Theorem: Pos.add_comm (Extra/Pos/Lemmas.lean)

State before:
x y : Pos
⊢ x + y = y + x
Tactic:
by_toNat
State after:
x y : Pos
⊢ x.toNat + y.toNat = y.toNat + x.toNat

State before:
x y : Pos
⊢ x.toNat + y.toNat = y.toNat + x.toNat
Tactic:
exact Nat.add_comm ..
State after:
no goals