bevy_shuffle_bag 0.1.1

#![warn(missing_docs)]
#![doc = include_str!("../readme.md")]

#[cfg(feature = "bevy_assets")]
use bevy::asset::VisitAssetDependencies;
use bevy::prelude::*;
use rand::{Rng, seq::SliceRandom as _};
use std::{
    fmt::{Debug, Formatter},
    hash::{Hash, Hasher},
};

/// A bag full of items that can endlessly be picked in a random order.
///
/// The bag will be emptied in *drafts*, where each draft contains all the items in the bag, but in a random order.
/// This means that if you have e.g. a bag with 3 soundtracks, all of them will play once in a random order, and then the bag will be refilled with the same soundtracks in a random order.
/// If the bag contains no duplicates, items are always picked such that the same item is never picked twice in a row.
///
/// No more playing the same sound effect or dialogue twice in a row!
#[derive(Component, Resource)]
#[non_exhaustive]
pub struct ShuffleBag<T> {
    /// The full collection of items that could be in the bag at the same time.
    pub full_collection: Vec<T>,
    /// The indices of the current draft of items that can be picked from the bag.
    pub current_draft: Vec<usize>,
    /// The last item that was picked from the bag. If the bag was just created, this will be `None`.
    pub last_pick: Option<usize>,
}

impl<T> ShuffleBag<T> {
    /// Create a new shuffle bag from an iterator. Returns `None` if the iterator is empty.
    ///
    /// # Example
    /// ```
    /// # use bevy::prelude::*;
    /// # use std::collections::HashSet;
    /// # use bevy_shuffle_bag::ShuffleBag;
    /// let mut rng = rand::thread_rng();
    /// let mut possible_loot = HashSet::new();
    /// possible_loot.insert("gold");
    /// possible_loot.insert("armor");
    /// possible_loot.insert("sword");
    /// let treasure_chest = ShuffleBag::try_from_iter(possible_loot, &mut rng).unwrap();
    /// ```
    pub fn try_from_iter(iter: impl IntoIterator<Item = T>, rng: &mut impl Rng) -> Option<Self> {
        let full_collection: Vec<_> = iter.into_iter().collect();
        Self::try_new(full_collection, rng)
    }

    /// Create a new shuffle bag from something that can be converted into a vector. Returns `None` if the vector is empty.
    ///
    /// # Example
    /// ```
    /// # use bevy::prelude::*;
    /// # use bevy_shuffle_bag::ShuffleBag;
    /// let mut rng = rand::thread_rng();
    /// let treasure_chest = ShuffleBag::try_new(["gold", "armor", "sword"], &mut rng).unwrap();
    /// ```
    pub fn try_new(full_collection: impl Into<Vec<T>>, rng: &mut impl Rng) -> Option<Self> {
        let full_collection = full_collection.into();
        if full_collection.is_empty() {
            return None;
        }

        let mut bag = Self {
            full_collection,
            current_draft: vec![],
            last_pick: None,
        };

        bag.shuffle_new_draft(rng);
        Some(bag)
    }

    /// Shuffle a new draft of the bag. This is automatically called when the bag is empty or when the bag is first created.
    ///
    /// "Draft" here means the collection of items that can be picked from the bag.
    /// After this call, the draft will contain all the items in the bag, but in a random order.
    /// The draft is constructed such that the next item to be picked by [`ShuffleBag::pick`] is not the same as the last item that was picked.
    ///
    /// # Example
    /// ```
    /// # use bevy::prelude::*;
    /// # use bevy_shuffle_bag::ShuffleBag;
    /// let mut rng = rand::thread_rng();
    /// let mut treasure_chest = ShuffleBag::try_new(["gold", "armor", "sword"], &mut rng).unwrap();
    /// let loot = treasure_chest.pick(&mut rng);
    ///
    /// // The player just used a joker to get a new item! Let's reshuffle the bag. Doing so will
    /// // still ensure that the same item is never picked twice in a row.
    /// treasure_chest.shuffle_new_draft(&mut rng);
    /// let new_loot = treasure_chest.pick(&mut rng);
    /// ```
    pub fn shuffle_new_draft(&mut self, rng: &mut impl Rng) {
        self.current_draft = (0..self.full_collection.len()).collect();
        self.current_draft.shuffle(rng);

        if self.current_draft.len() <= 1 {
            return;
        }

        let Some(last_pick) = &self.last_pick else {
            return;
        };

        if self.current_draft.last() != Some(last_pick) {
            return;
        }

        // Looks like we picked the same item twice in a row, so let's shuffle it into the middle of the draft.
        let max_index = self.current_draft.len() - 2;
        let index = rng.gen_range(0..=max_index);
        // Swap the this item with the last item in the draft.
        let new_next_pick = self.current_draft.swap_remove(index);
        self.current_draft.push(new_next_pick);
    }

