outline heavyweight closure that caused regressions in #86898

[the8472]

Testing the suggestion in #86898 (comment)

[rust-highfive]

r? @nagisa

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

[the8472]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[bors]

⌛ Trying commit d878815 with merge ae450c524eac0a8a0226f49bf374b24f9406824f...

[bors]

☀️ Try build successful - checks-actions
Build commit: ae450c524eac0a8a0226f49bf374b24f9406824f (ae450c524eac0a8a0226f49bf374b24f9406824f)

[rust-timer]

Queued ae450c524eac0a8a0226f49bf374b24f9406824f with parent 237bb5e, future comparison URL.

[rust-timer]

Finished benchmarking commit (ae450c524eac0a8a0226f49bf374b24f9406824f): comparison url.

Summary: This change led to small relevant improvements 🎉 in compiler performance.

• Small improvement in instruction counts (up to -0.6% on full builds of issue-46449)

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

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 led to changes in compiler perf.

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

[nagisa]

The nesting is getting quite nasty there, but also waaaaat o.O

@bors r+

[bors]

📌 Commit d878815 has been approved by nagisa

[the8472]

@bors r-

#89031 shows similar results, is more general and has been approved too.