121201 2013-09-11 19:06:14 -0700 Invalid exception trying to set property on primitive value in strict mode 2013-09-12 10:10:56 -0700 1 1 1 Unclassified WebKit JavaScriptCore 528+ (Nightly build) Unspecified Unspecified NEW P2 Normal --- 1 arv oliver barraclough ggaren oldest_to_newest 928096 0 arv 2013-09-11 19:06:14 -0700 The following throws an exception in JSC but works correctly in V8, SpiderMonkey and Chakra: function f() { 'use strict'; 1 .foo = 'bar' } f(); Here are the relevant spec parts: http://people.mozilla.org/~jorendorff/es6-draft.html#sec-12.2.1 MemberExpression : MemberExpression [ Expression ] 1. Let baseReference be the result of evaluating MemberExpression. 2. Let baseValue be GetValue(baseReference). ... 10. If the code matched by the syntactic production that is being evaluated is strict mode code, let strict be true, else let strict be false. 11. Return a value of type Reference whose base value is bv and whose referenced name is propertyNameString, and whose strict reference flag is strict. http://people.mozilla.org/~jorendorff/es6-draft.html#sec-6.2.4.2 PutValue (V, W) 5 is false, 6 is true, 6a is true. /base/ becomes ToObject(base) which is an object wrapper of the primitive. 6b calls [[Set]] which does not fail (the object wrapper is extensible) 928354 1 oliver 2013-09-12 09:56:13 -0700 Reading the spec to determine if this is correct behaviour or not. It should be easy to fix if not.