514562 - ES5 strict mode: no assignments to eval

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Jim Blandy :jimb]

From ES5 Appendix C:

The identifier eval may not appear as the LeftHandSideExpression of an Assignment operator   (11.13) or of a PostfixExpression (11.3) or as the UnaryExpression operated upon by a Prefix   Increment (11.4.4) or a Prefix Decrement (11.4.5) operator.

Comment 1

[Jim Blandy :jimb]

Attachment: Forbid assignments to 'eval' in strict mode code.

Comment 3

[Jim Blandy :jimb]

Attachment: Forbid assignments to 'eval' and 'arguments' in strict mode code.

Fold in 'arguments' case.  Although the two are phrased differently in the standard, if one accounts for the erratum on this topic they end up being equivalent.

----

The ES5 spec requires that a TypeError be raised when an assignment to
"arguments" is evaluated in strict function code.  That is, the spec
requires the code:

    function f(x) { 'use strict'; if (x) arguments=1; }
    f(false);

to run without error.

Conversation on es5-discuss determined that this is an error in the
spec, noted in one of the meetings, that never got fixed in the text.

Raising a syntax error at compile time is the proper behavior.

Comment 4

[Jim Blandy :jimb]

Attachment: Forbid assignments to 'eval' and 'arguments' in strict mode code.

Now, with tests.

Comment 5

[Jim Blandy :jimb]

http://hg.mozilla.org/tracemonkey/rev/10046964146a

Comment 6

[:Ms2ger (he/him; ⌚ UTC+1/+2)]

http://hg.mozilla.org/mozilla-central/rev/10046964146a

I suppose this bug is fixed?