    /// Shuffle a new draft of the bag and forget the last item that was picked.
    ///
    /// # Example
    /// ```
    /// # use bevy::prelude::*;
    /// # use bevy_shuffle_bag::ShuffleBag;
    /// let mut rng = rand::thread_rng();
    /// let mut treasure_chest = ShuffleBag::try_new(["gold", "armor", "sword"], &mut rng).unwrap();
    /// let loot = treasure_chest.pick(&mut rng);
    ///
    /// // The player just reloaded from a save, so let's reset the bag.
    /// treasure_chest.reset(&mut rng);
    /// let new_loot = treasure_chest.pick(&mut rng);
    /// ```
    pub fn reset(&mut self, rng: &mut impl Rng) {
        self.current_draft = vec![];
        self.last_pick = None;
        self.shuffle_new_draft(rng);
    }

    /// Pick an item from the bag. If the bag is empty, this will automatically shuffle a new draft.
    /// If there are no duplicates in the bag, this will never pick the same item twice in a row.
    ///
    /// # Example
    /// ```
    /// # use bevy::prelude::*;
    /// # use bevy_shuffle_bag::ShuffleBag;
    /// let mut rng = rand::thread_rng();
    /// let mut treasure_chest = ShuffleBag::try_new(["gold", "armor", "sword"], &mut rng).unwrap();
    /// let loot = treasure_chest.pick(&mut rng);
    /// ```
    pub fn pick(&mut self, rng: &mut impl Rng) -> &T {
        let pick = self.current_draft.pop().unwrap();
        self.last_pick = Some(pick);

        if self.current_draft.is_empty() {
            self.shuffle_new_draft(rng);
        }

        &self.full_collection[pick]
    }

    /// Peek at the next item that would be picked from the bag.
    ///
    /// # Example
    /// ```
    /// # use bevy::prelude::*;
    /// # use bevy_shuffle_bag::ShuffleBag;
    /// let mut rng = rand::thread_rng();
    /// let mut shop = ShuffleBag::try_new(["potion", "shield", "bow"], &mut rng).unwrap();
    ///
    /// // The player is browsing the shop. The shopkeeper randomly picks an item that is available for purchase.
    /// let available_purchase = shop.peek().clone();
    ///
    /// // The player likes what they see, so they buy it!
    /// let purchased_item = shop.pick(&mut rng).clone();
    ///
    /// assert_eq!(purchased_item, available_purchase);
    /// ```
    pub fn peek(&self) -> &T {
        &self.full_collection[*self.current_draft.last().unwrap()]
    }
}

impl<T: Debug> Debug for ShuffleBag<T> {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("ShuffleBag")
            .field("full_collection", &self.full_collection)
            .field("current_draft", &self.current_draft)
            .field("last_pick", &self.last_pick)
            .finish()
    }
}

impl<T: Clone> Clone for ShuffleBag<T> {
    fn clone(&self) -> Self {
        Self {
            full_collection: self.full_collection.clone(),
            current_draft: self.current_draft.clone(),
            last_pick: self.last_pick,
        }
    }
}

impl<T: PartialEq> PartialEq for ShuffleBag<T> {
    fn eq(&self, other: &Self) -> bool {
        self.full_collection == other.full_collection
            && self.current_draft == other.current_draft
            && self.last_pick == other.last_pick
    }
}

impl<T: Eq> Eq for ShuffleBag<T> {}

impl<T: Hash + Clone> Hash for ShuffleBag<T> {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.full_collection.hash(state);
        self.current_draft.hash(state);
        self.last_pick.hash(state);
    }
}

impl<T: VisitAssetDependencies> VisitAssetDependencies for ShuffleBag<T> {
    fn visit_dependencies(&self, visit: &mut impl FnMut(bevy::asset::UntypedAssetId)) {
        for item in &self.full_collection {
            item.visit_dependencies(visit);
        }
    }
}

