*** Process tests/Duplicate.newt
module Duplicate
ERROR at tests/Duplicate.newt:5:1--5:5: Duplicate.Left is already defined at tests/Duplicate.newt:5:1--5:5
  -- duplicate name should fail
  -- FIXME FC is wrong here
  data Either : U -> U -> U where
  ^^^^

ERROR at tests/Duplicate.newt:1:1--1:2: Compile failed