I'm not sure if this is a bug or not.

enum Never {} fn works(x: &mut Result<Never, String>) { match x { &mut Ok(ref mut y) => match x { &mut Err(ref mut z) => { let _y = y; let _z = z; } _ => {} }, _ => {} }; } fn fails(x: &mut Result<String, String>) { match x { &mut Ok(ref mut y) => match x { &mut Err(ref mut z) => { let _y = y; let _z = z; } _ => {} }, _ => {} }; }

I expected either both functions to compile or both functions to fail to compile. Instead, only the fails function gives the following error:

error[E0503]: cannot use `*x` because it was mutably borrowed --> src/lib.rs:18:37 | 18 | &mut Ok(ref mut y) => match x { | --------- ^ use of borrowed `x.0` | | | `x.0` is borrowed here 19 | &mut Err(ref mut z) => { 20 | let _y = y; | - borrow later used here For more information about this error, try `rustc --explain E0503`. 

In my understanding, whether &mut Never is uninhabited is undecided. Therefore, since I'm only creating references to Never (as opposed to actually creating Never values) I would think that I wouldn't get any special casing for uninhabited types. Thus, the current behavior seems wrong to me.

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Reproducible on the playground with version 1.92.0-nightly (2025-09-14 52618eb338609df44978)