-- Hindley-Milner type inference is exponential -- Demo.

test =
  let f1 x = (x, x)
      f2 x = f1 (f1 x)
      f3 x = f2 (f2 x)
      f4 x = f3 (f3 x)
      f5 x = f4 (f4 x)
      f6 x = f5 (f5 x)    -- This is the killer!
  in  f5 id