copse 0.4.0

Direct ports of the standard library's BTreeMap, BTreeSet and BinaryHeap collections, but that sort according to a specified total order rather than the `Ord` trait
Documentation 
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/// Zero-Sized Type (ZST) for internal `BTreeSet` values.
/// Used instead of `()` to differentiate between:
/// * `BTreeMap<T, ()>` (possible user-defined map)
/// * `BTreeMap<T, SetValZST>` (internal set representation)
#[derive(Debug, Eq, PartialEq, Ord, PartialOrd, Hash, Clone, Default)]
pub struct SetValZST;

/// A trait to differentiate between `BTreeMap` and `BTreeSet` values.
/// Returns `true` only for type `SetValZST`, `false` for all other types (blanket implementation).
/// `TypeId` requires a `'static` lifetime, use of this trait avoids that restriction.
///
/// [`TypeId`]: std::any::TypeId
pub trait IsSetVal {
    fn is_set_val() -> bool;
}

// Blanket implementation
#[cfg(feature = "specialization")]
impl<V> IsSetVal for V {
    default fn is_set_val() -> bool {
        false
    }
}

// Specialization
impl IsSetVal for SetValZST {
    fn is_set_val() -> bool {
        true
    }
}