Prevent creating Instance that proxies another Instance when inferring __new__(cls)

[jacobtylerwalls]

Steps

• For new features or bug fixes, add a ChangeLog entry describing what your PR does.
• Write a good description on what the PR does.

Description

See discussion at pylint-dev/pylint#7109 (comment). When astroid thinks __new__(cls) is being called with an instance either due to user error or because of inference ambiguity (e.g. the library code in the OP used an isinstance guard that astroid doesn't cope with), we now raise InferenceError instead of creating a bogus Instance-proxied-to-Instance. Callers then transform this to Uninferable as appropriate. (See #782 for a precedent.)

Type of Changes

	Type
✓	🐛 Bug fix

Related Issue

Refs pylint-dev/pylint#7109

[coveralls]

Pull Request Test Coverage Report for Build 2602639973

• 8 of 8 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.005%) to 92.109%

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Totals
Change from base Build 2595507463:	0.005%
Covered Lines:	9420
Relevant Lines:	10227

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💛 - Coveralls

[Pierre-Sassoulas]

LGTM, just a question for my information :)

[jacobtylerwalls]

This is going to be too difficult to backport; bumping to 2.12.

[DanielNoord]

Last two nits!

[DanielNoord]

Thanks @jacobtylerwalls!

[jacobtylerwalls]

Thanks for the initial digging and the review! ✨

[Pierre-Sassoulas]

There's two issues left in 2.12, including this one that is mergeable, should we even release 2.11.7 ?

[DanielNoord]

I'd like to get the is None in 2.12 if possible. It was moved to 2.13 recently, but the last reviews don't look like they should take too long to resolve.

[DanielNoord]

This has created an issue for nodes.Const as it can no longer call the __init__ of Instance. We set the ._proxied of Const during bootstrapping.

I'm looking into a solution.

[DanielNoord]

See #1689.