Set: pp::colors
  Set: pp::unicode
Importing file 'simple.lean'
  Assumed: x
  Assumed: y
Module 'simple.lean' has already been imported
Importing file 'simple.lean'
  Assumed: x
  Assumed: y
Module 'simple.lean' has already been imported
x + y : ℤ
  Assumed: z
z : ℤ
Error (line: 14, pos: 6) unknown identifier 'z'