.prop = arguments.length <= 3 ? undefined : arguments[3];
+    var z = (arguments.length <= 4 ? undefined : arguments[4]) | 0 || 12;
 }