1/1: Building loopy (loopy.idr)
Error: While processing right hand side of eatBinary. While processing right hand side of eatBinary,firstDigit. Patterns for eatBinary,firstDigit,f require matching on different types.

loopy:24:5--24:18
 20 |   firstDigit : List Char -> i
 21 |   firstDigit [] = 0
 22 |   firstDigit (d :: ds) = let
 23 |     f : Maybe i -> i
 24 |     f Nothing = 0
          ^^^^^^^^^^^^^