Incorrect path in E0004 match suggestion for enum from another module

[makai410]

Code

pub mod cat {
    pub enum Meow {
        Foo,
    }
}
fn main() {
    let v = cat::Meow::Foo;
    match v {}
}

Current output

error[E0004]: non-exhaustive patterns: `Meow::Foo` not covered
 --> src/main.rs:8:11
  |
8 |     match v {}
  |           ^ pattern `Meow::Foo` not covered
  |
note: `Meow` defined here
 --> src/main.rs:2:14
  |
2 |     pub enum Meow {
  |              ^^^^
3 |         Foo,
  |         --- not covered
  = note: the matched value is of type `Meow`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
  |
8 ~     match v {
9 +         Meow::Foo => todo!(),
10~     }
  |

For more information about this error, try `rustc --explain E0004`.
error: could not compile `playground` (bin "playground") due to 1 previous error

Desired output

error[E0004]: non-exhaustive patterns: `Meow::Foo` not covered
 --> src/main.rs:8:11
  |
8 |     match v {}
  |           ^ pattern `Meow::Foo` not covered
  |
note: `Meow` defined here
 --> src/main.rs:2:14
  |
2 |     pub enum Meow {
  |              ^^^^
3 |         Foo,
  |         --- not covered
  = note: the matched value is of type `Meow`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
  |
8 ~     match v {
9 +         cat::Meow::Foo => todo!(),
10~     }
  |

For more information about this error, try `rustc --explain E0004`.
error: could not compile `playground` (bin "playground") due to 1 previous error

Rationale and extra context

I think there should be a discussion about whether the path should be in front of the name of the enum. Anyway, the code suggestion is wrong because it will cause an error if we apply it.

Other cases

Rust Version

playground(1.87.0-nightly (2025-02-28 287487624357c19b22d2))

Anything else?

No response

[makai410]

This issue is not as simple as "missing path". There is some bugs on trimming the def path.

Consider the examples below:

Example 1

pub mod cat {
    pub mod frog {
        pub enum Meow {
            Foo,
        }
    }
}
fn dog() {
    enum Meow {
        Foo,
    }
}
fn main() {
    let v = cat::frog::Meow::Foo;
    match v {
    }
}

with its output:

error[E0004]: non-exhaustive patterns: `frog::Meow::Foo` not covered
  --> src/main.rs:15:11
   |
15 |     match v {
   |           ^ pattern `frog::Meow::Foo` not covered
   |
note: `frog::Meow` defined here
  --> src/main.rs:3:18
   |
3  |         pub enum Meow {
   |                  ^^^^
4  |             Foo,
   |             --- not covered
   = note: the matched value is of type `frog::Meow`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
   |
16 |     match v {
17 ~         frog::Meow::Foo => todo!(),
18 ~     }
   |

For more information about this error, try `rustc --explain E0004`.
error: could not compile `playground` (bin "playground") due to 1 previous error

---

Example 2

pub mod cat {
    pub mod cat {
        pub enum Meow {
            Foo,
        }
    }
}
fn dog() {
    enum Meow {
        Foo,
    }
}
fn main() {
    let v = cat::cat::Meow::Foo;
    match v {
    }
}

with its output:

error[E0004]: non-exhaustive patterns: `cat::cat::Meow::Foo` not covered
  --> src/main.rs:15:11
   |
15 |     match v {
   |           ^ pattern `cat::cat::Meow::Foo` not covered
   |
note: `cat::cat::Meow` defined here
  --> src/main.rs:3:18
   |
3  |         pub enum Meow {
   |                  ^^^^
4  |             Foo,
   |             --- not covered
   = note: the matched value is of type `cat::cat::Meow`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
   |
16 |     match v {
17 ~         cat::cat::Meow::Foo => todo!(),
18 ~     }
   |

For more information about this error, try `rustc --explain E0004`.
error: could not compile `playground` (bin "playground") due to 1 previous error

it seems to emit a right code suggestion, but if we remove the function dog:

Example 3

pub mod cat {
    pub mod cat {
        pub enum Meow {
            Foo,
        }
    }
}
fn main() {
    let v = cat::cat::Meow::Foo;
    match v {
    }
}

with its output:

error[E0004]: non-exhaustive patterns: `Meow::Foo` not covered
  --> src/main.rs:10:11
   |
10 |     match v {
   |           ^ pattern `Meow::Foo` not covered
   |
note: `Meow` defined here
  --> src/main.rs:3:18
   |
3  |         pub enum Meow {
   |                  ^^^^
4  |             Foo,
   |             --- not covered
   = note: the matched value is of type `Meow`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
   |
11 |     match v {
12 ~         Meow::Foo => todo!(),
13 ~     }
   |

For more information about this error, try `rustc --explain E0004`.
error: could not compile `playground` (bin "playground") due to 1 previous error

[makai410]

This issue corresponds to #137682 , actually reporting the same problem.

[moxian]

Seemingly bisects to #73996 ; the cat:: prefix used to be present in the diagnostics in rustc 1.47.0 and earlier.

#137682 is technically a different problem, since the incorrect function name suggestion has been present all the way since rust 1.10.0

[makai410]

Seemingly bisects to #73996 ; the cat:: prefix used to be present in the diagnostics in rustc 1.47.0 and earlier.

#137682 is technically a different problem, since the incorrect function name suggestion has been present all the way since rust 1.10.0

Thanks for catching this! I will close this issue since it's by design.