Function layout 

pub(super) fn layout<'a, F, VariantIdx, FieldIdx, LocalIdx>(
    calc: &LayoutCalculator<impl HasDataLayout>,
    local_layouts: &IndexSlice<LocalIdx, F>,
    prefix_layouts: IndexVec<FieldIdx, F>,
    variant_fields: &IndexSlice<VariantIdx, IndexVec<FieldIdx, LocalIdx>>,
    storage_conflicts: &BitMatrix<LocalIdx, LocalIdx>,
    tag_to_layout: impl Fn(Scalar) -> F,
) -> Result<LayoutData<FieldIdx, VariantIdx>, LayoutCalculatorError<F>>
where
    F: Deref<Target = &'a LayoutData<FieldIdx, VariantIdx>> + Debug + Copy,
    VariantIdx: Idx,
    FieldIdx: Idx,
    LocalIdx: Idx,

Compute the full coroutine layout.