import Lean open Lean Meta #eval id (α := MetaM Unit) do modifyEnv fun env => env.addExtraName `auxDecl1 return () def foo := 42 local infix:50 " ≺ " => LE.le #check 1 ≺ 2 local macro "my_refl" : tactic => `(tactic| rfl) def f (x y : Nat) (_h : x = y := by my_refl) := x theorem simple : 10 = 10 := by decide