The attribute export_macro is currently unknown to the compiler

[ctz]

Uh, so I'm being pointed to issue #29642 by current nightly (rustc 1.17.0-nightly (824c9ebbd 2017-03-12)):

error: The attribute `export_macro` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)
 --> src/msgs/macros.rs:3:1
  |
3 | #[export_macro]
  | ^^^^^^^^^^^^^^^
  |
  = help: add #![feature(custom_attribute)] to the crate attributes to enable

src/msgs/macros.rs is:

/// A macro which takes an Option<T> and returns None if it
/// is None, otherwise unwraps().
#[export_macro]
macro_rules! try_ret(
    ($e:expr) => (match $e { Some(e) => e, None => return None })
);

This is extremely strange, because export_macro is documented in the book as being needed for macros to work at all:

Only macros defined with the #[macro_export] attribute may be loaded.

So it can't possibly be the case that it's unknown to the compiler.

With that said, the behaviour doesn't match that documentation -- If I remove export_macro the macro is still loadable from other modules.

[codyps]

#[macro_export] is not the same as #[export_macro].

[ctz]

Oh, how embarrassing. Thanks.