Move EntityHash related types into bevy_ecs (#11498)

# Objective

Reduce the size of `bevy_utils`
(https://github.com/bevyengine/bevy/issues/11478)

## Solution

Move `EntityHash` related types into `bevy_ecs`. This also allows us
access to `Entity`, which means we no longer need `EntityHashMap`'s
first generic argument.

---

## Changelog

- Moved `bevy::utils::{EntityHash, EntityHasher, EntityHashMap,
EntityHashSet}` into `bevy::ecs::entity::hash` .
- Removed `EntityHashMap`'s first generic argument. It is now hardcoded
to always be `Entity`.

## Migration Guide

- Uses of `bevy::utils::{EntityHash, EntityHasher, EntityHashMap,
EntityHashSet}` now have to be imported from `bevy::ecs::entity::hash`.
- Uses of `EntityHashMap` no longer have to specify the first generic
parameter. It is now hardcoded to always be `Entity`.

benches/Cargo.toml

@@ -63,6 +63,6 @@ path = "benches/bevy_math/bezier.rs"
 harness = false
 
 [[bench]]
-name = "utils"
-path = "benches/bevy_utils/entity_hash.rs"
+name = "entity_hash"
+path = "benches/bevy_ecs/world/entity_hash.rs"
 harness = false

benches/benches/bevy_ecs/world/entity_hash.rs

@@ -1,5 +1,4 @@
-use bevy_ecs::entity::Entity;
-use bevy_utils::EntityHashSet;
+use bevy_ecs::entity::{Entity, EntityHashMap, EntityHashSet};
 use criterion::{criterion_group, criterion_main, BenchmarkId, Criterion, Throughput};
 use rand::{Rng, SeedableRng};
 use rand_chacha::ChaCha8Rng;
@@ -28,7 +27,7 @@ fn make_entity(rng: &mut impl Rng, size: usize) -> Entity {
     e
 }
 
-fn entity_set_build_and_lookup(c: &mut Criterion) {
+pub fn entity_set_build_and_lookup(c: &mut Criterion) {
     let mut group = c.benchmark_group("entity_hash");
     for size in SIZES {
         // Get some random-but-consistent entities to use for all the benches below.

benches/benches/bevy_ecs/world/mod.rs

@@ -1,13 +1,17 @@
 use criterion::criterion_group;
 
 mod commands;
-mod spawn;
-mod world_get;
-
 use commands::*;
+
+mod spawn;
 use spawn::*;
+
+mod world_get;
 use world_get::*;
 
+mod entity_hash;
+use entity_hash::*;
+
 criterion_group!(
     world_benches,
     empty_commands,
@@ -30,4 +34,5 @@ criterion_group!(
     query_get_many::<2>,
     query_get_many::<5>,
     query_get_many::<10>,
+    entity_set_build_and_lookup
 );

crates/bevy_ecs/Cargo.toml

@@ -32,6 +32,7 @@ thiserror = "1.0"
 
 [dev-dependencies]
 rand = "0.8"
+static_assertions = "1.1.0"
 
 [[example]]
 name = "events"

crates/bevy_ecs/src/entity/hash.rs

@@ -0,0 +1,99 @@
+use std::hash::{BuildHasher, Hasher};
+
+#[cfg(feature = "bevy_reflect")]
+use bevy_reflect::Reflect;
+use bevy_utils::hashbrown;
+
+use super::Entity;
+
+/// A [`BuildHasher`] that results in a [`EntityHasher`].
+#[derive(Default, Clone)]
+#[cfg_attr(feature = "bevy_reflect", derive(Reflect))]
+pub struct EntityHash;
+
+impl BuildHasher for EntityHash {
+    type Hasher = EntityHasher;
+
+    fn build_hasher(&self) -> Self::Hasher {
+        Self::Hasher::default()
+    }
+}
+
+/// A very fast hash that is only designed to work on generational indices
+/// like [`Entity`]. It will panic if attempting to hash a type containing
+/// non-u64 fields.
+///
+/// This is heavily optimized for typical cases, where you have mostly live
+/// entities, and works particularly well for contiguous indices.
+///
+/// If you have an unusual case -- say all your indices are multiples of 256
+/// or most of the entities are dead generations -- then you might want also to
+/// try [`AHasher`](bevy_utils::AHasher) for a slower hash computation but fewer lookup conflicts.
+#[derive(Debug, Default)]
+pub struct EntityHasher {
+    hash: u64,
+}
+
+impl Hasher for EntityHasher {
+    #[inline]
+    fn finish(&self) -> u64 {
+        self.hash
+    }
+
+    fn write(&mut self, _bytes: &[u8]) {
+        panic!("EntityHasher can only hash u64 fields.");
+    }
+
+    #[inline]
+    fn write_u64(&mut self, bits: u64) {
+        // SwissTable (and thus `hashbrown`) cares about two things from the hash:
+        // - H1: low bits (masked by `2ⁿ-1`) to pick the slot in which to store the item
+        // - H2: high 7 bits are used to SIMD optimize hash collision probing
+        // For more see <https://abseil.io/about/design/swisstables#metadata-layout>
+
+        // This hash function assumes that the entity ids are still well-distributed,
+        // so for H1 leaves the entity id alone in the low bits so that id locality
+        // will also give memory locality for things spawned together.
+        // For H2, take advantage of the fact that while multiplication doesn't
+        // spread entropy to the low bits, it's incredibly good at spreading it
+        // upward, which is exactly where we need it the most.
+
+        // While this does include the generation in the output, it doesn't do so
+        // *usefully*.  H1 won't care until you have over 3 billion entities in
+        // the table, and H2 won't care until something hits generation 33 million.
+        // Thus the comment suggesting that this is best for live entities,
+        // where there won't be generation conflicts where it would matter.
+
+        // The high 32 bits of this are ⅟φ for Fibonacci hashing.  That works
+        // particularly well for hashing for the same reason as described in
+        // <https://extremelearning.com.au/unreasonable-effectiveness-of-quasirandom-sequences/>
+        // It loses no information because it has a modular inverse.
+        // (Specifically, `0x144c_bc89_u32 * 0x9e37_79b9_u32 == 1`.)
+        //
+        // The low 32 bits make that part of the just product a pass-through.
+        const UPPER_PHI: u64 = 0x9e37_79b9_0000_0001;
+
+        // This is `(MAGIC * index + generation) << 32 + index`, in a single instruction.
+        self.hash = bits.wrapping_mul(UPPER_PHI);
+    }
+}
+
+/// A [`HashMap`](hashbrown::HashMap) pre-configured to use [`EntityHash`] hashing.
+pub type EntityHashMap<V> = hashbrown::HashMap<Entity, V, EntityHash>;
+
+/// A [`HashSet`](hashbrown::HashSet) pre-configured to use [`EntityHash`] hashing.
+pub type EntityHashSet = hashbrown::HashSet<Entity, EntityHash>;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[cfg(feature = "bevy_reflect")]
+    use bevy_reflect::Reflect;
+    use static_assertions::assert_impl_all;
+
+    // Check that the HashMaps are Clone if the key/values are Clone
+    assert_impl_all!(EntityHashMap::<usize>: Clone);
+    // EntityHashMap should implement Reflect
+    #[cfg(feature = "bevy_reflect")]
+    assert_impl_all!(EntityHashMap::<i32>: Reflect);
+}

crates/bevy_ecs/src/entity/map_entities.rs

@@ -3,7 +3,8 @@ use crate::{
     identifier::masks::{IdentifierMask, HIGH_MASK},
     world::World,
 };
-use bevy_utils::EntityHashMap;
+
+use super::EntityHashMap;
 
