Reduce the size of check_attrs.rs and move as much as possible into the attribute parsers.

[JayanAXHF]

As part of the attribute parser rework initiative, i'd be nice to reduce the size of check_attrs.rs and move as much of the code into the attribute parsers themselves. This is part of #131229.

Mentor: @JonathanBrouwer

There is quite a lot of different checks in check_attrs.rs, and the goal is to move as much as possible to the respective attribute parsers. A lot of things are not currently moveable because the right information is not available in the attribute parsers, and making this information available is difficult

All checks:

• check_stability: easy (claimed by @josetorrs) refactor - moving check_stability check to parse_stability #154015
• check_align: easy (claimed by @JayanAXHF) refactor: move check_align to parse_alignment #153189
• check_custom_mir: easy (claimed by @JayanAXHF) refactor(attribute parser): move check_custom_mir to attribute parser #154126
• check_doc_attrs: 1, 3 (partially easy, for example moving the features check for rustc_logo is possible)
• check_inline: 1, 3
• check_loop_match: 1
• check_const_continue: 1
• check_macro_only_attr: 2
• check_rustc_allow_const_fn_unstable: 1
• check_deprecated: 1
• check_target_feature: 2
• check_object_lifetime_default 1
• check_rustc_pub_transparent: 2, 3
• check_naked: 1
• check_track_caller: 1,2
• check_non_exhaustive: 1
• check_ffi_pure: 2
• check_may_dangle: 1, 2
• check_sanitize: 3
• check_link: 1
• check_macro_export: 1
• check_rustc_legacy_const_generics: 1
• check_proc_macro: fundamentally impossible, requires type information
• check_eii_impl: 1
• check_rustc_must_implement_one_of: 1
• check_do_not_recommend: 1
• check_diagnostic_on_unimplemented: 1
• check_diagnostic_on_const: 1

Legend:

1. Requires detailed target information: Requires a way for the target checking to know more about the target than currently available to the attribute parsers. Ideally, we should pass information from either the AST or the HIR down, not sure which is easier.
2. Requires other attrs: These checks check the presence or absence of other attributes. We need to find a nice way to represent this. (claimed by @rperier)
3. The allowed targets depend on the arguments passed to the attribute, we need to find a way to allow target checking to depend on arguments

[JayanAXHF]

@rustbot claim

[JayanAXHF]

Hey @JonathanBrouwer, I'm back home. Would you mind specifying what parts of check_attrs.rs have to be moved and where they have to be moved roughly? I'll get on this soon

[JonathanBrouwer]

This is a very large issue, with a bunch of stuff to do ranging from relatively easy to extremely difficult.

I just scrolled through the check_attr file and one relatively easy one should be to move the check done in the check_align function to parse_alignment in rustc_attr_parsing/src/attributes/repr.rs. Feel free to DM me on zulip if you need more guidance :)

While you do that I'll go through the entire file and make a list of what there is to do

[JayanAXHF]

Thanks for the quick reply! I'll get to doing that, and I'll mark the issue as E-tedious so more people can help