lean2/tests/lean/run/tactic17.lean

import standard
using tactic

variable A : Type.{1}
variable f : A → A → A

theorem tst {a b c : A} (H1 : a = b) (H2 : b = c) : f a b = f b c
:= by apply (@congr A A (f a) (f b));
      apply (congr_arg f);
      !assumption