#![warn(trivial_numeric_casts)] stays cached when commenting out or uncommenting

[martin-t]

Starting with this code:

#![warn(trivial_numeric_casts)]

fn main() {
    println!("{}", 0u8 as u8);
}

and running cargo build, it correctly warns:

warning: trivial numeric cast: `u8` as `u8`. Cast can be replaced by coercion, this might require type ascription or a temporary variable
 --> src/main.rs:4:20
  |
4 |     println!("{}", 0u8 as u8);
  |                    ^^^^^^^^^
  |
note: lint level defined here
 --> src/main.rs:1:9
  |
1 | #![warn(trivial_numeric_casts)]
  |         ^^^^^^^^^^^^^^^^^^^^^

Then I comment out the warn setting as //#![warn(trivial_numeric_casts)] and run cargo build again but it still warns:

warning: trivial numeric cast: `u8` as `u8`. Cast can be replaced by coercion, this might require type ascription or a temporary variable
 --> src/main.rs:4:20
  |
4 |     println!("{}", 0u8 as u8);
  |                    ^^^^^^^^^
  |
note: lint level defined here
 --> src/main.rs:1:9
  |
1 | //#![warn(trivial_numeric_casts)]
  |         ^^^^^^^^^^^^^^^^^^^^^

The underline is off as if the // wasn't there.

Changing the code in any way (e.g. 1u8) probably invalidates the cache because the warnings disappear.

Tested on rustc 1.27.1 (5f2b325f6 2018-07-07) and rustc 1.29.0-nightly (254f8796b 2018-07-13).

[Enselic]

Triage: I can't reproduce this any longer. Can you?

[martin-t]

Tested on 1.76 nightly and it no longer happens so it probably got fixed at one point. Thanks for checking up on the issue. Closing.