Don't re-intern in with_self_ty if self ty didn't change

[compiler-errors]

No description provided.

[compiler-errors]

@bors2 try @rust-timer queue

[rust-bors]

⌛ Trying commit 9cd4e17 with merge a4f2177…

To cancel the try build, run the command @bors2 try cancel.

[rust-bors]

☀️ Try build successful (CI)
Build commit: a4f2177 (a4f217718b376c59dba20e87f1deb047cdbbf09d)

[rust-timer]

Finished benchmarking commit (a4f2177): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible 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 -1.8%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.8%	[-1.8%, -1.8%]	1
All ❌✅ (primary)	-	-	0

Cycles

Results (primary 1.5%, secondary 2.0%)

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

	mean	range	count
Regressions ❌ (primary)	1.5%	[1.5%, 1.5%]	1
Regressions ❌ (secondary)	2.0%	[2.0%, 2.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[1.5%, 1.5%]	1

Binary size

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

Bootstrap: 751.176s -> 750.253s (-0.12%)
Artifact size: 372.27 MiB -> 372.15 MiB (-0.03%)

[compiler-errors]

I'm surprised this doesn't improve perf, but fine, not worth landing I guess.