Productivity.err

Termination checking failed for the following functions:
  expr, term, factor
Problematic calls:
  term
    (at Productivity.agda:36,14-18)
  factor
    (at Productivity.agda:37,14-20)
  .Productivity.♯-9
    (at Productivity.agda:38,25-26)
  .Productivity.♯-10
    (at Productivity.agda:38,28-29)
  .Productivity.♯-12
    (at Productivity.agda:38,45-46)
  expr
    (at Productivity.agda:38,47-51)