Error when failing to find macro should suggest pub(crate)

[joshtriplett]

Code

mod macros {
    macro_rules! greet {
        () => { println!("Hello, world!"); }
    }

    //pub(crate) use greet;
}

fn main() {
    macros::greet!();
}

Current output

error[E0433]: failed to resolve: could not find `greet` in `module`
  --> src/main.rs:10:13
   |
10 |     module::greet!();
   |             ^^^^^ could not find `greet` in `module`

warning: unused macro definition: `greet`
 --> src/main.rs:2:18
  |
2 |     macro_rules! greet {
  |                  ^^^^^
  |
  = note: `#[warn(unused_macros)]` on by default

Desired output

error[E0603]: macro `greet` is private
  --> src/main.rs:10:13
   |
10 |     module::greet!();
   |             ^^^^^ private macro
   |
note: the macro `greet` is defined here
  --> src/main.rs:2:5
  |
2 |     macro_rules! greet {
  |     ^^^^^^^^^^^^^^^^^^
  = help: consider adding `pub(crate) use greet;` to re-export the macro

(This could be an actual rustfix suggestion, though it should not have high certainty since they may not have intended to use a private macro.)

Rationale and extra context

We already give a better error for attempting to call a private function; this applies the same logic to private macros.

Rust Version

rustc 1.76.0 (07dca489a 2024-02-04)
binary: rustc
commit-hash: 07dca489ac2d933c78d3c5158e3f43beefeb02ce
commit-date: 2024-02-04
host: x86_64-unknown-linux-gnu
release: 1.76.0
LLVM version: 17.0.6

[ChAoSUnItY]

@rustbot claim

[ChAoSUnItY]

@rustbot release-assignment

[veera-sivarajan]

@rustbot claim

[veera-sivarajan]

Sorry, I don't understand macro scoping well enough to work on this.

@rustbot release-assignment