Validate fluent variable references in tests

[clubby789]

Closes #101109

Under cfg(test), the fluent_messages macro will emit a list of variables referenced by each message and its attributes. The derive attribute will now emit a #[test] that checks that each referenced variable exists in the structure it's applied to.

[rustbot]

r? @davidtwco

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[rustbot]

rustc_macros::diagnostics was changed

cc @davidtwco, @compiler-errors, @JohnTitor, @TaKO8Ki

[clubby789]

Hmm, doesn't work right now if the message is part of a subdiagnostic that defines the variable.
I'll exclude structs with subdiagnostics for now, then fix and add tests for the existing errors

[cjgillot]

Why gate on debug_assertions? The only code changes are in macros and generated unit tests, so there is nothing that make the runtime slower.

[clubby789]

I didn't want to have the macro always generate code that would only be used in tests. I guess I could instead just make sure that everything emitted by the macro is cfg(test)'d

[davidtwco]

Apologies for the delay in reviewing here - I like this, but is it possible to add a test for these new tests? Something that confirms a diagnostic struct without the correct variables will have an error?

[davidtwco]

@bors r+

[bors]

📌 Commit 8969d97 has been approved by davidtwco

It is now in the queue for this repository.

[bors]

⌛ Testing commit 8969d97 with merge 08fd6f7...

[bors]

☀️ Test successful - checks-actions
Approved by: davidtwco
Pushing 08fd6f7 to master...

[rust-timer]

Finished benchmarking commit (08fd6f7): 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)	1.3%	[1.3%, 1.3%]	1
Regressions ❌ (secondary)	2.8%	[2.8%, 2.8%]	1
Improvements ✅ (primary)	-3.5%	[-4.5%, -2.5%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.9%	[-4.5%, 1.3%]	3

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)	1.9%	[1.1%, 3.2%]	4
Regressions ❌ (secondary)	5.2%	[2.4%, 9.4%]	12
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.9%	[1.1%, 3.2%]	4

Binary size

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

Bootstrap: 662s -> 662.942s (0.14%)