We didn't handle absurd clauses without absurd patterns

data False
open data Truth | rua
def f Truth : False
| rua
def inconsistency : False => f rua

[ice1000]

Is there an pass after this to check again if None expr is actually not type-checked?

I think you can even do that before type checking. You may also add a boolean variable for the presence of absurd patterns and report error if the boolean is false and the body is None.

[ice1000]

Seems that match expressions do not have coverage checks. /cc @wsx-ucb