Set: pp::colors
  Set: pp::unicode
  Assumed: N
  Assumed: a
kernel_ex1.lean:3:14 error: type expected, got
    a
kernel_ex1.lean:4:6 error: function expected at
    a a
  Assumed: f
kernel_ex1.lean:6:6 error: type mismatch at application
    f (λ x : N, x)
Function type:
    N → N
Argument type:
    (λ x : N, x) : N → N