Improve wording of static_mut_ref

[RalfJung]

This lint currently prints

   = note: reference of mutable static is a hard error from 2024 edition
   = note: mutable statics can be written to by multiple threads: aliasing violations or data races will cause undefined behavior

The first line seems grammatically not entirely right to me. Shouldn't it say "in the 2024 edition"? And should it be "reference of" or "reference to"?

The second line doesn't quite capture the problem IMO. The issue is that the reference has lifetime 'static, so

• a mutable reference supposedly lives forever, so creating more than one is very dangerous and they can accidentally be used in overlapping ways
• a shared reference supposedly lives forever, so if there is ever also a mutable reference created that is very dangerous as they can accidentally be used in overlapping ways

Cc @obeis

[obeis]

@rustbot claim

[RalfJung]

Also, the lint should probably be named static_mut_refs. Policy for lints (AFAIK) is for them to have a plural name.

[obeis]

Renaming the lint is not straightforward because of this PR #120676; I am not sure how it can be done.

[RalfJung]

What does that PR have to do with it?

When renaming a lint, remember to register it as a renamed lint. (Though I'm not sure if that will help with whatever issue you were running into.)

[obeis]

I need to allow both lints static_mut_ref and static_mut_refs because Bootstrap will use version 1.77 beta, and static_mut_ref already exists, as I understand.

What do you mean by register it as a renamed lint?

[RalfJung]

I need to allow both lints static_mut_ref and static_mut_refs because Bootstrap will use version 1.77 beta, and static_mut_ref already exists, as I understand.

We have the bootstrap cfg-flag to handle such situations. So you can do something like

#[cfg_attr(bootstrap, allow(static_mut_ref))]
#[cfg_attr(not(bootstrap), allow(static_mut_refs))]

What do you mean by register it as a renamed lint?

rust/compiler/rustc_lint/src/lib.rs

Lines 313 to 326 in cf1096e

	// Register renamed and removed lints.
	store.register_renamed("single_use_lifetime", "single_use_lifetimes");
	store.register_renamed("elided_lifetime_in_path", "elided_lifetimes_in_paths");
	store.register_renamed("bare_trait_object", "bare_trait_objects");
	store.register_renamed("unstable_name_collision", "unstable_name_collisions");
	store.register_renamed("unused_doc_comment", "unused_doc_comments");
	store.register_renamed("async_idents", "keyword_idents");
	store.register_renamed("exceeding_bitshifts", "arithmetic_overflow");
	store.register_renamed("redundant_semicolon", "redundant_semicolons");
	store.register_renamed("overlapping_patterns", "overlapping_range_endpoints");
	store.register_renamed("disjoint_capture_migration", "rust_2021_incompatible_closure_captures");
	store.register_renamed("or_patterns_back_compat", "rust_2021_incompatible_or_patterns");
	store.register_renamed("non_fmt_panic", "non_fmt_panics");
	store.register_renamed("unused_tuple_struct_fields", "dead_code");