 /// Operation to map all contained [`Entity`] fields in a type to new values.
 ///
@@ -11,7 +12,7 @@ use bevy_utils::EntityHashMap;
 /// as references in components copied from another world will be invalid. This trait
 /// allows defining custom mappings for these references via [`EntityMappers`](EntityMapper), which
 /// inject the entity mapping strategy between your `MapEntities` type and the current world
-/// (usually by using an [`EntityHashMap<Entity, Entity>`] between source entities and entities in the
+/// (usually by using an [`EntityHashMap<Entity>`] between source entities and entities in the
 /// current world).
 ///
 /// Implementing this trait correctly is required for properly loading components
@@ -47,7 +48,7 @@ pub trait MapEntities {
 
 /// An implementor of this trait knows how to map an [`Entity`] into another [`Entity`].
 ///
-/// Usually this is done by using an [`EntityHashMap<Entity, Entity>`] to map source entities
+/// Usually this is done by using an [`EntityHashMap<Entity>`] to map source entities
 /// (mapper inputs) to the current world's entities (mapper outputs).
 ///
 /// More generally, this can be used to map [`Entity`] references between any two [`Worlds`](World).
@@ -56,10 +57,10 @@ pub trait MapEntities {
 ///
 /// ```
 /// # use bevy_ecs::entity::{Entity, EntityMapper};
-/// # use bevy_utils::EntityHashMap;
+/// # use bevy_ecs::entity::EntityHashMap;
 /// #
 /// pub struct SimpleEntityMapper {
-///   map: EntityHashMap<Entity, Entity>,
+///   map: EntityHashMap<Entity>,
 /// }
 ///
 /// // Example implementation of EntityMapper where we map an entity to another entity if it exists
@@ -97,7 +98,7 @@ impl EntityMapper for SceneEntityMapper<'_> {
     }
 }
 
-/// A wrapper for [`EntityHashMap<Entity, Entity>`], augmenting it with the ability to allocate new [`Entity`] references in a destination
+/// A wrapper for [`EntityHashMap<Entity>`], augmenting it with the ability to allocate new [`Entity`] references in a destination
 /// world. These newly allocated references are guaranteed to never point to any living entity in that world.
 ///
 /// References are allocated by returning increasing generations starting from an internally initialized base
@@ -110,9 +111,9 @@ pub struct SceneEntityMapper<'m> {
     /// or over the network. This is required as [`Entity`] identifiers are opaque; you cannot and do not want to reuse
     /// identifiers directly.
     ///
-    /// On its own, a [`EntityHashMap<Entity, Entity>`] is not capable of allocating new entity identifiers, which is needed to map references
+    /// On its own, a [`EntityHashMap<Entity>`] is not capable of allocating new entity identifiers, which is needed to map references
     /// to entities that lie outside the source entity set. This functionality can be accessed through [`SceneEntityMapper::world_scope()`].
-    map: &'m mut EntityHashMap<Entity, Entity>,
+    map: &'m mut EntityHashMap<Entity>,
     /// A base [`Entity`] used to allocate new references.
     dead_start: Entity,
     /// The number of generations this mapper has allocated thus far.
@@ -129,18 +130,18 @@ impl<'m> SceneEntityMapper<'m> {
         self.map_entity(entity)
     }
 
-    /// Gets a reference to the underlying [`EntityHashMap<Entity, Entity>`].
-    pub fn get_map(&'m self) -> &'m EntityHashMap<Entity, Entity> {
+    /// Gets a reference to the underlying [`EntityHashMap<Entity>`].
+    pub fn get_map(&'m self) -> &'m EntityHashMap<Entity> {
         self.map
     }
 
-    /// Gets a mutable reference to the underlying [`EntityHashMap<Entity, Entity>`].
-    pub fn get_map_mut(&'m mut self) -> &'m mut EntityHashMap<Entity, Entity> {
+    /// Gets a mutable reference to the underlying [`EntityHashMap<Entity>`].
+    pub fn get_map_mut(&'m mut self) -> &'m mut EntityHashMap<Entity> {
         self.map
     }
 
     /// Creates a new [`SceneEntityMapper`], spawning a temporary base [`Entity`] in the provided [`World`]
-    fn new(map: &'m mut EntityHashMap<Entity, Entity>, world: &mut World) -> Self {
+    fn new(map: &'m mut EntityHashMap<Entity>, world: &mut World) -> Self {
         Self {
             map,
             // SAFETY: Entities data is kept in a valid state via `EntityMapper::world_scope`
@@ -160,14 +161,14 @@ impl<'m> SceneEntityMapper<'m> {
         assert!(entities.reserve_generations(self.dead_start.index(), self.generations));
     }
 
-    /// Creates an [`SceneEntityMapper`] from a provided [`World`] and [`EntityHashMap<Entity, Entity>`], then calls the
+    /// Creates an [`SceneEntityMapper`] from a provided [`World`] and [`EntityHashMap<Entity>`], then calls the
     /// provided function with it. This allows one to allocate new entity references in this [`World`] that are
     /// guaranteed to never point at a living entity now or in the future. This functionality is useful for safely
     /// mapping entity identifiers that point at entities outside the source world. The passed function, `f`, is called
     /// within the scope of this world. Its return value is then returned from `world_scope` as the generic type
     /// parameter `R`.
     pub fn world_scope<R>(
-        entity_map: &'m mut EntityHashMap<Entity, Entity>,
+        entity_map: &'m mut EntityHashMap<Entity>,
         world: &mut World,
         f: impl FnOnce(&mut World, &mut Self) -> R,
     ) -> R {
@@ -180,10 +181,8 @@ impl<'m> SceneEntityMapper<'m> {
 
