|  | // from rfc2005 test suite | 
|  |  | 
|  |  | 
|  |  | 
|  | // Verify the binding mode shifts - only when no `&` are auto-dereferenced is the | 
|  | // final default binding mode mutable. | 
|  |  | 
|  | fn main() { | 
|  | let Some(n) = &&Some(5i32) else { return }; | 
|  | *n += 1; //~ ERROR cannot assign to `*n`, which is behind a `&` reference | 
|  | let _ = n; | 
|  |  | 
|  | let Some(n) = &mut &Some(5i32) else { return }; | 
|  | *n += 1; //~ ERROR cannot assign to `*n`, which is behind a `&` reference | 
|  | let _ = n; | 
|  |  | 
|  | let Some(n) = &&mut Some(5i32) else { return }; | 
|  | *n += 1; //~ ERROR cannot assign to `*n`, which is behind a `&` reference | 
|  | let _ = n; | 
|  | } |