| An enum with the representation hint `repr(transparent)` had zero or more than | |
| one variants. | |
| Erroneous code example: | |
| ```compile_fail,E0731 | |
| #[repr(transparent)] | |
| enum Status { // error: transparent enum needs exactly one variant, but has 2 | |
| Errno(u32), | |
| Ok, | |
| } | |
| ``` | |
| Because transparent enums are represented exactly like one of their variants at | |
| run time, said variant must be uniquely determined. If there is no variant, or | |
| if there are multiple variants, it is not clear how the enum should be | |
| represented. |