 #[cfg(test)]
 mod tests {
-    use bevy_utils::EntityHashMap;
-
     use crate::{
-        entity::{Entity, EntityMapper, SceneEntityMapper},
+        entity::{Entity, EntityHashMap, EntityMapper, SceneEntityMapper},
         world::World,
     };
 

crates/bevy_ecs/src/entity/mod.rs

@@ -36,9 +36,14 @@
 //! [`EntityWorldMut::insert`]: crate::world::EntityWorldMut::insert
 //! [`EntityWorldMut::remove`]: crate::world::EntityWorldMut::remove
 mod map_entities;
+#[cfg(feature = "bevy_reflect")]
+use bevy_reflect::{Reflect, ReflectDeserialize, ReflectSerialize};
+pub use map_entities::*;
+
+mod hash;
+pub use hash::*;
 
 use bevy_utils::tracing::warn;
-pub use map_entities::*;
 
 use crate::{
     archetype::{ArchetypeId, ArchetypeRow},
@@ -123,6 +128,11 @@ type IdCursor = isize;
 /// [`Query::get`]: crate::system::Query::get
 /// [`World`]: crate::world::World
 #[derive(Clone, Copy)]
+#[cfg_attr(feature = "bevy_reflect", derive(Reflect))]
+#[cfg_attr(
+    feature = "bevy_reflect",
+    reflect_value(Hash, PartialEq, Serialize, Deserialize)
+)]
 // Alignment repr necessary to allow LLVM to better output
 // optimised codegen for `to_bits`, `PartialEq` and `Ord`.
 #[repr(C, align(8))]
@@ -218,7 +228,7 @@ impl Entity {
     /// // ... replace the entities with valid ones.
     /// ```
     ///
-    /// Deriving [`Reflect`](bevy_reflect::Reflect) for a component that has an `Entity` field:
+    /// Deriving [`Reflect`] for a component that has an `Entity` field:
     ///
     /// ```no_run
     /// # use bevy_ecs::{prelude::*, component::*};
@@ -1092,7 +1102,7 @@ mod tests {
     #[test]
     fn entity_hash_keeps_similar_ids_together() {
         use std::hash::BuildHasher;
-        let hash = bevy_utils::EntityHash;
+        let hash = EntityHash;
 
         let first_id = 0xC0FFEE << 8;
         let first_hash = hash.hash_one(Entity::from_raw(first_id));
@@ -1107,7 +1117,8 @@ mod tests {
     #[test]
     fn entity_hash_id_bitflip_affects_high_7_bits() {
         use std::hash::BuildHasher;
-        let hash = bevy_utils::EntityHash;
+
+        let hash = EntityHash;
 
         let first_id = 0xC0FFEE;
         let first_hash = hash.hash_one(Entity::from_raw(first_id)) >> 57;

crates/bevy_ecs/src/reflect/map_entities.rs

@@ -1,10 +1,9 @@
 use crate::{
     component::Component,
-    entity::{Entity, MapEntities, SceneEntityMapper},
+    entity::{Entity, EntityHashMap, MapEntities, SceneEntityMapper},
     world::World,
 };
 use bevy_reflect::FromType;
-use bevy_utils::EntityHashMap;
 
 /// For a specific type of component, this maps any fields with values of type [`Entity`] to a new world.
 /// Since a given `Entity` ID is only valid for the world it came from, when performing deserialization
@@ -18,33 +17,29 @@ pub struct ReflectMapEntities {
 }
 
 impl ReflectMapEntities {
-    /// A general method for applying [`MapEntities`] behavior to all elements in an [`EntityHashMap<Entity, Entity>`].
+    /// A general method for applying [`MapEntities`] behavior to all elements in an [`EntityHashMap<Entity>`].
     ///
-    /// Be mindful in its usage: Works best in situations where the entities in the [`EntityHashMap<Entity, Entity>`] are newly
+    /// Be mindful in its usage: Works best in situations where the entities in the [`EntityHashMap<Entity>`] are newly
     /// created, before systems have a chance to add new components. If some of the entities referred to
-    /// by the [`EntityHashMap<Entity, Entity>`] might already contain valid entity references, you should use [`map_entities`](Self::map_entities).
+    /// by the [`EntityHashMap<Entity>`] might already contain valid entity references, you should use [`map_entities`](Self::map_entities).
     ///
     /// An example of this: A scene can be loaded with `Parent` components, but then a `Parent` component can be added
     /// to these entities after they have been loaded. If you reload the scene using [`map_all_entities`](Self::map_all_entities), those `Parent`
     /// components with already valid entity references could be updated to point at something else entirely.
-    pub fn map_all_entities(
-        &self,
-        world: &mut World,
-        entity_map: &mut EntityHashMap<Entity, Entity>,
-    ) {
+    pub fn map_all_entities(&self, world: &mut World, entity_map: &mut EntityHashMap<Entity>) {
         SceneEntityMapper::world_scope(entity_map, world, self.map_all_entities);
     }
 
-    /// A general method for applying [`MapEntities`] behavior to elements in an [`EntityHashMap<Entity, Entity>`]. Unlike
+    /// A general method for applying [`MapEntities`] behavior to elements in an [`EntityHashMap<Entity>`]. Unlike
     /// [`map_all_entities`](Self::map_all_entities), this is applied to specific entities, not all values
-    /// in the [`EntityHashMap<Entity, Entity>`].
+    /// in the [`EntityHashMap<Entity>`].
     ///
     /// This is useful mostly for when you need to be careful not to update components that already contain valid entity
     /// values. See [`map_all_entities`](Self::map_all_entities) for more details.
     pub fn map_entities(
         &self,
         world: &mut World,
-        entity_map: &mut EntityHashMap<Entity, Entity>,
+        entity_map: &mut EntityHashMap<Entity>,
         entities: &[Entity],
     ) {
         SceneEntityMapper::world_scope(entity_map, world, |world, mapper| {

crates/bevy_ecs/src/reflect/mod.rs

@@ -3,8 +3,8 @@
 use std::ops::{Deref, DerefMut};
 
 use crate as bevy_ecs;
-use crate::{entity::Entity, system::Resource};
-use bevy_reflect::{impl_reflect_value, ReflectDeserialize, ReflectSerialize, TypeRegistryArc};
+use crate::system::Resource;
+use bevy_reflect::TypeRegistryArc;
 
 mod bundle;
 mod component;
@@ -40,5 +40,3 @@ impl DerefMut for AppTypeRegistry {
         &mut self.0
     }
 }
-
-impl_reflect_value!((in bevy_ecs) Entity(Hash, PartialEq, Serialize, Deserialize));

crates/bevy_gltf/src/loader.rs

@@ -4,6 +4,7 @@ use bevy_asset::{
 };
 use bevy_core::Name;
 use bevy_core_pipeline::prelude::Camera3dBundle;
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::{entity::Entity, world::World};
 use bevy_hierarchy::{BuildWorldChildren, WorldChildBuilder};
 use bevy_log::{error, warn};
@@ -33,7 +34,7 @@ use bevy_scene::Scene;
 #[cfg(not(target_arch = "wasm32"))]
 use bevy_tasks::IoTaskPool;
 use bevy_transform::components::Transform;
-use bevy_utils::{EntityHashMap, HashMap, HashSet};
+use bevy_utils::{HashMap, HashSet};
 use gltf::{
     accessor::Iter,
     mesh::{util::ReadIndices, Mode},
@@ -930,7 +931,7 @@ fn load_node(
     load_context: &mut LoadContext,
     settings: &GltfLoaderSettings,
     node_index_to_entity_map: &mut HashMap<usize, Entity>,
-    entity_to_skin_index_map: &mut EntityHashMap<Entity, usize>,
+    entity_to_skin_index_map: &mut EntityHashMap<usize>,
     active_camera_found: &mut bool,
     parent_transform: &Transform,
 ) -> Result<(), GltfError> {

crates/bevy_pbr/src/bundle.rs

@@ -3,7 +3,8 @@ use crate::{
     StandardMaterial,
 };
 use bevy_asset::Handle;
-use bevy_ecs::{bundle::Bundle, component::Component, prelude::Entity, reflect::ReflectComponent};
+use bevy_ecs::entity::EntityHashMap;
+use bevy_ecs::{bundle::Bundle, component::Component, reflect::ReflectComponent};
 use bevy_reflect::Reflect;
 use bevy_render::{
     mesh::Mesh,
@@ -11,7 +12,6 @@ use bevy_render::{
     view::{InheritedVisibility, ViewVisibility, Visibility, VisibleEntities},
 };
 use bevy_transform::components::{GlobalTransform, Transform};
-use bevy_utils::EntityHashMap;
 
