Make rustc_parse_format compile on stable again

[fmease]

Fixes #115948 (review comment).
cc @Veykril @notriddle

r? compiler

[fmease]

Someday I might open an MCP for #![deny(rustc::features)] or a lang RFC for #![deny(features)] :^)

[est31]

I think a simple PR to add the lint would be enough for that. Lints are explicitly not stable, and this is a lint for an unstable feature (the feature attribute).

[Noratrieb]

can we add a CI builder that builds those crates with the bootstrap compiler (without RUSTC_BOOTSTRAP)?

[fmease]

That's not my metier but I can read up on it.

[fmease]

Can we merge this as is? I think this unblocks the next r-a sync? I'm gonna open a t-bootstrap/t-infra ticket for building crates which ought to compile without unstable features without RUSTC_BOOTSTRAP=1 in CI.

[Noratrieb]

@bors r+

feel free to r- and r=me with an even bigger and scarier warning if you want to

[bors]

📌 Commit 732b4bb has been approved by Nilstrieb

It is now in the queue for this repository.

[fmease]

cc #117937

[bors]

⌛ Testing commit 732b4bb with merge d4559c0...

[bors]

☀️ Test successful - checks-actions
Approved by: Nilstrieb
Pushing d4559c0 to master...

[rust-timer]

Finished benchmarking commit (d4559c0): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.8%	[0.8%, 0.8%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.8%	[-1.2%, -0.6%]	3
Improvements ✅ (secondary)	-2.6%	[-2.6%, -2.6%]	1
All ❌✅ (primary)	-0.4%	[-1.2%, 0.8%]	4

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.7%	[-0.7%, -0.7%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.7%	[-0.7%, -0.7%]	1

Binary size

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

Bootstrap: 674.821s -> 674.873s (0.01%)
Artifact size: 311.10 MiB -> 311.07 MiB (-0.01%)