phashmap_inst_coherence.lean:11:0: error: type mismatch at application
  PersistentHashMap.find m
term
  m
has type
  @PersistentHashMap Nat Nat Nat.Hashable (@beqOfEq Nat Nat.DecidableEq)
but is expected to have type
  @PersistentHashMap Nat Nat natDiffHash (@beqOfEq Nat Nat.DecidableEq)