Generics constrain with numbers

[archnim]

This is something I don't understand : The implementation of SomeOrdinal in 
/lib/system/basic_types.nim, on line 32 is the following:
    
    
    SomeOrdinal* = 
int|int8|int16|int32|int64|bool|enum|uint|uint8|uint16|uint32|uint64
    
    
    Run

Isn't it better (shorter) to write : `SomeOrdinal* = SomeInteger | bool | enum` 
?