 /// A component bundle for PBR entities with a [`Mesh`] and a [`StandardMaterial`].
 pub type PbrBundle = MaterialMeshBundle<StandardMaterial>;
@@ -75,7 +75,7 @@ impl CubemapVisibleEntities {
 pub struct CascadesVisibleEntities {
     /// Map of view entity to the visible entities for each cascade frustum.
     #[reflect(ignore)]
-    pub entities: EntityHashMap<Entity, Vec<VisibleEntities>>,
+    pub entities: EntityHashMap<Vec<VisibleEntities>>,
 }
 
 /// A component bundle for [`PointLight`] entities.

crates/bevy_pbr/src/light.rs

@@ -1,5 +1,6 @@
 use std::collections::HashSet;
 
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::prelude::*;
 use bevy_math::{
     AspectRatio, Mat4, UVec2, UVec3, Vec2, Vec3, Vec3A, Vec3Swizzles, Vec4, Vec4Swizzles,
@@ -16,7 +17,7 @@ use bevy_render::{
     view::{InheritedVisibility, RenderLayers, ViewVisibility, VisibleEntities},
 };
 use bevy_transform::components::{GlobalTransform, Transform};
-use bevy_utils::{tracing::warn, EntityHashMap};
+use bevy_utils::tracing::warn;
 
 use crate::*;
 
@@ -390,7 +391,7 @@ impl From<CascadeShadowConfigBuilder> for CascadeShadowConfig {
 #[reflect(Component)]
 pub struct Cascades {
     /// Map from a view to the configuration of each of its [`Cascade`]s.
-    pub(crate) cascades: EntityHashMap<Entity, Vec<Cascade>>,
+    pub(crate) cascades: EntityHashMap<Vec<Cascade>>,
 }
 
 #[derive(Clone, Debug, Default, Reflect)]

crates/bevy_pbr/src/light_probe/mod.rs

@@ -159,6 +159,7 @@ pub struct LightProbesUniform {
     intensity_for_view: f32,
 }
 
+/// A GPU buffer that stores information about all light probes.
 #[derive(Resource, Default, Deref, DerefMut)]
 pub struct LightProbesBuffer(DynamicUniformBuffer<LightProbesUniform>);
 

crates/bevy_pbr/src/lightmap/mod.rs

@@ -30,6 +30,7 @@
 
 use bevy_app::{App, Plugin};
 use bevy_asset::{load_internal_asset, AssetId, Handle};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::{
     component::Component,
     entity::Entity,
@@ -43,7 +44,7 @@ use bevy_render::{
     mesh::Mesh, render_asset::RenderAssets, render_resource::Shader, texture::Image,
     view::ViewVisibility, Extract, ExtractSchedule, RenderApp,
 };
-use bevy_utils::{EntityHashMap, HashSet};
+use bevy_utils::HashSet;
 
 use crate::RenderMeshInstances;
 
@@ -104,7 +105,7 @@ pub struct RenderLightmaps {
     ///
     /// Entities without lightmaps, or for which the mesh or lightmap isn't
     /// loaded, won't have entries in this table.
-    pub(crate) render_lightmaps: EntityHashMap<Entity, RenderLightmap>,
+    pub(crate) render_lightmaps: EntityHashMap<RenderLightmap>,
 
     /// All active lightmap images in the scene.
     ///

crates/bevy_pbr/src/render/light.rs

@@ -1,4 +1,5 @@
 use bevy_core_pipeline::core_3d::{Transparent3d, CORE_3D_DEPTH_FORMAT};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::prelude::*;
 use bevy_math::{Mat4, UVec3, UVec4, Vec2, Vec3, Vec3Swizzles, Vec4, Vec4Swizzles};
 use bevy_render::{
@@ -21,7 +22,6 @@ use bevy_utils::tracing::info_span;
 use bevy_utils::{
     nonmax::NonMaxU32,
     tracing::{error, warn},
-    EntityHashMap,
 };
 use std::{hash::Hash, num::NonZeroU64, ops::Range};
 
@@ -50,8 +50,8 @@ pub struct ExtractedDirectionalLight {
     shadow_depth_bias: f32,
     shadow_normal_bias: f32,
     cascade_shadow_config: CascadeShadowConfig,
-    cascades: EntityHashMap<Entity, Vec<Cascade>>,
-    frusta: EntityHashMap<Entity, Vec<Frustum>>,
+    cascades: EntityHashMap<Vec<Cascade>>,
+    frusta: EntityHashMap<Vec<Frustum>>,
     render_layers: RenderLayers,
 }
 
@@ -586,7 +586,7 @@ pub const CLUSTERED_FORWARD_STORAGE_BUFFER_COUNT: u32 = 3;
 #[derive(Resource)]
 pub struct GlobalLightMeta {
     pub gpu_point_lights: GpuPointLights,
-    pub entity_to_index: EntityHashMap<Entity, usize>,
+    pub entity_to_index: EntityHashMap<usize>,
 }
 
 impl FromWorld for GlobalLightMeta {

crates/bevy_pbr/src/render/mesh.rs

@@ -10,6 +10,7 @@ use bevy_core_pipeline::{
     deferred::{AlphaMask3dDeferred, Opaque3dDeferred},
 };
 use bevy_derive::{Deref, DerefMut};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::{
     prelude::*,
     query::ROQueryItem,
@@ -33,7 +34,7 @@ use bevy_render::{
     Extract, ExtractSchedule, Render, RenderApp, RenderSet,
 };
 use bevy_transform::components::GlobalTransform;
-use bevy_utils::{tracing::error, EntityHashMap, Entry, HashMap, Hashed};
+use bevy_utils::{tracing::error, Entry, HashMap, Hashed};
 use std::cell::Cell;
 use thread_local::ThreadLocal;
 
