From beb8061d3fd70f0f60f9f4b08a940873b537972f Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Tue, 21 Jul 2015 18:43:10 +0100
Subject: [PATCH] better identification of strict directives - cc @jmm

---
 packages/babel/src/generation/node/whitespace.js     |  4 ++--
 .../src/transformation/transformers/other/strict.js  | 12 +++++++++++-
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/packages/babel/src/generation/node/whitespace.js b/packages/babel/src/generation/node/whitespace.js
index 0d828ebbcd..6de75c7b1d 100644
--- a/packages/babel/src/generation/node/whitespace.js
+++ b/packages/babel/src/generation/node/whitespace.js
@@ -103,8 +103,8 @@ exports.nodes = {
    * Test if Literal needs whitespace.
    */
 
-  Literal(node) {
-    if (node.value === "use strict") {
+  Literal(node, parent) {
+    if (t.isExpressionStatement(parent)) {
       return {
         after: true
       };
diff --git a/packages/babel/src/transformation/transformers/other/strict.js b/packages/babel/src/transformation/transformers/other/strict.js
index 79467ac27d..07ed970025 100644
--- a/packages/babel/src/transformation/transformers/other/strict.js
+++ b/packages/babel/src/transformation/transformers/other/strict.js
@@ -6,6 +6,16 @@ export var metadata = {
 
 const THIS_BREAK_KEYS = ["FunctionExpression", "FunctionDeclaration", "ClassExpression", "ClassDeclaration"];
 
+function isUseStrict(node) {
+  if (!t.isLiteral(node)) return false;
+
+  if (node.raw && node.rawValue === node.value) {
+    return node.rawValue === "use strict";
+  } else {
+    return node.value === "use strict";
+  }
+}
+
 /**
  * [Please add a description.]
  */
@@ -21,7 +31,7 @@ export var visitor = {
       var first = program.body[0];
 
       var directive;
-      if (t.isExpressionStatement(first) && t.isLiteral(first.expression, { value: "use strict" })) {
+      if (t.isExpressionStatement(first) && isUseStrict(first.expression)) {
         directive = first;
       } else {
         directive = t.expressionStatement(t.literal("use strict"));