apply Iff.intro
B : State → Prop
s t : State
⊢ (Stmt.assert B, s) ⟹ t ↔ t = s ∧ B s
case mp
B : State → Prop
s t : State
⊢ (Stmt.assert B, s) ⟹ t → t = s ∧ B s

case mpr
B : State → Prop
s t : State
⊢ t = s ∧ B s → (Stmt.assert B, s) ⟹ t