354921 - Better error messages for destructuring-assignment failures

Status: RESOLVED WORKSFORME

(Core :: JavaScript Engine, enhancement)

Description

[Jesse Ruderman]

({a:{c:x}, b:x}) = ({b:3})
TypeError on line 1: undefined has no properties

[[x]] = 6;
TypeError on line 1: undefined has no properties

I think these could use more specific error messages.

(Split from bug 346642.)

Comment 1

[Jesse Ruderman]

Destructuring arguments could use better error messages, too:

js> (function([y]){})()
typein:1: TypeError: arguments[0] is undefined

Comment 2

[Jesse Ruderman]

The error messages from comment 0 have changed, becoming even more confusing in this context.

js> [[x]] = 6;
typein:2: TypeError: (void 0) is undefined

Comment 3

[Brendan Eich [:brendan]]

Any idea of when this regressed?

/be

Comment 4

[Jesse Ruderman]

I assume it's a combination of bug 375801 and bug 353116, but I haven't tested.

Comment 5

[Luke Wagner [:luke]]

This seems pretty good:

js> ({a:{c:x}, b:x}) = ({b:3})
typein:14:1 TypeError: (intermediate value).a is undefined
js> [[x]] = 6;
typein:15:0 TypeError: 6[0] is undefined