Const stabilize mem::discriminant

[dtolnay]

Tracking issue: #69821.

This PR is a rebase of #103893 to resolve conflicts in library/core/src/lib.rs (against #102470 and #110393).

[rustbot]

r? @thomcc

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[thomcc]

The implementation is obviously fine. Feel free to r=me once whatever other work needed to approve this is completed.

[dtolnay]

@bors r=thomcc

[bors]

📌 Commit fd207e6 has been approved by thomcc

It is now in the queue for this repository.

[bors]

⌛ Testing commit fd207e6 with merge 06f9d37...

[rust-log-analyzer]

The job armhf-gnu 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

[dtolnay]

@bors retry

[bors]

⌛ Testing commit fd207e6 with merge 7cc36de...

[bors]

☀️ Test successful - checks-actions
Approved by: thomcc
Pushing 7cc36de to master...

[rust-timer]

Finished benchmarking commit (7cc36de): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.3%	[-2.3%, -2.3%]	1
Improvements ✅ (secondary)	-1.2%	[-2.1%, -0.8%]	4
All ❌✅ (primary)	-2.3%	[-2.3%, -2.3%]	1

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.8%	[-0.8%, -0.8%]	1
Improvements ✅ (secondary)	-2.8%	[-5.5%, -1.1%]	14
All ❌✅ (primary)	-0.8%	[-0.8%, -0.8%]	1

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 634.236s -> 635.482s (0.20%)
Artifact size: 304.41 MiB -> 304.41 MiB (0.00%)