Replace most Ty::new_fn_def calls with type_of queries directly

[addiesh]

This is so we can reduce the amount of code and changes in #159403. It should stand on its own, but really it's meant as an extended part of 159403.

This allows getting the right ty::FnDef even cross-crate, as the type_of query results are stored in metadata, in contrast to the queries for computing the binder for various declarations. These binders are already cached via fn_sig, but using that is somewhat overkill and can cause cycle errors in some cases.

[rustbot]

Thanks for the pull request, and welcome! The Rust Project is excited to review your changes, and you should hear from @oli-obk (or someone else) some time within the next two weeks.

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[addiesh]

i wish github supported funnier reactions for PRs so I could 😭 when CI fails

[oli-obk]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 221275a (221275a593e1700a6824feb1f05823991afce3f1)
Base parent: f65b272 (f65b272fc92b1e7527dea4a224430a249ab25c2d)

[rust-timer]

Finished benchmarking commit (221275a): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking means the PR may be perf-sensitive. Consider adding rollup=never if this change is not fit for rolling up.

@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

This perf run didn't have relevant results for this metric.

Max RSS (memory usage)

Results (primary 1.7%, secondary -0.1%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.7%	[1.7%, 1.7%]	1
Regressions ❌ (secondary)	3.8%	[2.5%, 5.0%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.7%	[-4.0%, -1.5%]	3
All ❌✅ (primary)	1.7%	[1.7%, 1.7%]	1

Cycles

This perf run didn't have relevant results for this metric.

Binary size

Results (primary 0.0%, secondary 0.0%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	4
Regressions ❌ (secondary)	0.0%	[0.0%, 0.1%]	16
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	4

Bootstrap: 487.415s -> 487.919s (0.10%)
Artifact size: 387.80 MiB -> 387.86 MiB (0.02%)

[rustbot]

HIR ty lowering was modified

cc @fmease

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

Some changes occurred in match lowering

cc @Nadrieril

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[addiesh]

@rustbot ready

[oli-obk]

@bors delegate+

r=me with commit message matching the PR message

View changes since this review

[rust-bors]

✌️ @addiesh, you can now approve this pull request!

If @oli-obk told you to "r=me" after making some further change, then please make that change and post @bors r=oli-obk.

View changes since this delegation.

[rustbot]

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.