Unergonomic pub(in path) error message

[est31]

The pub(in path) error message is very unergonomic when it comes to paths that don't exist, or don't exist yet. Take this example, its how the error was intented:

pub mod baa {}
pub mod boo {
	pub (in baa) fn foo() {}
}

gives an error "visibilities can only be restricted to ancestor modules". Now take this example:

pub mod boo {
	pub (in baa) fn foo() {}
}
pub mod baa {}

This gives an error "cannot find module baa in the crate root".

And this code:

pub mod boo {
	pub (in baa::baa) fn foo() {}
}

even gives an error "failed to resolve. Maybe a missing extern crate baa;?".

What should happen instead is that in the second and third case, it should output an error similar to the first one. As it seems to not know about modules declared after the code yet (see second case), adding a note to the existing error is not enough, as clearly an error "cannot find module baa in the crate root" is misleading in this case. So unless it can be taught to know modules declared after the current code, I'd suggest to have an error similar to the first case in all three cases.

[est31]

Seems this is already pointed out in src/test/compile-fail/resolve-bad-visibility.rs. Still, I consider this a bug.

[petrochenkov]

Duplicate of #40066