1127629 - "<blah> is not a function" doesn't work for `void ...` expressions

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Nick Fitzgerald [:fitzgen] [⏰PST; UTC-8]]

When you try and call a variable that is not a function as a function, you get a helpful message:

  > f = undefined
  undefined
  > f()
  TypeError: f is not a function

For some expressions, you get a helpful message too:

  > function getF() {}
  undefined
  > getF()()
  TypeError: getF(...) is not a function

However, if you have a `void ..` expression, then the error message sucks:

  > (void 2)()
  TypeError: undefined is not a function

I'd expect it to be something like "TypeError: (void ...) is not a function".

Are there other cases that produce bad error messages as well?

Comment 1

[Jan de Mooij [:jandem]]

This is the expression decompiler, see ExpressionDecompiler::decompilePC.

It has some generic code for unary and binary operators, but we don't have a token string for JSOP_VOID in Opcodes.h, that's probably why it doesn't work here. If we added one it'd probably decompile to void(2)...

Comment 2

[Tom S [:evilpie]]

Attachment: void-decompile

Or do we always want to decompile, void 0 as `(void 0)`?

Comment 3

[Tom S [:evilpie]]

Attachment: void-decompile

Comment 4

[Jan de Mooij [:jandem]]

Comment on attachment 8567720 [details] [diff] [review]
void-decompile

Review of attachment 8567720 [details] [diff] [review]:
-----------------------------------------------------------------

Nice.

Comment 5

[Tom S [:evilpie]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/2d7d8a404d0a

Comment 6

[Tom S [:evilpie]]

There was some problem with my test and --ion-eager, so I changed it to be more specific.

Comment 7

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/2d7d8a404d0a