Revert to previous type folding behaviour in an attempt to fix a perf regression

[oli-obk]

Regression occurred in #101858 (comment)

r? @nnethercote

I knew I did a functional change here, but it just seemed wrong to not fold or visit the Ty<'tcx> inside. Let's see if this fixes the perf regression and then we can reevaluate whether the behaviour is correct

[oli-obk]

@bors try @rust-timer queue include=diesel,ctfe-stress-5,tuple-stress

[rust-timer]

Awaiting bors try build completion.

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

[bors]

⌛ Trying commit 8f2fe0f with merge edaec43dbd4ba386300184b22707065380200a20...

[bors]

☀️ Try build successful - checks-actions
Build commit: edaec43dbd4ba386300184b22707065380200a20 (edaec43dbd4ba386300184b22707065380200a20)

[rust-timer]

Queued edaec43dbd4ba386300184b22707065380200a20 with parent 0ee5a1a, future comparison URL.

[rust-timer]

Finished benchmarking commit (edaec43dbd4ba386300184b22707065380200a20): 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-review -S-waiting-on-perf -perf-regression

Instruction count

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

Max RSS (memory usage)

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

Cycles

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

[oli-obk]

damn, that wasn't it.