605515 - Strict mode code should throw ReferenceError when assigning to a global if it doesn't exist at BINDNAME time

Status: NEW

(Core :: JavaScript Engine, defect, P3)

Description

[Jason Orendorff [:jorendorff]]

"use strict";
var ok = false;
try {
    undeclared = (this.undeclared = 5);
} catch (exc) {
    ok = exc instanceof ReferenceError;
}
assertEq(ok, true);


Per ES5, this assignment to undeclared should throw a ReferenceError in strict mode. In detail,

    undeclared = (this.undeclared = 5);

* The LHS evaluates to an unresolveable strict Reference (ES5 §10.2.2.1);
* the RHS evaluates to 5;
* assignment to the Reference throws, because it is still
unresolveable (see IsUnresolvableReference, §8.7), even though
undeclared now exists.

Comment 1

[Brendan Eich [:brendan]]

If Allen's fix makes it into an erratum, then there'll be a check before RHS evaluation. But we need a check somewhere.

/be

Comment 2

[David Mandelin [:dmandelin]]

This one's been sitting for a while. ES5 experts, are you guys going to fix this for Fx4?

Comment 3

[Mark S. Miller]

Status?

Comment 4

[Dmitry Soshnikov]

The semantics with checking RHS didn't change in ES6 spec, so this still should throw ReferenceError, because LHS is an unresolved reference.