Need more helpful warning when "pub extern" function is not exported via "pub use"

[federicomenaquintero]

I'm creating a bunch of #[no_mangle] pub extern fn that will be callable from C code. Sometimes I forget to put them in my toplevel lib.rs as pub use. This is the warning I get:

warning: function is marked #[no_mangle], but not exported
   --> src/state.rs:436:1
    |
436 |   pub extern "C" fn rsvg_state_rust_parse_style_pair(
    |   ^
    |   |
    |  _help: try making it public: `pub `

At first sight, that function is already pub! The warning should say that I need to export it from the crate via pub use.

[zackmdavis]

This should be fixed on nightly and in 1.25: #47479

[zackmdavis]

Or rather, the bogus suggestion to add pub when it already says pub has been fixed, but we don't yet have the correct pub use suggestion.

[federicomenaquintero]

I'm trying my hand at a fix for this. It's my first contribution to the compiler 😛 What would be appropriate wording for the hint - something like try exporting it in your crate's toplevel: pub use fully:qualified:id_name;?

[zackmdavis]

@federicomenaquintero Sorry no one got around to answering your question back in March. A note suggesting exporting with pub use was added in 8d1cbb0, so I think this issue can be closed.

[federicomenaquintero]

No problem; thanks for the notice 😄