423.lean:3:35-3:40: error: Application type mismatch: The argument
  a
has type
  T
of sort `Sort u` but is expected to have type
  Nat
of sort `Type` in the application
  HAdd.hAdd a
423.lean:5:37-5:38: error: Application type mismatch: The argument
  T
has type
  Sort u
of sort `Type u` but is expected to have type
  Type ?u
of sort `Type (?u + 1)` in the application
  Add T
423.lean:5:47-5:48: error: Application type mismatch: The argument
  T
has type
  Sort u
of sort `Type u` but is expected to have type
  Type ?u
of sort `Type (?u + 1)` in the application
  OfNat T
423.lean:5:55-5:60: error: Application type mismatch: The argument
  a
has type
  T
of sort `Sort u` but is expected to have type
  Nat
of sort `Type` in the application
  HAdd.hAdd a