Undocumented Attributes #532

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1. Centril

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   EnhancementImprovement in a non-prose section of the bookImprovement in a non-prose section of the book

   on Mar 8, 2019
2. petrochenkov commented on Mar 8, 2019

   

   petrochenkov

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   automatically_derived is also an implementation detail, I don't know why it's not feature gated.
3. Centril commented on Mar 8, 2019

   

   Centril

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   automatically_derived — I vote "probably"? It has some use in the wild. I think the only reason to use it is for rustdoc. Are there other reasons to use it?

   What does the attribute do?

   @petrochenkov Could you try a PR + crater to "destabilization"?

   bench — I vote "no". It requires the unstable Bencher to be used.

   👍

   feature — I vote "maybe" 🤔? Although this is a nightly-oriented attribute, it is very widely used.

   👍 + note that it is unstable.

   reexport_test_harness_main — I vote "no". Even though it is usable on stable, I think it is an internal implementation detail, and I do not see anyone using it.

   What... @petrochenkov I'd also attempt destabilization for this...

   type_length_limit — I vote "yes". I think it is analogous to recursion_limit, and I suspect it just fell through the cracks.

   Sounds good.

   These are just waiting to be finished:

   @ehuss I think these PRs haven't received any attention for some time, if you would like to take over them that'd be nice.
4. ehuss commented on Mar 8, 2019

   

   ehuss

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   What does the attribute do?

   Hm, looking closer, I'm not sure. rustdoc used to use it to separate automatically derived traits, but it was removed in rust-lang/rust#34105. Just grepping through the code shows a few uses:

   • Avoids unused warnings.
   • Something about unsafety checks.
   • Clippy uses it for some lints.

   Here's a sampling of crates that use it in the wild:

   • alga_derive
   • aster
   • bart_derive
   • bit_manager_derive
   • clippy_lints
   • drop-take-derive
   • enum-kinds
   • enum-kinds-macros
   • enum-map-derive
   • enum_traits_macros
   • eosio_macros
   • gluon_codegen
   • log4rs-rolling-file
   • nue-codegen
   • palette_derive
   • runtime-fmt-derive
   • serde_codegen
   • serde_derive
   • serde_derive_state
   • serde_yaml_incomplete

   if you would like to take over them that'd be nice.

   Yea, I'll try to take a look. I think Jorge said he's busy with thesis work.
5. Centril commented on Mar 8, 2019

   

   Centril

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   Something about unsafety checks.

   That sounds concerning...

   Here's a sampling of crates that use it in the wild:

   Oh... wow; That seems quite unfortunate... Might be unfeasible to destabilize, maybe we should try to clarify semantics instead then...
6. ehuss commented on Mar 8, 2019

   

   ehuss

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   That sounds concerning...

   Here it is used to display a warning diagnostic if #[derive] is used on something that uses #[repr(packed)] that doesn't implement Copy. Seems a bit presumptuous that all derives will do something unsafe, but I'm not going to read the long discussion where it was introduced (rust-lang/rust#44884). SAFE_PACKED_BORROWS says it will become a hard error in the future.
7. ehuss

   added

   A-attributesArea: AttributesArea: Attributes

   on Mar 11, 2019
8. Havvy commented on Aug 19, 2020

   

   Havvy

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   This can be closed, yes?
9. ehuss commented on Aug 19, 2020

   

   ehuss

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   Yea. I seem to recall leaving it open for some reason, but now I can't remember.
10. ehuss

    closed this as completedon Aug 19, 2020