@@ -254,7 +255,7 @@ pub struct RenderMeshInstance {
 }
 
 #[derive(Default, Resource, Deref, DerefMut)]
-pub struct RenderMeshInstances(EntityHashMap<Entity, RenderMeshInstance>);
+pub struct RenderMeshInstances(EntityHashMap<RenderMeshInstance>);
 
 pub fn extract_meshes(
     mut render_mesh_instances: ResMut<RenderMeshInstances>,

crates/bevy_pbr/src/render/morph.rs

@@ -1,6 +1,7 @@
 use std::{iter, mem};
 
 use bevy_derive::{Deref, DerefMut};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::prelude::*;
 use bevy_render::{
     batching::NoAutomaticBatching,
@@ -10,7 +11,6 @@ use bevy_render::{
     view::ViewVisibility,
     Extract,
 };
-use bevy_utils::EntityHashMap;
 use bytemuck::Pod;
 
 #[derive(Component)]
@@ -19,7 +19,7 @@ pub struct MorphIndex {
 }
 
 #[derive(Default, Resource, Deref, DerefMut)]
-pub struct MorphIndices(EntityHashMap<Entity, MorphIndex>);
+pub struct MorphIndices(EntityHashMap<MorphIndex>);
 
 #[derive(Resource)]
 pub struct MorphUniform {

crates/bevy_pbr/src/render/skin.rs

@@ -1,5 +1,6 @@
 use bevy_asset::Assets;
 use bevy_derive::{Deref, DerefMut};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::prelude::*;
 use bevy_math::Mat4;
 use bevy_render::{
@@ -11,7 +12,6 @@ use bevy_render::{
     Extract,
 };
 use bevy_transform::prelude::GlobalTransform;
-use bevy_utils::EntityHashMap;
 
 /// Maximum number of joints supported for skinned meshes.
 pub const MAX_JOINTS: usize = 256;
@@ -31,7 +31,7 @@ impl SkinIndex {
 }
 
 #[derive(Default, Resource, Deref, DerefMut)]
-pub struct SkinIndices(EntityHashMap<Entity, SkinIndex>);
+pub struct SkinIndices(EntityHashMap<SkinIndex>);
 
 // Notes on implementation: see comment on top of the `extract_skins` system.
 #[derive(Resource)]

crates/bevy_reflect/src/impls/std.rs

@@ -80,7 +80,6 @@ impl_reflect_value!(isize(
 impl_reflect_value!(f32(Debug, PartialEq, Serialize, Deserialize, Default));
 impl_reflect_value!(f64(Debug, PartialEq, Serialize, Deserialize, Default));
 impl_type_path!(str);
-impl_type_path!(::bevy_utils::EntityHash);
 impl_reflect_value!(::alloc::string::String(
     Debug,
     Hash,
@@ -1655,15 +1654,12 @@ mod tests {
         Enum, FromReflect, Reflect, ReflectSerialize, TypeInfo, TypeRegistry, Typed, VariantInfo,
         VariantType,
     };
+    use bevy_utils::HashMap;
     use bevy_utils::{Duration, Instant};
-    use bevy_utils::{EntityHashMap, HashMap};
     use static_assertions::assert_impl_all;
     use std::f32::consts::{PI, TAU};
     use std::path::Path;
 
-    // EntityHashMap should implement Reflect
-    assert_impl_all!(EntityHashMap<i32, i32>: Reflect);
-
     #[test]
     fn can_serialize_duration() {
         let mut type_registry = TypeRegistry::default();

crates/bevy_render/src/extract_instances.rs

@@ -10,11 +10,11 @@ use bevy_app::{App, Plugin};
 use bevy_asset::{Asset, AssetId, Handle};
 use bevy_derive::{Deref, DerefMut};
 use bevy_ecs::{
+    entity::EntityHashMap,
     prelude::Entity,
     query::{QueryFilter, QueryItem, ReadOnlyQueryData},
     system::{lifetimeless::Read, Query, ResMut, Resource},
 };
-use bevy_utils::EntityHashMap;
 
 use crate::{prelude::ViewVisibility, Extract, ExtractSchedule, RenderApp};
 
@@ -53,7 +53,7 @@ where
 
 /// Stores all extract instances of a type in the render world.
 #[derive(Resource, Deref, DerefMut)]
-pub struct ExtractedInstances<EI>(EntityHashMap<Entity, EI>)
+pub struct ExtractedInstances<EI>(EntityHashMap<EI>)
 where
     EI: ExtractInstance;
 

crates/bevy_render/src/primitives/mod.rs

@@ -1,9 +1,8 @@
 use std::borrow::Borrow;
 
-use bevy_ecs::{component::Component, prelude::Entity, reflect::ReflectComponent};
+use bevy_ecs::{component::Component, entity::EntityHashMap, reflect::ReflectComponent};
 use bevy_math::{Affine3A, Mat3A, Mat4, Vec3, Vec3A, Vec4, Vec4Swizzles};
 use bevy_reflect::Reflect;
-use bevy_utils::EntityHashMap;
 
 /// An axis-aligned bounding box, defined by:
 /// - a center,
@@ -323,7 +322,7 @@ impl CubemapFrusta {
 #[reflect(Component)]
 pub struct CascadesFrusta {
     #[reflect(ignore)]
-    pub frusta: EntityHashMap<Entity, Vec<Frustum>>,
+    pub frusta: EntityHashMap<Vec<Frustum>>,
 }
 
 #[cfg(test)]

crates/bevy_render/src/view/window/mod.rs

@@ -7,8 +7,8 @@ use crate::{
     Extract, ExtractSchedule, Render, RenderApp, RenderSet,
 };
 use bevy_app::{App, Plugin};
-use bevy_ecs::prelude::*;
-use bevy_utils::{default, tracing::debug, EntityHashMap, HashSet};
+use bevy_ecs::{entity::EntityHashMap, prelude::*};
+use bevy_utils::{default, tracing::debug, HashSet};
 use bevy_window::{
     CompositeAlphaMode, PresentMode, PrimaryWindow, RawHandleWrapper, Window, WindowClosed,
 };
@@ -92,11 +92,11 @@ impl ExtractedWindow {
 #[derive(Default, Resource)]
 pub struct ExtractedWindows {
     pub primary: Option<Entity>,
-    pub windows: EntityHashMap<Entity, ExtractedWindow>,
+    pub windows: EntityHashMap<ExtractedWindow>,
 }
 
 impl Deref for ExtractedWindows {
-    type Target = EntityHashMap<Entity, ExtractedWindow>;
+    type Target = EntityHashMap<ExtractedWindow>;
 
     fn deref(&self) -> &Self::Target {
         &self.windows
@@ -203,7 +203,7 @@ struct SurfaceData {
 
