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

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

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