While checking REPL.f:
  Error: the pattern
    left(x)
  is supposed to have type
    List(ℤ),
  but instead it has a sum type.
  https://disco-lang.readthedocs.io/en/latest/reference/pattern-type.html
While checking REPL.g:
  Error: the pattern
    (x1, y)
  is supposed to have type
    ℕ,
  but instead it has a product type.
  https://disco-lang.readthedocs.io/en/latest/reference/pattern-type.html
While checking REPL.h:
  Error: the shape of two types does not match.
  https://disco-lang.readthedocs.io/en/latest/reference/shape-mismatch.html