// The following is adapted from the output of `cargo expand`. Run `cargo_expand/expand.sh` to generate the template.
const _: () = {
    #[allow(unused_mut)]
    impl<T: PartialEq + Eq> bevy::reflect::GetTypeRegistration for ShuffleBag<T>
    where
        ShuffleBag<T>: ::core::any::Any + ::core::marker::Send + ::core::marker::Sync,
        Vec<T>: bevy::reflect::FromReflect
            + bevy::reflect::TypePath
            + bevy::reflect::MaybeTyped
            + bevy::reflect::__macro_exports::RegisterForReflection,
    {
        fn get_type_registration() -> bevy::reflect::TypeRegistration {
            let mut registration = bevy::reflect::TypeRegistration::of::<Self>();
            registration.insert::<bevy::reflect::ReflectFromPtr>(
                bevy::reflect::FromType::<Self>::from_type(),
            );
            registration.insert::<bevy::reflect::ReflectFromReflect>(
                bevy::reflect::FromType::<Self>::from_type(),
            );
            registration.insert::<ReflectComponent>(bevy::reflect::FromType::<Self>::from_type());
            registration.insert::<ReflectResource>(bevy::reflect::FromType::<Self>::from_type());
            registration
        }
        #[inline(never)]
        fn register_type_dependencies(registry: &mut bevy::reflect::TypeRegistry) {
            <Vec<T> as bevy::reflect::__macro_exports::RegisterForReflection>::__register(registry);
            <Vec<usize> as bevy::reflect::__macro_exports::RegisterForReflection>::__register(
                registry,
            );
            <Option<usize> as bevy::reflect::__macro_exports::RegisterForReflection>::__register(
                registry,
            );
        }
    }
    impl<T> bevy::reflect::Typed for ShuffleBag<T>
    where
        ShuffleBag<T>: ::core::any::Any + ::core::marker::Send + ::core::marker::Sync,
        Vec<T>: bevy::reflect::FromReflect
            + bevy::reflect::TypePath
            + bevy::reflect::MaybeTyped
            + bevy::reflect::__macro_exports::RegisterForReflection,
    {
        #[inline]
        fn type_info() -> &'static bevy::reflect::TypeInfo {
            static CELL: bevy::reflect::utility::NonGenericTypeInfoCell =
                bevy::reflect::utility::NonGenericTypeInfoCell::new();
            CELL.get_or_set(|| {
                bevy::reflect::TypeInfo::Struct(
                    bevy::reflect::StructInfo::new::<Self>(&[
                        bevy::reflect::NamedField::new::<Vec<T>>("full_collection")
                            .with_custom_attributes(
                                bevy::reflect::attributes::CustomAttributes::default(),
                            ),
                        bevy::reflect::NamedField::new::<Vec<usize>>("current_draft")
                            .with_custom_attributes(
                                bevy::reflect::attributes::CustomAttributes::default(),
                            ),
                        bevy::reflect::NamedField::new::<Option<usize>>("last_pick")
                            .with_custom_attributes(
                                bevy::reflect::attributes::CustomAttributes::default(),
                            ),
                    ])
                    .with_custom_attributes(bevy::reflect::attributes::CustomAttributes::default()),
                )
            })
        }
    }
    impl<T> bevy::reflect::TypePath for ShuffleBag<T>
    where
        ShuffleBag<T>: ::core::any::Any + ::core::marker::Send + ::core::marker::Sync,
    {
        fn type_path() -> &'static str {
            "bevy_shuffle_bag::ShuffleBag"
        }
        fn short_type_path() -> &'static str {
            "ShuffleBag"
        }
        fn type_ident() -> Option<&'static str> {
            ::core::option::Option::Some("ShuffleBag")
        }
        fn crate_name() -> Option<&'static str> {
            ::core::option::Option::Some("bevy_shuffle_bag".split(':').next().unwrap())
        }
        fn module_path() -> Option<&'static str> {
            ::core::option::Option::Some("bevy_shuffle_bag")
        }
    }
    impl<T> bevy::reflect::Reflect for ShuffleBag<T>
    where
        ShuffleBag<T>: ::core::any::Any + ::core::marker::Send + ::core::marker::Sync,
        Vec<T>: bevy::reflect::FromReflect
            + bevy::reflect::TypePath
            + bevy::reflect::MaybeTyped
            + bevy::reflect::__macro_exports::RegisterForReflection,
    {
        #[inline]
        fn into_any(self: ::std::boxed::Box<Self>) -> ::std::boxed::Box<dyn ::core::any::Any> {
            self
        }
        #[inline]
        fn as_any(&self) -> &dyn ::core::any::Any {
            self
        }
        #[inline]
        fn as_any_mut(&mut self) -> &mut dyn ::core::any::Any {
            self
        }
        #[inline]
        fn into_reflect(
            self: ::std::boxed::Box<Self>,
        ) -> ::std::boxed::Box<dyn bevy::reflect::Reflect> {
