Use FnSig instead of raw FnDecl for ForeignItemKind::Fn, fix ICE for Fn trait error on safe foreign fn

[compiler-errors]

Let's use hir::FnSig instead of hir::FnDecl + hir::Safety for ForeignItemKind::Fn. This consolidates some handling code between normal fns and foreign fns.

Separetly, fix an ICE where we weren't handling Fn trait errors for safe foreign fns.

If perf is bad for the first commit, I can rework the ICE fix to not rely on it. But if perf is good, I prefer we fix and clean up things all at once 👍

r? spastorino

Fixes#128764

[compiler-errors]

The only thing I'm concerned about here is the increased size of hir nodes -- but it may not matter since we're arena allocating things anyways.

@bors try @rust-timer queue

[bors]

⌛ Trying commit 2bc54d4 with merge 3f959c8...

[compiler-errors]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 180b795 with merge 9d52643...

[spastorino]

reviewed r=me if perf is good.

[bors]

☀️ Try build successful - checks-actions
Build commit: 9d52643 (9d526439ed68b64802701ddbe9eb0facc2626c34)

[rust-timer]

Finished benchmarking commit (9d52643): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

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

Max RSS (memory usage)

Results (secondary 2.8%)

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)	2.8%	[2.1%, 3.4%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -1.3%)

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
Improvements ✅ (secondary)	-1.3%	[-1.3%, -1.3%]	1
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 760.558s -> 760.505s (-0.01%)
Artifact size: 336.96 MiB -> 336.96 MiB (0.00%)

[compiler-errors]

@bors r=spastorino

[bors]

📌 Commit 2be5599 has been approved by spastorino

It is now in the queue for this repository.

[bors]

⌛ Testing commit 2be5599 with merge 500b05a...

[bors]

💔 Test failed - checks-actions

[bors]

⌛ Testing commit 5635a39 with merge 81068eb...

[bors]

💔 Test failed - checks-actions

[compiler-errors]

@bors retry

[bors]

⌛ Testing commit 5635a39 with merge 6c09136...

[bors]

💔 Test failed - checks-actions

[compiler-errors]

@bors r=spastorino

[bors]

📌 Commit 84633f4 has been approved by spastorino

It is now in the queue for this repository.

[bors]

⌛ Testing commit 84633f4 with merge feeba19...

[bors]

☀️ Test successful - checks-actions
Approved by: spastorino
Pushing feeba19 to master...

[rust-timer]

Finished benchmarking commit (feeba19): comparison URL.

Overall result: ❌✅ regressions and improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.3%	[0.3%, 0.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.5%	[-2.3%, -0.7%]	2
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (secondary -3.3%)

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
Improvements ✅ (secondary)	-3.3%	[-3.7%, -2.5%]	3
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary 2.0%)

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)	2.0%	[2.0%, 2.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 750.326s -> 749.471s (-0.11%)
Artifact size: 339.17 MiB -> 339.10 MiB (-0.02%)