pub use derive_refineable::Refineable; /// A trait for types that can be refined with partial updates.////// The `Refineable` trait enables hierarchical configuration patterns where a base configuration/// can be selectively overridden by refinements. This is particularly useful for styling and/// settings, and theme hierarchies.////// # Derive Macro////// The `#[derive(Refineable)]` macro automatically generates a companion refinement type and/// implements this trait. For a struct `Style`, it creates `StyleRefinement` where each field is/// wrapped appropriately:////// - **Refineable fields** (marked with `#[refineable]`): Become the corresponding refinement type///   (e.g., `Bar` becomes `BarRefinement`)/// - **Optional fields** (`Option<T>`): Remain as `Option<T>`/// - **Regular fields**: Become `Option<T>`////// ## Example////// ```rust/// #[derive(Refineable, Clone, Default)]/// struct Example {///     color: String,///     font_size: Option<u32>,///     #[refineable]///     margin: Margin,/// }////// #[derive(Refineable, Clone, Default)]/// struct Margin {///     top: u32,///     left: u32,/// }///////// fn example() {///     let mut example = Example::default();///     let refinement = ExampleRefinement {///         color: Some("red".to_string()),///         font_size: None,///         margin: MarginRefinement {///             top: Some(10),///             left: None,///         },///     };//////     base_style.refine(&refinement);/// }/// ```////// This generates `ExampleRefinement` with:/// - `color: Option<String>`/// - `font_size: Option<u32>` (unchanged)/// - `margin: MarginRefinement`////// ## Attributes////// The derive macro supports these attributes on the struct:/// - `#[refineable(Debug)]`: Implements `Debug` for the refinement type/// - `#[refineable(Serialize)]`: Derives `Serialize` which skips serializing `None`/// - `#[refineable(OtherTrait)]`: Derives additional traits on the refinement type////// Fields can be marked with:/// - `#[refineable]`: Field is itself refineable (uses nested refinement type)pub trait Refineable: Clone {    type Refinement: Refineable<Refinement = Self::Refinement> + IsEmpty + Default;     /// Applies the given refinement to this instance, modifying it in place.    ///    /// Only non-empty values in the refinement are applied.    ///    /// * For refineable fields, this recursively calls `refine`.    /// * For other fields, the value is replaced if present in the refinement.    fn refine(&mut self, refinement: &Self::Refinement);     /// Returns a new instance with the refinement applied, equivalent to cloning `self` and calling    /// `refine` on it.    fn refined(self, refinement: Self::Refinement) -> Self;     /// Creates an instance from a cascade by merging all refinements atop the default value.    fn from_cascade(cascade: &Cascade<Self>) -> Self    where        Self: Default + Sized,    {        Self::default().refined(cascade.merged())    }     /// Returns `true` if this instance would contain all values from the refinement.    ///    /// For refineable fields, this recursively checks `is_superset_of`. For other fields, this    /// checks if the refinement's `Some` values match this instance's values.    fn is_superset_of(&self, refinement: &Self::Refinement) -> bool;     /// Returns a refinement that represents the difference between this instance and the given    /// refinement.    ///    /// For refineable fields, this recursively calls `subtract`. For other fields, the field is    /// `None` if the field's value is equal to the refinement.    fn subtract(&self, refinement: &Self::Refinement) -> Self::Refinement;} pub trait IsEmpty {    /// Returns `true` if applying this refinement would have no effect.    fn is_empty(&self) -> bool;} /// A cascade of refinements that can be merged in priority order.////// A cascade maintains a sequence of optional refinements where later entries/// take precedence over earlier ones. The first slot (index 0) is always the/// base refinement and is guaranteed to be present.////// This is useful for implementing configuration hierarchies like CSS cascading,/// where styles from different sources (user agent, user, author) are combined/// with specific precedence rules.pub struct Cascade<S: Refineable>(Vec<Option<S::Refinement>>); impl<S: Refineable + Default> Default for Cascade<S> {    fn default() -> Self {        Self(vec![Some(Default::default())])    }} /// A handle to a specific slot in a cascade.////// Slots are used to identify specific positions in the cascade where/// refinements can be set or updated.#[derive(Copy, Clone)]pub struct CascadeSlot(usize); impl<S: Refineable + Default> Cascade<S> {    /// Reserves a new slot in the cascade and returns a handle to it.    ///    /// The new slot is initially empty (`None`) and can be populated later    /// using `set()`.    pub fn reserve(&mut self) -> CascadeSlot {        self.0.push(None);        CascadeSlot(self.0.len() - 1)    }     /// Returns a mutable reference to the base refinement (slot 0).    ///    /// The base refinement is always present and serves as the foundation    /// for the cascade.    pub fn base(&mut self) -> &mut S::Refinement {        self.0[0].as_mut().unwrap()    }     /// Sets the refinement for a specific slot in the cascade.    ///    /// Setting a slot to `None` effectively removes it from consideration    /// during merging.    pub fn set(&mut self, slot: CascadeSlot, refinement: Option<S::Refinement>) {        self.0[slot.0] = refinement    }     /// Merges all refinements in the cascade into a single refinement.    ///    /// Refinements are applied in order, with later slots taking precedence.    /// Empty slots (`None`) are skipped during merging.    pub fn merged(&self) -> S::Refinement {        let mut merged = self.0[0].clone().unwrap();        for refinement in self.0.iter().skip(1).flatten() {            merged.refine(refinement);        }        merged    }}