Weird help message suggest to place use randomly, when a macro is called in scope

[kennytm]

Repro case (1.19.0-beta.1 as well as nightly):

macro_rules! y {
    () => {}
}
mod m {
    pub const A: i32 = 0;
}
fn main() {
    y!();
    let _ = A;
}

When running it in nightly, it produces a weird error message:

error[E0425]: cannot find value `A` in this scope
 --> 1.rs:9:13
  |
9 |     let _ = A;
  |             ^ not found in this scope
  |
help: possible candidate is found in another module, you can import it into scope
  | fn main() use m::A;

error: aborting due to previous error(s)

No repro on 1.18 or before

error[E0425]: cannot find value `A` in this scope
 --> <source>:9:13
  |
9 |     let _ = A;
  |             ^ not found in this scope
  |
  = help: possible candidate is found in another module, you can import it into scope:
            `use m::A;`
error: aborting due to previous error

Version

rustc 1.19.0-nightly (f062832b2 2017-06-07)
binary: rustc
commit-hash: f062832b208e94f2f0f26ed7fb5c48c172069fbe
commit-date: 2017-06-07
host: x86_64-apple-darwin
release: 1.19.0-nightly
LLVM version: 4.0

[oli-obk]

This is due to #41876

The suggestion placement span is unfortunate. It seems the opening brace belongs to the span of the scope where the import failed. The suggestion should be placed after the opening brace.

I'm not sure why the macro invocation messes up the spans... it works fine without macros

[Mark-Simulacrum]

@oli-obk Do you know why the suggestion puts fn main() in? I'm worried that new users will find that surprising and odd; perhaps we should revert some part (or all of) #41876 for now?

[oli-obk]

The issue only occurs with macros or desugarings at the beginning of the function. I plan a general fix to improve the placement, this should simply get fixed in the process