T7294.hs:23:1: warning:
    Pattern match(es) are redundant
    In an equation for ‘nth’: nth Nil _ = ...

T7294.hs:25:5: Warning:
    Couldn't match type ‘'True’ with ‘'False’
    Inaccessible code in
      a pattern with constructor: Nil :: forall a. Vec a 'Zero,
      in an equation for ‘nth’
    In the pattern: Nil
    In an equation for ‘nth’: nth Nil _ = undefined