Pattern matching on Type in Idris

问题

Probably it's elementary but I don't understand why the following function answers 1 for fnc Nat and also, for fnc Integer, which is not even included as a pattern.

fnc : Type -> Integer
fnc Bool = 1
fnc Nat = 2

回答1:

You can't pattern match on type and you shouldn't. When I compile your code I receive next error:

warning - Unreachable case: fnc Nat

This was already discussed earlier:

1. Old discussion.
2. Some similar question.
3. Some similar issue on GitHub.

UPDATE:

Finally found more relevant question with answer:

Why is typecase a bad thing?

来源：https://stackoverflow.com/questions/45439486/pattern-matching-on-type-in-idris