Ensure preserveToString doesn't error out if provided an invalid `s…

…ource`.
paulmillr · Oct 23, 2015 · caa4463 · caa4463
1 parent 30f4bde
commit caa4463
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/es6-shim.js b/es6-shim.js
@@ -207,7 +207,9 @@
       }
     },
     preserveToString: function (target, source) {
-      defineProperty(target, 'toString', source.toString.bind(source), true);
+      if (source && ES.IsCallable(source.toString)) {
+        defineProperty(target, 'toString', source.toString.bind(source), true);
+      }
     }
   };