Document From::from impls

[TimTheBig]

This resolves #51430 by documenting all from impls in lib std and core.
I still need someone to look over a few of the comments to see if the style is correct.

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Amanieu (or someone else) some time within the next two weeks.

Please see the contribution instructions for more information. Namely, in order to ensure the minimum review times lag, PR authors and assigned reviewers should ensure that the review label (S-waiting-on-review and S-waiting-on-author) stays updated, invoking these commands when appropriate:

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[rustbot]

The Miri subtree was changed

cc @rust-lang/miri

Portable SIMD is developed in its own repository. If possible, consider making this change to rust-lang/portable-simd instead.

cc @calebzulawski, @programmerjake

rust-analyzer is developed in its own repository. If possible, consider making this change to rust-lang/rust-analyzer instead.

cc @rust-lang/rust-analyzer

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

[TimTheBig]

@rustbot label A-docs C-enhancement T-libs-api

[TimTheBig]

Should I move Portable SIMD and rust-analyzer changes even though they are small?

[RalfJung]

It is generally a good idea to split up large changes. :) You changed a whole bunch of files in rust-analyzer, so yeah that should be split. Miri and clippy have fewer changes, but the fact that there are any changes at all there still contradicts the PR description.

It's too late now, but the best strategy for PRs like this is to start with just a few files, e.g. just core, take the review feedback, and then apply that to the next PRs. That avoids having to re-do large amounts of work when there is overarching feedback.

[rustbot]

The Miri subtree was changed

cc @rust-lang/miri

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

Portable SIMD is developed in its own repository. If possible, consider making this change to rust-lang/portable-simd instead.

cc @calebzulawski, @programmerjake

rust-analyzer is developed in its own repository. If possible, consider making this change to rust-lang/rust-analyzer instead.

cc @rust-lang/rust-analyzer

[TimTheBig]

My mistake, I will revert the rust-analyzer changes.

[oli-obk]

This PR requires a lot of changes, I did not get far with reviews, but a lot of the doc comments only explain the body in its rawest form. I feel like fully reviewing this just makes the reviewer do the work of documenting things, so it may be easier to just write PRs with documentation.

Also please disclose whether you generated this documentation, even just partially or as an initial thing that you edited.