 #[derive(Resource, Default)]
 pub struct WindowSurfaces {
-    surfaces: EntityHashMap<Entity, SurfaceData>,
+    surfaces: EntityHashMap<SurfaceData>,
     /// List of windows that we have already called the initial `configure_surface` for
     configured_windows: HashSet<Entity>,
 }

crates/bevy_render/src/view/window/screenshot.rs

@@ -2,10 +2,9 @@ use std::{borrow::Cow, path::Path, sync::PoisonError};
 
 use bevy_app::Plugin;
 use bevy_asset::{load_internal_asset, Handle};
-use bevy_ecs::prelude::*;
+use bevy_ecs::{entity::EntityHashMap, prelude::*};
 use bevy_log::{error, info, info_span};
 use bevy_tasks::AsyncComputeTaskPool;
-use bevy_utils::EntityHashMap;
 use std::sync::Mutex;
 use thiserror::Error;
 use wgpu::{
@@ -33,7 +32,7 @@ pub type ScreenshotFn = Box<dyn FnOnce(Image) + Send + Sync>;
 #[derive(Resource, Default)]
 pub struct ScreenshotManager {
     // this is in a mutex to enable extraction with only an immutable reference
-    pub(crate) callbacks: Mutex<EntityHashMap<Entity, ScreenshotFn>>,
+    pub(crate) callbacks: Mutex<EntityHashMap<ScreenshotFn>>,
 }
 
 #[derive(Error, Debug)]

crates/bevy_scene/src/dynamic_scene.rs

@@ -1,11 +1,12 @@
 use crate::{ron, DynamicSceneBuilder, Scene, SceneSpawnError};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::{
     entity::Entity,
     reflect::{AppTypeRegistry, ReflectComponent, ReflectMapEntities},
     world::World,
 };
 use bevy_reflect::{Reflect, TypePath, TypeRegistryArc};
-use bevy_utils::{EntityHashMap, TypeIdMap};
+use bevy_utils::TypeIdMap;
 
 #[cfg(feature = "serialize")]
 use crate::serde::SceneSerializer;
@@ -65,7 +66,7 @@ impl DynamicScene {
     pub fn write_to_world_with(
         &self,
         world: &mut World,
-        entity_map: &mut EntityHashMap<Entity, Entity>,
+        entity_map: &mut EntityHashMap<Entity>,
         type_registry: &AppTypeRegistry,
     ) -> Result<(), SceneSpawnError> {
         let type_registry = type_registry.read();
@@ -163,7 +164,7 @@ impl DynamicScene {
     pub fn write_to_world(
         &self,
         world: &mut World,
-        entity_map: &mut EntityHashMap<Entity, Entity>,
+        entity_map: &mut EntityHashMap<Entity>,
     ) -> Result<(), SceneSpawnError> {
         let registry = world.resource::<AppTypeRegistry>().clone();
         self.write_to_world_with(world, entity_map, &registry)
@@ -191,9 +192,9 @@ where
 
 #[cfg(test)]
 mod tests {
+    use bevy_ecs::entity::EntityHashMap;
     use bevy_ecs::{reflect::AppTypeRegistry, system::Command, world::World};
     use bevy_hierarchy::{Parent, PushChild};
-    use bevy_utils::EntityHashMap;
 
     use crate::dynamic_scene_builder::DynamicSceneBuilder;
 

crates/bevy_scene/src/scene.rs

@@ -1,11 +1,11 @@
 use crate::{DynamicScene, InstanceInfo, SceneSpawnError};
 use bevy_asset::Asset;
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::{
     reflect::{AppTypeRegistry, ReflectComponent, ReflectMapEntities, ReflectResource},
     world::World,
 };
 use bevy_reflect::TypePath;
-use bevy_utils::EntityHashMap;
 
 /// To spawn a scene, you can use either:
 /// * [`SceneSpawner::spawn`](crate::SceneSpawner::spawn)

crates/bevy_scene/src/scene_spawner.rs

@@ -1,5 +1,6 @@
 use crate::{DynamicScene, Scene};
 use bevy_asset::{AssetEvent, AssetId, Assets, Handle};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::{
     entity::Entity,
     event::{Event, Events, ManualEventReader},
@@ -8,7 +9,7 @@ use bevy_ecs::{
     world::{Mut, World},
 };
 use bevy_hierarchy::{Parent, PushChild};
-use bevy_utils::{tracing::error, EntityHashMap, HashMap, HashSet};
+use bevy_utils::{tracing::error, HashMap, HashSet};
 use thiserror::Error;
 use uuid::Uuid;
 
@@ -25,7 +26,7 @@ pub struct SceneInstanceReady {
 #[derive(Debug)]
 pub struct InstanceInfo {
     /// Mapping of entities from the scene world to the instance world.
-    pub entity_map: EntityHashMap<Entity, Entity>,
+    pub entity_map: EntityHashMap<Entity>,
 }
 
 /// Unique id identifying a scene instance.
@@ -213,7 +214,7 @@ impl SceneSpawner {
     fn spawn_dynamic_internal(
         world: &mut World,
         id: AssetId<DynamicScene>,
-        entity_map: &mut EntityHashMap<Entity, Entity>,
+        entity_map: &mut EntityHashMap<Entity>,
     ) -> Result<(), SceneSpawnError> {
         world.resource_scope(|world, scenes: Mut<Assets<DynamicScene>>| {
             let scene = scenes

crates/bevy_scene/src/serde.rs

@@ -499,13 +499,13 @@ mod tests {
     use crate::ron;
     use crate::serde::{SceneDeserializer, SceneSerializer};
     use crate::{DynamicScene, DynamicSceneBuilder};
+    use bevy_ecs::entity::EntityHashMap;
     use bevy_ecs::entity::{Entity, EntityMapper, MapEntities};
     use bevy_ecs::prelude::{Component, ReflectComponent, ReflectResource, Resource, World};
     use bevy_ecs::query::{With, Without};
     use bevy_ecs::reflect::{AppTypeRegistry, ReflectMapEntities};
     use bevy_ecs::world::FromWorld;
     use bevy_reflect::{Reflect, ReflectSerialize};
-    use bevy_utils::EntityHashMap;
     use bincode::Options;
     use serde::de::DeserializeSeed;
     use serde::Serialize;

crates/bevy_sprite/src/mesh2d/material.rs

@@ -5,6 +5,7 @@ use bevy_core_pipeline::{
     tonemapping::{DebandDither, Tonemapping},
 };
 use bevy_derive::{Deref, DerefMut};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::{
     prelude::*,
     system::{lifetimeless::SRes, SystemParamItem},
@@ -29,7 +30,7 @@ use bevy_render::{
     Extract, ExtractSchedule, Render, RenderApp, RenderSet,
 };
 use bevy_transform::components::{GlobalTransform, Transform};
-use bevy_utils::{EntityHashMap, FloatOrd, HashMap, HashSet};
+use bevy_utils::{FloatOrd, HashMap, HashSet};
 use std::hash::Hash;
 use std::marker::PhantomData;
 
