Theorem: back?_isSome (Algorithm/Data/Classes/ToList.lean)

State before:
C : Type u_1
α : Type u_2
inst✝¹ : ToList C α
inst✝ : Back C α
c : C
h : ¬isEmpty c = true
⊢ (back? c).isSome = true
Tactic:
rwa [back?_def, List.getLast?_isSome, ← List.not_isEmpty_iff_ne_nil, isEmpty_toList]
State after:
no goals