1665746 - TypeError: iterable is not iterable

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect, P3)

Description

[Pomax]

Attachment: screenshot.333.png

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:82.0) Gecko/20100101 Firefox/82.0

Steps to reproduce:

var a = new Set([1,2,3]);
var b = new Set([2,3,4]);
var c = new Set(...a, ...b);

Actual results:

This throws an error "Uncaught TypeError: iterable is not iterable", which is quite impressive

Expected results:

A TypeError that wasn't self-contraditory. The Set constructor takes a single argument, which must be an iterable, so if you call it as new Set(1) you get an error that makes sense:

"Uncaught TypeError: 1 is not iterable"

But it seems to not actually report on the true argument when deferencing: it feels like it's trying to report on the construction ...input itself, rather than on what that actually turns into (namely, single elements).

Note that this will not happen for something like new Set('a', 'b', 'c') or new Set(...['a','b','c']) as strings are iterable. You'll just get a single element Set containing just a in both cases.

Comment 2

[Tooru Fujisawa [:arai]]

it's using the following variable name for reporting
https://searchfox.org/mozilla-central/rev/5efefd3ef214ed6d3234ba245c1da3004ead94e0/js/src/builtin/Set.js#18

function SetConstructorInit(iterable) {
...
   for (var nextValue of allowContentIter(iterable))

fix would be either:

• use more descriptive variable name there
• do not use decompiler for self-hosted JS code

Comment 3

[Tooru Fujisawa [:arai]]

the same happens for WeakSet.
https://searchfox.org/mozilla-central/rev/5efefd3ef214ed6d3234ba245c1da3004ead94e0/js/src/builtin/WeakSet.js#7-18

Comment 4

[Tooru Fujisawa [:arai]]

We already have a logic that tries to get arguments, but if it fails, it prints parameter name.
https://searchfox.org/mozilla-central/rev/5efefd3ef214ed6d3234ba245c1da3004ead94e0/js/src/vm/BytecodeUtil.cpp#1782-1808

we should instead abort decompiler for this case.

Comment 5

[Tooru Fujisawa [:arai]]

Attachment: Bug 1665746 - Do not use self-hosted JS parameter name in decompiler. r?evilpie!

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/f50e7b70132a
Do not use self-hosted JS parameter name in decompiler. r=evilpie

Comment 7

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/f50e7b70132a