Avoid cloning ExpnData to access Span edition

[Mark-Simulacrum]

ExpnData is a fairly hefty structure to clone; cloning it may not be cheap. In
some cases this may get optimized out, but it's not clear that will always be
the case. Try to avoid that cost.

r? @ghost -- opening for a perf run to start with

[Mark-Simulacrum]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[bors]

⌛ Trying commit 7d373c9 with merge df0c4b6e4afe07e7f2ce16b6218d1e8f6634de9c...

[bors]

☀️ Try build successful - checks-actions
Build commit: df0c4b6e4afe07e7f2ce16b6218d1e8f6634de9c (df0c4b6e4afe07e7f2ce16b6218d1e8f6634de9c)

[rust-timer]

Queued df0c4b6e4afe07e7f2ce16b6218d1e8f6634de9c with parent 5aff6dd, future comparison URL.

[rust-timer]

Finished benchmarking try commit (df0c4b6e4afe07e7f2ce16b6218d1e8f6634de9c): comparison url.

Summary: This benchmark run did not return any significant changes.

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.

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

[Mark-Simulacrum]

It does seem like this is a consistent improvement on a number of benchmarks, even if a small one.

r? @petrochenkov perhaps (hopefully a quick approval)

[petrochenkov]

@bors r+

[bors]

📌 Commit 7d373c9 has been approved by petrochenkov

[bors]

⌛ Testing commit 7d373c9 with merge 2155386...

[bors]

☀️ Test successful - checks-actions
Approved by: petrochenkov
Pushing 2155386 to master...