1/1: Building unboundimps (unboundimps.idr)
Error: While processing type of len'. Undefined name xs. 

unboundimps:18:11--18:13
 14 | -- xs and its indices
 15 | len : forall xs . Env xs -> Nat
 16 | 
 17 | -- neither of these are fine
 18 | len': Env xs -> Nat
                ^^

Error: While processing type of append'. Undefined name n. 

unboundimps:19:16--19:17
 15 | len : forall xs . Env xs -> Nat
 16 | 
 17 | -- neither of these are fine
 18 | len': Env xs -> Nat
 19 | append' : Vect n a -> Vect m a -> Vect (n + m) a
                     ^