| A cast to `char` was attempted on a type other than `u8`. |
| |
| Erroneous code example: |
| |
| ```compile_fail,E0604 |
| 0u32 as char; // error: only `u8` can be cast as `char`, not `u32` |
| ``` |
| |
| `char` is a Unicode Scalar Value, an integer value from 0 to 0xD7FF and |
| 0xE000 to 0x10FFFF. (The gap is for surrogate pairs.) Only `u8` always fits in |
| those ranges so only `u8` may be cast to `char`. |
| |
| To allow larger values, use `char::from_u32`, which checks the value is valid. |
| |
| ``` |
| assert_eq!(86u8 as char, 'V'); // ok! |
| assert_eq!(char::from_u32(0x3B1), Some('α')); // ok! |
| assert_eq!(char::from_u32(0xD800), None); // not a USV. |
| ``` |
| |
| For more information about casts, take a look at the Type cast section in |
| [The Reference Book][1]. |
| |
| [1]: https://doc.rust-lang.org/reference/expressions/operator-expr.html#type-cast-expressions |