            self
        }
        #[inline]
        fn as_reflect(&self) -> &dyn bevy::reflect::Reflect {
            self
        }
        #[inline]
        fn as_reflect_mut(&mut self) -> &mut dyn bevy::reflect::Reflect {
            self
        }
        #[inline]
        fn set(
            &mut self,
            value: ::std::boxed::Box<dyn bevy::reflect::Reflect>,
        ) -> ::core::result::Result<(), ::std::boxed::Box<dyn bevy::reflect::Reflect>> {
            *self = <dyn bevy::reflect::Reflect>::take(value)?;
            ::core::result::Result::Ok(())
        }
    }
    impl<T> bevy::reflect::Struct for ShuffleBag<T>
    where
        ShuffleBag<T>: ::core::any::Any + ::core::marker::Send + ::core::marker::Sync,
        Vec<T>: bevy::reflect::FromReflect
            + bevy::reflect::TypePath
            + bevy::reflect::MaybeTyped
            + bevy::reflect::__macro_exports::RegisterForReflection,
    {
        fn field(&self, name: &str) -> ::core::option::Option<&dyn bevy::reflect::PartialReflect> {
            match name {
                "full_collection" => ::core::option::Option::Some(&self.full_collection),
                "current_draft" => ::core::option::Option::Some(&self.current_draft),
                "last_pick" => ::core::option::Option::Some(&self.last_pick),
                _ => ::core::option::Option::None,
            }
        }
        fn field_mut(
            &mut self,
            name: &str,
        ) -> ::core::option::Option<&mut dyn bevy::reflect::PartialReflect> {
            match name {
                "full_collection" => ::core::option::Option::Some(&mut self.full_collection),
                "current_draft" => ::core::option::Option::Some(&mut self.current_draft),
                "last_pick" => ::core::option::Option::Some(&mut self.last_pick),
                _ => ::core::option::Option::None,
            }
        }
        fn field_at(
            &self,
            index: usize,
        ) -> ::core::option::Option<&dyn bevy::reflect::PartialReflect> {
            match index {
                0usize => ::core::option::Option::Some(&self.full_collection),
                1usize => ::core::option::Option::Some(&self.current_draft),
                2usize => ::core::option::Option::Some(&self.last_pick),
                _ => ::core::option::Option::None,
            }
        }
        fn field_at_mut(
            &mut self,
            index: usize,
        ) -> ::core::option::Option<&mut dyn bevy::reflect::PartialReflect> {
            match index {
                0usize => ::core::option::Option::Some(&mut self.full_collection),
                1usize => ::core::option::Option::Some(&mut self.current_draft),
                2usize => ::core::option::Option::Some(&mut self.last_pick),
                _ => ::core::option::Option::None,
            }
        }
        fn name_at(&self, index: usize) -> ::core::option::Option<&str> {
            match index {
                0usize => ::core::option::Option::Some("full_collection"),
                1usize => ::core::option::Option::Some("current_draft"),
                2usize => ::core::option::Option::Some("last_pick"),
                _ => ::core::option::Option::None,
            }
        }
        fn field_len(&self) -> usize {
            3usize
        }
        fn iter_fields(&self) -> bevy::reflect::FieldIter {
            bevy::reflect::FieldIter::new(self)
        }
        fn clone_dynamic(&self) -> bevy::reflect::DynamicStruct {
            let mut dynamic: bevy::reflect::DynamicStruct = ::core::default::Default::default();
            dynamic.set_represented_type(bevy::reflect::PartialReflect::get_represented_type_info(
                self,
            ));
            dynamic.insert_boxed(
                "full_collection",
                bevy::reflect::PartialReflect::clone_value(&self.full_collection),
            );
            dynamic.insert_boxed(
                "current_draft",
                bevy::reflect::PartialReflect::clone_value(&self.current_draft),
            );
            dynamic.insert_boxed(
                "last_pick",
                bevy::reflect::PartialReflect::clone_value(&self.last_pick),
            );
            dynamic
        }
    }
    impl<T> bevy::reflect::PartialReflect for ShuffleBag<T>
    where
        ShuffleBag<T>: ::core::any::Any + ::core::marker::Send + ::core::marker::Sync,
        Vec<T>: bevy::reflect::FromReflect
            + bevy::reflect::TypePath
            + bevy::reflect::MaybeTyped
            + bevy::reflect::__macro_exports::RegisterForReflection,
    {
        #[inline]
        fn get_represented_type_info(
            &self,
        ) -> ::core::option::Option<&'static bevy::reflect::TypeInfo> {
            ::core::option::Option::Some(<Self as bevy::reflect::Typed>::type_info())
        }
        #[inline]
