Add the Provider api to core::any

[nrc]

This is an implementation of RFC 3192 (which is yet to be merged, thus why this is a draft PR). It adds an API for type-driven requests and provision of data from trait objects. A primary use case is for the Error trait, though that is not implemented in this PR. The only major difference to the RFC is that the functionality is added to the any module, rather than being in a sibling provide_any module (as discussed in the RFC thread).

Still todo: improve documentation on items, including adding examples.

cc @yaahc

[rust-highfive]

r? @scottmcm

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[bors]

☔ The latest upstream changes (presumably #93548) made this pull request unmergeable. Please resolve the merge conflicts.

[scottmcm]

Sorry for taking a while for getting to this.

While some of the comments I'm confident in, others I'm not tied to at all. As always, feel free to push back on anything you feel differently about.

[nrc]

@scottmcm thanks for the review, they were very useful comments. I think I have addressed the comments, please take another look!

[TimDiekmann]

Clippy gives two suggestions, I added them as a review. 🙂

[nrc]

Comments addressed

[scottmcm]

Thanks for the updates! Things look good to me.

@bors r+

(And sorry for taking a while to rereview after the changes.)

[bors]

📌 Commit 6629010 has been approved by scottmcm

[bors]

⌛ Testing commit 6629010 with merge e9aff9c...

[bors]

☀️ Test successful - checks-actions
Approved by: scottmcm
Pushing e9aff9c to master...

[rust-timer]

Finished benchmarking commit (e9aff9c): comparison url.

Instruction count

• Primary benchmarks: 🎉 relevant improvement found
• Secondary benchmarks: 😿 relevant regression found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	0.3%	0.3%	1
Improvements 🎉 (primary)	-1.0%	-1.0%	1
Improvements 🎉 (secondary)	N/A	N/A	0
All 😿🎉 (primary)	-1.0%	-1.0%	1

Max RSS (memory usage)

Results

• Primary benchmarks: 😿 relevant regression found
• Secondary benchmarks: 🎉 relevant improvements found

	mean1	max	count2
Regressions 😿 (primary)	2.3%	2.3%	1
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-3.0%	-3.8%	3
All 😿🎉 (primary)	2.3%	2.3%	1

Cycles

Results

• Primary benchmarks: no relevant changes found
• Secondary benchmarks: 😿 relevant regression found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	2.1%	2.1%	1
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	N/A	N/A	0
All 😿🎉 (primary)	N/A	N/A	0

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

Footnotes

1. the arithmetic mean of the percent change ↩ ↩² ↩³

2. number of relevant changes ↩ ↩² ↩³