Dodo doc > Types > Syntax
Unlike variable names, type names always start with an upper case letter. They can contain upper or lower case letters, digits and underscore. There is no extended syntax for type names.
Rationale: The initial upper case letter helps distinguish a type name from a variable name, a function name from a constructor name. Extended characters are not allowed because keeping this distinction would become unwieldy if they were.
^ 4. Types