Migrate to tail expression temporary lifetime rule in Edition 2024 #3066
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tracing/src/macros.rs
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| // `valueset_arr` is only suitable as a `match` scrutinee location | ||
| // because the `Value`s assume a very transient temporary lifetime |
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Suggested change
| // `valueset_arr` is only suitable as a `match` scrutinee location | |
| // because the `Value`s assume a very transient temporary lifetime | |
| // `valueset_arr` is need as a `match` scrutinee location. `Value`s | |
| // assume a transient, temporary lifetime. this is necessary to support | |
| // https://github.com/rust-lang/rfcs/pull/3606. |
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Applied with minor edits.
tracing/src/macros.rs
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| macro_rules! valueset { | ||
| // `valueset_arr` is only suitable as a `match` scrutinee location | ||
| // because the `Value`s assume a very transient temporary lifetime | ||
| macro_rules! valueset_arr { |
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why the rename? I would maybe consider keeping it the same name, especially since this is a hidden, semver-exempt API.
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Sure. Rename is reverted.
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@hawkw Thanks for the suggestion. I feel that leaving comments in the macro body would make them stay in the macro expansion, so I took the liberty to lift the explanation to the top of the macro definition. Hopefully this is clear enough to explain the use of |
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Motivation
Related to rust-lang/rust#123739
This is a migration effort to prepare
tracingmacros to be more Edition 2024 oriented.This change is backward-compatible so that the macro works exactly the same in terms of program semantics in both Edition 2018 and prospective Edition 2024.
cc @jieyouxu @traviscross
Solution
valueset!is replaced withvalueset_arr!which must be used at thematchscrutinee location.__tracing_log!macro is written to take a "continuation" so that the&'_ ValueSetis generated and passed into the expanded code only when the logger is enabled.