|  | error[E0605]: non-primitive cast: `NonNullary` as `isize` | 
|  | --> $DIR/cast-enum-to-primitive-error.rs:24:15 | 
|  | | | 
|  | LL |     let val = v as isize; | 
|  | |               ^^^^^^^^^^ an `as` expression can be used to convert enum types to numeric types only if the enum type is unit-only or field-less | 
|  | | | 
|  | = note: see https://doc.rust-lang.org/reference/items/enumerations.html#casting for more information | 
|  | help: consider using the `From` trait instead | 
|  | | | 
|  | LL -     let val = v as isize; | 
|  | LL +     let val = isize::from(v); | 
|  | | | 
|  |  | 
|  | error: aborting due to 1 previous error | 
|  |  | 
|  | For more information about this error, try `rustc --explain E0605`. |