when checking pointee metadata, canonicalize the Sized check

[compiler-errors]

Use infcx.predicate_must_hold_modulo_regions with a Sized obligation instead of just calling ty.is_sized, because the latter does not canonicalize region and type vars (and in the test case I added in this PR, there's a region var in the ParamEnv).

Fixes #95311

[rust-highfive]

r? @matthewjasper

(rust-highfive has picked a reviewer for you, use r? to override)

[bjorn3]

because the latter does not canonicalize region and type vars (and in the test case I added in this PR, there's a region var in the ParamEnv)

Would it make sense to change .is_sized() instead? That may avoid future occurrence of a similar issue.

[compiler-errors]

@bjorn3 that works, but might be a perf regression because we need to do extra canonicalization every call

[dimpolo]

Is anything blocking this?
I would love to switch to a new nightly release 🤓

[compiler-errors]

rolling a new reviewer...

r? rust-lang/compiler

[pnkfelix]

@bors r+ rollup=never

(discussed at T-compiler triage meeting.)

[bors]

📌 Commit 3624f1c has been approved by pnkfelix

[bors]

⌛ Testing commit 3624f1c with merge e7575f9...

[bors]

☀️ Test successful - checks-actions
Approved by: pnkfelix
Pushing e7575f9 to master...

[rust-timer]

Finished benchmarking commit (e7575f9): comparison url.

Summary:

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

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	0	1	0	1	0
mean2	N/A	0.3%	N/A	-0.4%	N/A
max	N/A	0.3%	N/A	-0.4%	N/A

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

@rustbot label: -perf-regression

Footnotes

1. number of relevant changes ↩

2. the arithmetic mean of the percent change ↩