25b21a1d16
Fix invalid special casing of the unreachable! macro This pull-request fix an invalid special casing of the `unreachable!` macro in the same way the `panic!` macro was solved, by adding two new internal only macros `unreachable_2015` and `unreachable_2021` edition dependent and turn `unreachable!` into a built-in macro that do dispatching. This logic is stolen from the `panic!` macro. ~~This pull-request also adds an internal feature `format_args_capture_non_literal` that allows capturing arguments from formatted string that expanded from macros. The original RFC #2795 mentioned this as a future possibility. This feature is [required](https://github.com/rust-lang/rust/issues/92137#issuecomment-1018630522) because of concatenation that needs to be done inside the macro:~~ ```rust $crate::concat!("internal error: entered unreachable code: ", $fmt) ``` **In summary** the new behavior for the `unreachable!` macro with this pr is: Edition 2021: ```rust let x = 5; unreachable!("x is {x}"); ``` ``` internal error: entered unreachable code: x is 5 ``` Edition <= 2018: ```rust let x = 5; unreachable!("x is {x}"); ``` ``` internal error: entered unreachable code: x is {x} ``` Also note that the change in this PR are **insta-stable** and **breaking changes** but this a considered as being a [bug](https://github.com/rust-lang/rust/issues/92137#issuecomment-998441613). If someone could start a perf run and then a crater run this would be appreciated. Fixes https://github.com/rust-lang/rust/issues/92137 |
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