Suggest &* when appropriate

[estebank]

Code

use std::sync::Arc;
fn main() {
    let mut x = Arc::new(Some(1));
    match x {
        Some(_) => {}
        None => {}
    }
}

Current output

error[E0308]: mismatched types
 --> src/main.rs:5:9
  |
4 |     match x {
  |           - this expression has type `Arc<Option<{integer}>>`
5 |         Some(_) => {}
  |         ^^^^^^^ expected `Arc<Option<{integer}>>`, found `Option<_>`
  |
  = note: expected struct `Arc<Option<{integer}>>`
               found enum `Option<_>`

error[E0308]: mismatched types
 --> src/main.rs:6:9
  |
4 |     match x {
  |           - this expression has type `Arc<Option<{integer}>>`
5 |         Some(_) => {}
6 |         None => {}
  |         ^^^^ expected `Arc<Option<{integer}>>`, found `Option<_>`
  |
  = note: expected struct `Arc<Option<{integer}>>`
               found enum `Option<_>`

Desired output

error[E0308]: mismatched types
 --> src/main.rs:5:9
  |
4 |     match x {
  |           - this expression has type `Arc<Option<{integer}>>`
5 |         Some(_) => {}
  |         ^^^^^^^ expected `Arc<Option<{integer}>>`, found `Option<_>`
  |
  = note: expected struct `Arc<Option<{integer}>>`
               found enum `Option<_>`
help: you can dereference the `Arc<Option<_>>` to `Option<_>` to make the types match
  |
4 |     match &*x {
  |          ++

Rationale and extra context

https://users.rust-lang.org/t/type-errors-are-a-part-of-library-api-surface-and-a-fundamental-shortcoming-in-rust/120859

Other cases

Rust Version

1.82

Anything else?

No response

[uellenberg]

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