added core::mem::reshape

[hazelwiss]

tracking issue: #130848

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[rust-log-analyzer]

The job mingw-check failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

#16 2.838 Building wheels for collected packages: reuse
#16 2.839   Building wheel for reuse (pyproject.toml): started
#16 3.090   Building wheel for reuse (pyproject.toml): finished with status 'done'
#16 3.091   Created wheel for reuse: filename=reuse-4.0.3-cp310-cp310-manylinux_2_35_x86_64.whl size=132715 sha256=dfa09868353292d98f811d3efdb0d54d07389e808efc71d68e3b93c514bf8bec
#16 3.091   Stored in directory: /tmp/pip-ephem-wheel-cache-fnbbmtkz/wheels/3d/8d/0a/e0fc6aba4494b28a967ab5eaf951c121d9c677958714e34532
#16 3.094 Installing collected packages: boolean-py, binaryornot, tomlkit, reuse, python-debian, markupsafe, license-expression, jinja2, chardet, attrs
#16 3.485 Successfully installed attrs-23.2.0 binaryornot-0.4.4 boolean-py-4.0 chardet-5.2.0 jinja2-3.1.4 license-expression-30.3.0 markupsafe-2.1.5 python-debian-0.1.49 reuse-4.0.3 tomlkit-0.13.0
#16 3.486 WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
#16 DONE 3.6s

[Noratrieb]

this is not sound if f unwinds, as the value will be dropped twice. see https://docs.rs/replace_with/latest/replace_with/ for details. the design space here is nontrivial, as there are many possible behaviors to do on unwind. this should at least go through an ACP, but probably better for more general discussion on internals.rust-lang.org. i'd also suggesting searching there for previous discussion about "replace_with", which is what this function is generally called

[hazelwiss]

yeah I just detected that myself and ran into a wall. Sounds good 👍

[hazelwiss]

has there been any discussion about a feature to ensure a closure does not panic?

[Noratrieb]

hm. this has probably come up in vague ways in many places but nothing concrete.

[Noratrieb]

either way it's definitely both that will arrive any time soon, so it probably makes sense to close the PR and tracking issue for now

[Noratrieb]

thank you for it anyways :3

[hazelwiss]

👍

[juntyr]

Could you execute the closure inside an extern "C" wrapper func that would abort on unwind? I think I recently saw a PR on a helper that exposed abort on unwind (mirroring the catch_unwind function) using that technique

[workingjubilee]

You're thinking of #130339

[narpfel]

Suggested change

	/// mem::replace(&mut v, |mut v| { v.push(3); v });
	/// mem::reshape(&mut v, |mut v| { v.push(3); v });

Should this be reshape?

[bjorn3]

I don't think this is a good name. When I first came across the tracking issue in the issue list, I though this was something transmute related.