`#[doc = compile_error!()]` no longer emits a clean error

[kotauskas]

The following code used to only emit one error (the message passed to compile_error!()) on Rust 1.93, but on Rust 1.94, it emits both the given message and an unhelpful "attribute value must be a literal".

#[doc = compile_error!("my error message")]
fn g() {}

Godbolt link.

I use this in doctest-file to produce errors in a macro meant to be used in #[doc = …] position.

@rustbot modify labels: +regression-from-stable-to-stable -regression-untriaged

[eggyal]

Due to #149645 cc @GuillaumeGomez @JonathanBrouwer @jdonszelmann

[JonathanBrouwer]

@rustbot claim