The documented patterns for some compiler builtin macros are subtly incorrect

[ExpHP]

Example: The macro env is documented as

macro_rules! env {
    ($name:expr) => { ... };
}

when in reality, the following call is legal (playground):

let e = env!("PATH",); // <- Note: Trailing comma

I believe this is because the definition in std is just a fake stub. concat! and concat_idents! (edit: also format_args!) are in a similar boat (they also support trailing commas in places where the documented pattern suggests they would not).

In all fairness this is not a big deal, and even has the conceivable benefit that the documentation is cleaner without such laser precision. I just thought it was worth making an issue for.

[steveklabnik]

this is not a big deal

it's all good! These should be correct. Happy to take PRs.

[ExpHP]

closing since fix was merged