@@ -180,7 +181,7 @@ where
 }
 
 #[derive(Resource, Deref, DerefMut)]
-pub struct RenderMaterial2dInstances<M: Material2d>(EntityHashMap<Entity, AssetId<M>>);
+pub struct RenderMaterial2dInstances<M: Material2d>(EntityHashMap<AssetId<M>>);
 
 impl<M: Material2d> Default for RenderMaterial2dInstances<M> {
     fn default() -> Self {

crates/bevy_sprite/src/mesh2d/mesh.rs

@@ -3,6 +3,7 @@ use bevy_asset::{load_internal_asset, AssetId, Handle};
 
 use bevy_core_pipeline::core_2d::Transparent2d;
 use bevy_derive::{Deref, DerefMut};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::{
     prelude::*,
     query::ROQueryItem,
@@ -30,7 +31,6 @@ use bevy_render::{
     Extract, ExtractSchedule, Render, RenderApp, RenderSet,
 };
 use bevy_transform::components::GlobalTransform;
-use bevy_utils::EntityHashMap;
 
 use crate::Material2dBindGroupId;
 
@@ -192,7 +192,7 @@ pub struct RenderMesh2dInstance {
 }
 
 #[derive(Default, Resource, Deref, DerefMut)]
-pub struct RenderMesh2dInstances(EntityHashMap<Entity, RenderMesh2dInstance>);
+pub struct RenderMesh2dInstances(EntityHashMap<RenderMesh2dInstance>);
 
 #[derive(Component)]
 pub struct Mesh2d;

crates/bevy_sprite/src/render/mod.rs

@@ -9,6 +9,7 @@ use bevy_core_pipeline::{
     core_2d::Transparent2d,
     tonemapping::{DebandDither, Tonemapping},
 };
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::{
     prelude::*,
     system::{lifetimeless::*, SystemParamItem, SystemState},
@@ -36,7 +37,7 @@ use bevy_render::{
     Extract,
 };
 use bevy_transform::components::GlobalTransform;
-use bevy_utils::{EntityHashMap, FloatOrd, HashMap};
+use bevy_utils::{FloatOrd, HashMap};
 use bytemuck::{Pod, Zeroable};
 use fixedbitset::FixedBitSet;
 
@@ -312,7 +313,7 @@ pub struct ExtractedSprite {
 
 #[derive(Resource, Default)]
 pub struct ExtractedSprites {
-    pub sprites: EntityHashMap<Entity, ExtractedSprite>,
+    pub sprites: EntityHashMap<ExtractedSprite>,
 }
 
 #[derive(Resource, Default)]

crates/bevy_ui/src/layout/mod.rs

@@ -2,6 +2,7 @@ mod convert;
 pub mod debug;
 
 use crate::{ContentSize, DefaultUiCamera, Node, Outline, Style, TargetCamera, UiScale};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::{
     change_detection::{DetectChanges, DetectChangesMut},
     entity::Entity,
@@ -16,7 +17,7 @@ use bevy_log::warn;
 use bevy_math::{UVec2, Vec2};
 use bevy_render::camera::{Camera, NormalizedRenderTarget};
 use bevy_transform::components::Transform;
-use bevy_utils::{default, EntityHashMap, HashMap, HashSet};
+use bevy_utils::{default, HashMap, HashSet};
 use bevy_window::{PrimaryWindow, Window, WindowScaleFactorChanged};
 use std::fmt;
 use taffy::{tree::LayoutTree, Taffy};
@@ -51,14 +52,14 @@ struct RootNodePair {
 
 #[derive(Resource)]
 pub struct UiSurface {
-    entity_to_taffy: EntityHashMap<Entity, taffy::node::Node>,
-    camera_roots: EntityHashMap<Entity, Vec<RootNodePair>>,
+    entity_to_taffy: EntityHashMap<taffy::node::Node>,
+    camera_roots: EntityHashMap<Vec<RootNodePair>>,
     taffy: Taffy,
 }
 
 fn _assert_send_sync_ui_surface_impl_safe() {
     fn _assert_send_sync<T: Send + Sync>() {}
-    _assert_send_sync::<EntityHashMap<Entity, taffy::node::Node>>();
+    _assert_send_sync::<EntityHashMap<taffy::node::Node>>();
     _assert_send_sync::<Taffy>();
     _assert_send_sync::<UiSurface>();
 }

crates/bevy_ui/src/render/mod.rs

@@ -23,6 +23,7 @@ use crate::{
 
 use bevy_app::prelude::*;
 use bevy_asset::{load_internal_asset, AssetEvent, AssetId, Assets, Handle};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::prelude::*;
 use bevy_math::{Mat4, Rect, URect, UVec4, Vec2, Vec3, Vec4Swizzles};
 use bevy_render::{
@@ -41,7 +42,7 @@ use bevy_sprite::TextureAtlasLayout;
 #[cfg(feature = "bevy_text")]
 use bevy_text::{PositionedGlyph, Text, TextLayoutInfo};
 use bevy_transform::components::GlobalTransform;
-use bevy_utils::{EntityHashMap, FloatOrd, HashMap};
+use bevy_utils::{FloatOrd, HashMap};
 use bytemuck::{Pod, Zeroable};
 use std::ops::Range;
 
@@ -147,7 +148,7 @@ pub struct ExtractedUiNode {
 
 #[derive(Resource, Default)]
 pub struct ExtractedUiNodes {
-    pub uinodes: EntityHashMap<Entity, ExtractedUiNode>,
+    pub uinodes: EntityHashMap<ExtractedUiNode>,
 }
 
 pub(crate) fn resolve_border_thickness(value: Val, parent_width: f32, viewport_size: Vec2) -> f32 {

crates/bevy_utils/src/lib.rs

@@ -265,124 +265,6 @@ impl<K: Hash + Eq + PartialEq + Clone, V> PreHashMapExt<K, V> for PreHashMap<K,
     }
 }
 