        fn clone_value(&self) -> ::std::boxed::Box<dyn bevy::reflect::PartialReflect> {
            ::std::boxed::Box::new(bevy::reflect::Struct::clone_dynamic(self))
        }
        #[inline]
        fn try_apply(
            &mut self,
            value: &dyn bevy::reflect::PartialReflect,
        ) -> ::core::result::Result<(), bevy::reflect::ApplyError> {
            if let bevy::reflect::ReflectRef::Struct(struct_value) =
                bevy::reflect::PartialReflect::reflect_ref(value)
            {
                for (i, value) in ::core::iter::Iterator::enumerate(
                    bevy::reflect::Struct::iter_fields(struct_value),
                ) {
                    let name = bevy::reflect::Struct::name_at(struct_value, i).unwrap();
                    if let ::core::option::Option::Some(v) =
                        bevy::reflect::Struct::field_mut(self, name)
                    {
                        bevy::reflect::PartialReflect::try_apply(v, value)?;
                    }
                }
            } else {
                return ::core::result::Result::Err(bevy::reflect::ApplyError::MismatchedKinds {
                    from_kind: bevy::reflect::PartialReflect::reflect_kind(value),
                    to_kind: bevy::reflect::ReflectKind::Struct,
                });
            }
            ::core::result::Result::Ok(())
        }
        #[inline]
        fn reflect_kind(&self) -> bevy::reflect::ReflectKind {
            bevy::reflect::ReflectKind::Struct
        }
        #[inline]
        fn reflect_ref(&self) -> bevy::reflect::ReflectRef {
            bevy::reflect::ReflectRef::Struct(self)
        }
        #[inline]
        fn reflect_mut(&mut self) -> bevy::reflect::ReflectMut {
            bevy::reflect::ReflectMut::Struct(self)
        }
        #[inline]
        fn reflect_owned(self: ::std::boxed::Box<Self>) -> bevy::reflect::ReflectOwned {
            bevy::reflect::ReflectOwned::Struct(self)
        }
        #[inline]
        fn try_into_reflect(
            self: ::std::boxed::Box<Self>,
        ) -> ::core::result::Result<
            ::std::boxed::Box<dyn bevy::reflect::Reflect>,
            ::std::boxed::Box<dyn bevy::reflect::PartialReflect>,
        > {
            ::core::result::Result::Ok(self)
        }
        #[inline]
        fn try_as_reflect(&self) -> ::core::option::Option<&dyn bevy::reflect::Reflect> {
            ::core::option::Option::Some(self)
        }
        #[inline]
        fn try_as_reflect_mut(
            &mut self,
        ) -> ::core::option::Option<&mut dyn bevy::reflect::Reflect> {
            ::core::option::Option::Some(self)
        }
        #[inline]
        fn into_partial_reflect(
            self: ::std::boxed::Box<Self>,
        ) -> ::std::boxed::Box<dyn bevy::reflect::PartialReflect> {
            self
        }
        #[inline]
        fn as_partial_reflect(&self) -> &dyn bevy::reflect::PartialReflect {
            self
        }
        #[inline]
        fn as_partial_reflect_mut(&mut self) -> &mut dyn bevy::reflect::PartialReflect {
            self
        }
        fn reflect_partial_eq(
            &self,
            value: &dyn bevy::reflect::PartialReflect,
        ) -> ::core::option::Option<bool> {
            (bevy::reflect::struct_partial_eq)(self, value)
        }
    }
    impl<T> bevy::reflect::FromReflect for ShuffleBag<T>
    where
        ShuffleBag<T>: ::core::any::Any + ::core::marker::Send + ::core::marker::Sync,
        Vec<T>: bevy::reflect::FromReflect
            + bevy::reflect::TypePath
            + bevy::reflect::MaybeTyped
            + bevy::reflect::__macro_exports::RegisterForReflection,
    {
        fn from_reflect(
            reflect: &dyn bevy::reflect::PartialReflect,
        ) -> ::core::option::Option<Self> {
            if let bevy::reflect::ReflectRef::Struct(__ref_struct) =
                bevy::reflect::PartialReflect::reflect_ref(reflect)
            {
                let __this = Self {
                    full_collection: (|| {
                        <Vec<T> as bevy::reflect::FromReflect>::from_reflect(
                            bevy::reflect::Struct::field(__ref_struct, "full_collection")?,
                        )
                    })()?,
                    current_draft: (|| {
                        <Vec<usize> as bevy::reflect::FromReflect>::from_reflect(
                            bevy::reflect::Struct::field(__ref_struct, "current_draft")?,
                        )
                    })()?,
                    last_pick: (|| {
                        <Option<usize> as bevy::reflect::FromReflect>::from_reflect(
                            bevy::reflect::Struct::field(__ref_struct, "last_pick")?,
                        )
                    })()?,
                };
                ::core::option::Option::Some(__this)
            } else {
                ::core::option::Option::None
            }
        }
    }
};

