Src link for re-exported macros are missing.

[cbreeden]

Consider https://doc.rust-lang.org/core/macro.write.html which has a [Src] link, but https://doc.rust-lang.org/std/macro.write.html does not. The Std docs typically have higher visibility as it's what's linked from the docs.rust-lang.org homepage.

[cbreeden]

One thought I had was to create a exported_macros.html file in the src/ directory of the docs to link to; a place to put the src of the macros and format them.

mbrubeck suggested having rustdoc specifically look at #[macro_reexport(...)] attributes like found here https://doc.rust-lang.org/src/std/up/src/libstd/lib.rs.html#314-318. Perhaps it's possible to then obtain the proper path from the macro for creating a [src] link.