1611876 - Wrong message for TypeError

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect, P2)

Description

[_]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:74.0) Gecko/20100101 Firefox/74.0

Steps to reproduce:

I executed:

a = {}
b = {}
a.c.d = b.e

Tested on 74.0a1 (2020-01-27) (64-bit) on Fedora 31.

Actual results:

I got the error: TypeError: can't access property "d", b.e is undefined

Expected results:

I expect the error: TypeError: can't access property "d", a.c is undefined

Comment 1

[_]

Another example, which gives an expected error message is:

a = {}
b = {}
a.c.d = ""

It gives the error message: TypeError: can't access property "d", a.c is undefined

Comment 2

[Tooru Fujisawa [:arai]]

This is caused by the confusion between 2 undefined values on the stack, while decompiling the value for error report.
in the example code, b.e is also undefined and is top of the stack, so DecompileValueGenerator finds it and returns decompiled string for it.

we might be able to specify where to search in the stack, depending on the current operation.

Comment 3

[Tooru Fujisawa [:arai]]

Attachment: Bug 1611876 - Specify the stack index for decompilation when reporting null or undefined property access. r?jwalden

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/fc5a0b479615
Specify the stack index for decompilation when reporting null or undefined property access. r=jwalden

Comment 5

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/fc5a0b479615