nested_errors.lean:7:13: error: intro tactic failed, Pi/let expression expected state: a b c : ℕ, a_1 : a = b, a_2 : c = b ⊢ a = c nested_errors.lean:7:2: error: failed state: a b c : ℕ, a_1 : a = b, a_2 : c = b ⊢ a = c nested_errors.lean:8:0: error: failed state: a b c : ℕ, a_1 : a = b, a_2 : c = b ⊢ a = c