⦃h, L⦄ ⊢ V •[g, l + 1] W → L ⊢ W ➡* W0 →
⦃h, L⦄ ⊢ T •➡*[g] ⓛ{a}W0.U → snv h g L (ⓐV.T)
| snv_cast: ∀L,W,T,U,l. snv h g L W → snv h g L T →
⦃h, L⦄ ⊢ V •[g, l + 1] W → L ⊢ W ➡* W0 →
⦃h, L⦄ ⊢ T •➡*[g] ⓛ{a}W0.U → snv h g L (ⓐV.T)
| snv_cast: ∀L,W,T,U,l. snv h g L W → snv h g L T →