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

State before:
x y : Pos
⊢ x + 1 + y = x + y + 1
Tactic:
by_toNat
State after:
x y : Pos
⊢ x.toNat + 1 + y.toNat = x.toNat + y.toNat + 1

State before:
x y : Pos
⊢ x.toNat + 1 + y.toNat = x.toNat + y.toNat + 1
Tactic:
exact Nat.succ_add ..
State after:
no goals