Make from{,_mut}_ptr_range const

[WaffleLapkin]

This PR makes the following APIs const:

// core::slice

pub const unsafe fn from_ptr_range<'a, T>(range: Range<*const T>) -> &'a [T];
pub const unsafe fn from_mut_ptr_range<'a, T>(range: Range<*mut T>) -> &'a mut [T];

Tracking issue: #89792.
Feature for from_ptr_range as a const fn: slice_from_ptr_range_const.
Feature for from_mut_ptr_range as a const fn: slice_from_mut_ptr_range_const.

r? @oli-obk

[rust-highfive]

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with r? rust-lang/libs-api @rustbot label +T-libs-api -T-libs to request review from a libs-api team reviewer. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

• Stabilizing library features
• Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
• Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
• Changing public documentation in ways that create new stability guarantees
• Changing observable runtime behavior of library APIs

[WaffleLapkin]

@rustbot label +T-libs-api -T-libs

[oli-obk]

@bors r+ rollup

[bors]

📌 Commit 70fe652c8945e73effbddf840309d40eab91988b has been approved by oli-obk

[oli-obk]

@bors r-

Please add a test showing some uses of these functions from within const contexts

[WaffleLapkin]

@oli-obk should it be a documentation test or where should I place it?

[oli-obk]

Maybe wherever from_raw_parts is tested? I think there are some ui tests for when it errors and for when it succeeds

[WaffleLapkin]

I haven't found any. All tests that mention slice::from_raw_parts (issue-76387-llvm-miscompile.rs, slice-of-zero-size-elements.rs, issue-76387.rs, const-size_of_val-align_of_val.rs, issue-91827-extern-types.rs, issue-36474.rs, method-mut-self-modifies-mut-slice-lvalue.rs, unsized3-rpass.rs) seem to test something else.

[oli-obk]

That's not great, we should test the failure paths for all of these. Please add a new ui test that creates all kinds of bogus slices at compile time and puts them in the final value of a constant or static

[WaffleLapkin]

Turns out coming out with bogus slices is not that simple, I have problems with my imagination xD

I've added UI tests and also fixed the reexport and feature name.

[WaffleLapkin]

I do not understand why CI is failing, locally the test passes just fine :(

[oli-obk]

The test is failing on 32 bit systems. You can either emit stderr per bitsize (there's a modifier comment for that) or disable the test on 32 bit. Either wfm, tho the former seems better for coverage. If you do the former you'll have to bless for 32 bit, too. You can do this by passing --target=foo to your x.py command with a 32 bit platform that you can build for locally (for me that is i686-unknown-linux-gnu). If you get random other test failures, those'll be run-pass tests that fail because you can't execute those (happens for me when testing run pass against an apple target)

[oli-obk]

@bors r+

[bors]

📌 Commit 3414c03 has been approved by oli-obk

[WaffleLapkin]

            ╾─a79+0x1─╼ 04 00 00 00                         │ ╾──╼....

why is it just a in this case...

Anyway, I've normalized some more, maybe this time I've fixed all problems?

[compiler-errors]

Let's try it.

@bors r=oli-obk

[bors]

📌 Commit 3a2bb78 has been approved by oli-obk

[bors]

⌛ Testing commit 3a2bb78 with merge b7cb2e9f17d546601b4f7276f2c1315261b04b44...

[rust-log-analyzer]

The job dist-x86_64-apple-alt failed! Check out the build log: (web) (plain)

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

[bors]

💔 Test failed - checks-actions

[WaffleLapkin]

warning: spurious network error (2 tries remaining): [28] Timeout was reached (download of petgraph v0.5.1 failed to transfer more than 10 bytes in 30s)
warning: spurious network error (2 tries remaining): [28] Timeout was reached (failed to download any data for jemalloc-sys v0.5.0+5.3.0 within 30s)
warning: spurious network error (2 tries remaining): [28] Timeout was reached (download of scoped-tls v1.0.0 failed to transfer more than 10 bytes in 30s)
warning: spurious network error (2 tries remaining): [28] Timeout was reached (failed to download any data for rls-data v0.19.1 within 30s)
Downloaded rls-data v0.19.1
warning: spurious network error (1 tries remaining): [28] Timeout was reached (download of jemalloc-sys v0.5.0+5.3.0 failed to transfer more than 10 bytes in 30s)
warning: spurious network error (1 tries remaining): [28] Timeout was reached (failed to download any data for petgraph v0.5.1 within 30s)
error: failed to download from [https://crates.io/api/v1/crates/jemalloc-sys/0.5.0+5.3.0/download](https://crates.io/api/v1/crates/jemalloc-sys/0.5.0+5.3.0/download%60)

[compiler-errors]

@bors retry spurious network issue

[bors]

⌛ Testing commit 3a2bb78 with merge 0a43923...

[bors]

☀️ Test successful - checks-actions
Approved by: oli-obk
Pushing 0a43923 to master...

[WaffleLapkin]

Yay 🎉

[WaffleLapkin]

Oh no, I messed up the feature gate

[rust-timer]

Finished benchmarking commit (0a43923): comparison url.

Instruction count

• Primary benchmarks: no relevant changes found
• Secondary benchmarks: mixed results

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	1.1%	1.1%	3
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-0.2%	-0.2%	1
All 😿🎉 (primary)	N/A	N/A	0

Max RSS (memory usage)

Results

• Primary benchmarks: 😿 relevant regression found
• Secondary benchmarks: 😿 relevant regressions found

	mean1	max	count2
Regressions 😿 (primary)	2.5%	2.5%	1
Regressions 😿 (secondary)	2.2%	3.0%	2
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	N/A	N/A	0
All 😿🎉 (primary)	2.5%	2.5%	1

Cycles

Results

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

	mean1	max	count2
Regressions 😿 (primary)	2.8%	2.8%	1
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	N/A	N/A	0
All 😿🎉 (primary)	2.8%	2.8%	1

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