https://www.haskell.org/onlinereport/lexemes.html#ids

In the above link, there is the following syntax:
```haskell
varid	->	(small {small | large | digit | ' })<reservedid>
conid	->	large {small | large | digit | ' }
reservedid	->	case | class | data | default | deriving | do | else
|	if | import | in | infix | infixl | infixr | instance
|	let | module | newtype | of | then | type | where | _

```