Function eff_sliceindex_get_unchecked 

fn eff_sliceindex_get_unchecked(ctx: &EffCtx<'_, '_>) -> Vec<CallEffect>

SliceIndex::get_unchecked(self, slice) / get_unchecked_mut: returns an element pointer at slice + self (receiver is the index, slice pointer is argument 1). Element-strided add off argument 1, inheriting non-nullness from the slice.