elab12.lean:1:30: error: type expected at
  0
elab12.lean:4:42: error: function expected at
  rfl
Additional information:
elab12.lean:4:42: context: switched to simple application elaboration procedure because failed to use expected type to elaborate it, error message
  too many arguments
elab12.lean:7:44: error: failed to synthesize type class instance for
a : ℕ
⊢ has_add (a = a)
elab12.lean:11:2: error: function expected at
  H
λ (a : ℕ), have H : a = a, from rfl, H : ∀ (a : ℕ), a = a