Attribute Macro array_slots 

#[array_slots]

Generate slot index constants, a borrowed view struct, and a typed ext trait from a slot struct definition.

Fields must be ArrayRef (required slot) or Option<ArrayRef> (optional slot). Field declaration order determines slot indices.

Example

#[array_slots(Patched)]
pub struct PatchedSlots {
    pub inner: ArrayRef,
    pub lane_offsets: ArrayRef,
    pub patch_indices: ArrayRef,
    pub patch_values: ArrayRef,
}

Generated output

Given the above, the macro generates:

// --- The original struct is preserved as-is ---
pub struct PatchedSlots { ... }

// --- Slot index constants and conversion methods on the struct ---
impl PatchedSlots {
    pub const INNER: usize = 0;
    pub const LANE_OFFSETS: usize = 1;
    pub const PATCH_INDICES: usize = 2;
    pub const PATCH_VALUES: usize = 3;
    pub const COUNT: usize = 4;
    pub const NAMES: [&'static str; 4] = ["inner", "lane_offsets", "patch_indices", "patch_values"];

    /// Take ownership of slots from a `Vec<Option<ArrayRef>>`.
    pub fn from_slots(slots: Vec<Option<ArrayRef>>) -> Self { ... }

    /// Convert back into storage order.
    pub fn into_slots(self) -> Vec<Option<ArrayRef>> { ... }
}

// --- Borrowed view with &ArrayRef / Option<&ArrayRef> fields ---
pub struct PatchedSlotsView<'a> {
    pub inner: &'a ArrayRef,
    pub lane_offsets: &'a ArrayRef,
    pub patch_indices: &'a ArrayRef,
    pub patch_values: &'a ArrayRef,
}

impl<'a> PatchedSlotsView<'a> {
    pub fn from_slots(slots: &'a [Option<ArrayRef>]) -> Self { ... }
    pub fn to_owned(&self) -> PatchedSlots { ... }
}

// --- Ext trait with per-field accessors + slots_view() ---
pub trait PatchedArraySlotsExt: TypedArrayRef<Patched> {
    fn inner(&self) -> &ArrayRef { ... }         // indexes slots directly
    fn lane_offsets(&self) -> &ArrayRef { ... }
    fn patch_indices(&self) -> &ArrayRef { ... }
    fn patch_values(&self) -> &ArrayRef { ... }
    fn slots_view(&self) -> PatchedSlotsView<'_> { ... }
}

impl<T: TypedArrayRef<Patched>> PatchedArraySlotsExt for T {}

Required vs optional slots

• ArrayRef — the slot must be present. from_slots() panics if None. The ext trait accessor returns &ArrayRef. The view field is &'a ArrayRef.

• Option<ArrayRef> — the slot may be absent. from_slots() preserves None. The ext trait accessor returns Option<&ArrayRef>. The view field is Option<&'a ArrayRef>.

The underlying storage is always Vec<Option<ArrayRef>> — the field type only controls whether the macro inserts a .vortex_expect() unwrap or not.