#[cfg(test)]
mod tests {
    use super::*;
    use bevy::reflect::Typed;
    use paste::paste;

    #[test]
    fn fails_to_create_empty_shuffle_bag() {
        let mut rng = rand::thread_rng();
        let bag = ShuffleBag::<usize>::try_new(vec![], &mut rng);
        assert!(bag.is_none());
    }

    #[test]
    fn picks_same_item_from_singular_bag() {
        let mut rng = rand::thread_rng();
        let mut bag = ShuffleBag::<usize>::try_new(vec![1], &mut rng).unwrap();
        for _ in 0..100 {
            assert_eq!(*bag.pick(&mut rng), 1);
        }
    }

    #[test]
    fn picks_all_items_from_bag() {
        let mut rng = rand::thread_rng();
        let mut bag = ShuffleBag::<usize>::try_new(vec![1, 2, 3], &mut rng).unwrap();
        let mut picked = Vec::new();
        for _ in 0..99 {
            let item = bag.pick(&mut rng);
            picked.push(*item);
        }
        assert_eq!(picked.len(), 99, "expected 99 items, got {}", picked.len());
        let ones = picked.iter().filter(|&&item| item == 1).count();
        let twos = picked.iter().filter(|&&item| item == 2).count();
        let threes = picked.iter().filter(|&&item| item == 3).count();
        assert!(ones == 33, "ones: {} (expected 33)", ones);
        assert!(twos == 33, "twos: {} (expected 33)", twos);
        assert!(threes == 33, "threes: {} (expected 33)", threes);
    }

    #[test]
    fn never_picks_the_same_item_twice() {
        let mut rng = rand::thread_rng();
        let mut bag = ShuffleBag::<usize>::try_new(vec![1, 2, 3], &mut rng).unwrap();
        let mut last_pick = None;
        for _ in 0..1000 {
            let pick = *bag.pick(&mut rng);
            assert_ne!(Some(pick), last_pick);
            last_pick = Some(pick);
        }
    }

    assert_implements_type!(
        Eq,
        Hash,
        Clone,
        Debug,
        PartialEq,
        PartialReflect,
        Reflect,
        Struct,
        TypePath,
        Typed,
        Component,
        Resource
    );

    #[derive(Asset, TypePath)]
    struct _TestAsset {
        #[dependency]
        shuffle_bag: ShuffleBag<Handle<()>>,
    }

    macro_rules! assert_implements_type {
        ($($name:ident),*) => {
            $(
                paste! {
                    #[test]
                    #[allow(non_snake_case)]
                    fn [<is_ $name>]() {
                    fn accept_type<T: $name>(_a: T) {}
                        let mut rng = rand::thread_rng();
                        let bag = ShuffleBag::try_new(vec![1, 2, 3], &mut rng).unwrap();
                        accept_type(bag);
                    }
                }
            )*
        };
    }
    use assert_implements_type;
}