-/// A [`BuildHasher`] that results in a [`EntityHasher`].
-#[derive(Default, Clone)]
-pub struct EntityHash;
-
-impl BuildHasher for EntityHash {
-    type Hasher = EntityHasher;
-
-    fn build_hasher(&self) -> Self::Hasher {
-        EntityHasher::default()
-    }
-}
-
-/// A very fast hash that is only designed to work on generational indices
-/// like `Entity`. It will panic if attempting to hash a type containing
-/// non-u64 fields.
-///
-/// This is heavily optimized for typical cases, where you have mostly live
-/// entities, and works particularly well for contiguous indices.
-///
-/// If you have an unusual case -- say all your indices are multiples of 256
-/// or most of the entities are dead generations -- then you might want also to
-/// try [`AHasher`] for a slower hash computation but fewer lookup conflicts.
-#[derive(Debug, Default)]
-pub struct EntityHasher {
-    hash: u64,
-}
-
-impl Hasher for EntityHasher {
-    #[inline]
-    fn finish(&self) -> u64 {
-        self.hash
-    }
-
-    fn write(&mut self, _bytes: &[u8]) {
-        panic!("can only hash u64 using EntityHasher");
-    }
-
-    #[inline]
-    fn write_u64(&mut self, bits: u64) {
-        // SwissTable (and thus `hashbrown`) cares about two things from the hash:
-        // - H1: low bits (masked by `2ⁿ-1`) to pick the slot in which to store the item
-        // - H2: high 7 bits are used to SIMD optimize hash collision probing
-        // For more see <https://abseil.io/about/design/swisstables#metadata-layout>
-
-        // This hash function assumes that the entity ids are still well-distributed,
-        // so for H1 leaves the entity id alone in the low bits so that id locality
-        // will also give memory locality for things spawned together.
-        // For H2, take advantage of the fact that while multiplication doesn't
-        // spread entropy to the low bits, it's incredibly good at spreading it
-        // upward, which is exactly where we need it the most.
-
-        // While this does include the generation in the output, it doesn't do so
-        // *usefully*.  H1 won't care until you have over 3 billion entities in
-        // the table, and H2 won't care until something hits generation 33 million.
-        // Thus the comment suggesting that this is best for live entities,
-        // where there won't be generation conflicts where it would matter.
-
-        // The high 32 bits of this are ⅟φ for Fibonacci hashing.  That works
-        // particularly well for hashing for the same reason as described in
-        // <https://extremelearning.com.au/unreasonable-effectiveness-of-quasirandom-sequences/>
-        // It loses no information because it has a modular inverse.
-        // (Specifically, `0x144c_bc89_u32 * 0x9e37_79b9_u32 == 1`.)
-        //
-        // The low 32 bits make that part of the just product a pass-through.
-        const UPPER_PHI: u64 = 0x9e37_79b9_0000_0001;
-
-        // This is `(MAGIC * index + generation) << 32 + index`, in a single instruction.
-        self.hash = bits.wrapping_mul(UPPER_PHI);
-    }
-}
-
-/// A [`HashMap`] pre-configured to use [`EntityHash`] hashing.
-/// Iteration order only depends on the order of insertions and deletions.
-pub type EntityHashMap<K, V> = hashbrown::HashMap<K, V, EntityHash>;
-
-/// A [`HashSet`] pre-configured to use [`EntityHash`] hashing.
-/// Iteration order only depends on the order of insertions and deletions.
-pub type EntityHashSet<T> = hashbrown::HashSet<T, EntityHash>;
-
-/// A specialized hashmap type with Key of [`TypeId`]
-/// Iteration order only depends on the order of insertions and deletions.
-pub type TypeIdMap<V> = hashbrown::HashMap<TypeId, V, NoOpTypeIdHash>;
-
-/// [`BuildHasher`] for [`TypeId`]s.
-#[derive(Default)]
-pub struct NoOpTypeIdHash;
-
-impl BuildHasher for NoOpTypeIdHash {
-    type Hasher = NoOpTypeIdHasher;
-
-    fn build_hasher(&self) -> Self::Hasher {
-        NoOpTypeIdHasher(0)
-    }
-}
-
-#[doc(hidden)]
-pub struct NoOpTypeIdHasher(u64);
-
-// TypeId already contains a high-quality hash, so skip re-hashing that hash.
-impl std::hash::Hasher for NoOpTypeIdHasher {
-    fn finish(&self) -> u64 {
-        self.0
-    }
-
-    fn write(&mut self, bytes: &[u8]) {
-        // This will never be called: TypeId always just calls write_u64 once!
-        // This is a known trick and unlikely to change, but isn't officially guaranteed.
-        // Don't break applications (slower fallback, just check in test):
-        self.0 = bytes.iter().fold(self.0, |hash, b| {
-            hash.rotate_left(8).wrapping_add(*b as u64)
-        });
-    }
-
-    fn write_u64(&mut self, i: u64) {
-        self.0 = i;
-    }
-}
-
 /// A type which calls a function when dropped.
 /// This can be used to ensure that cleanup code is run even in case of a panic.
 ///
@@ -438,6 +320,45 @@ impl<F: FnOnce()> Drop for OnDrop<F> {
     }
 }
 
+/// A specialized hashmap type with Key of [`TypeId`]
+/// Iteration order only depends on the order of insertions and deletions.
+pub type TypeIdMap<V> = hashbrown::HashMap<TypeId, V, NoOpTypeIdHash>;
+
+/// [`BuildHasher`] for [`TypeId`]s.
+#[derive(Default)]
+pub struct NoOpTypeIdHash;
+
+impl BuildHasher for NoOpTypeIdHash {
+    type Hasher = NoOpTypeIdHasher;
+
+    fn build_hasher(&self) -> Self::Hasher {
+        NoOpTypeIdHasher(0)
+    }
+}
+#[doc(hidden)]
+#[derive(Default)]
+pub struct NoOpTypeIdHasher(pub u64);
+
+// TypeId already contains a high-quality hash, so skip re-hashing that hash.
+impl std::hash::Hasher for NoOpTypeIdHasher {
+    fn finish(&self) -> u64 {
+        self.0
+    }
+
+    fn write(&mut self, bytes: &[u8]) {
+        // This will never be called: TypeId always just calls write_u64 once!
+        // This is a known trick and unlikely to change, but isn't officially guaranteed.
+        // Don't break applications (slower fallback, just check in test):
+        self.0 = bytes.iter().fold(self.0, |hash, b| {
+            hash.rotate_left(8).wrapping_add(*b as u64)
+        });
+    }
+
+    fn write_u64(&mut self, i: u64) {
+        self.0 = i;
+    }
+}
+
 /// Calls the [`tracing::info!`] macro on a value.
 pub fn info<T: Debug>(data: T) {
     tracing::info!("{:?}", data);
@@ -478,7 +399,6 @@ mod tests {
     use static_assertions::assert_impl_all;
 
     // Check that the HashMaps are Clone if the key/values are Clone
-    assert_impl_all!(EntityHashMap::<u64, usize>: Clone);
     assert_impl_all!(PreHashMap::<u64, usize>: Clone);
 
     #[test]

crates/bevy_winit/src/accessibility.rs

@@ -15,6 +15,7 @@ use bevy_a11y::{
 use bevy_a11y::{ActionRequest as ActionRequestWrapper, ManageAccessibilityUpdates};
 use bevy_app::{App, Plugin, PostUpdate};
 use bevy_derive::{Deref, DerefMut};
+use bevy_ecs::entity::EntityHashMap;
 use bevy_ecs::{
     prelude::{DetectChanges, Entity, EventReader, EventWriter},
     query::With,
@@ -22,16 +23,15 @@ use bevy_ecs::{
     system::{NonSend, NonSendMut, Query, Res, ResMut, Resource},
 };
 use bevy_hierarchy::{Children, Parent};
-use bevy_utils::EntityHashMap;
 use bevy_window::{PrimaryWindow, Window, WindowClosed};
 
 /// Maps window entities to their `AccessKit` [`Adapter`]s.
 #[derive(Default, Deref, DerefMut)]
-pub struct AccessKitAdapters(pub EntityHashMap<Entity, Adapter>);
+pub struct AccessKitAdapters(pub EntityHashMap<Adapter>);
 
 /// Maps window entities to their respective [`WinitActionHandler`]s.
 #[derive(Resource, Default, Deref, DerefMut)]
-pub struct WinitActionHandlers(pub EntityHashMap<Entity, WinitActionHandler>);
+pub struct WinitActionHandlers(pub EntityHashMap<WinitActionHandler>);
 
 /// Forwards `AccessKit` [`ActionRequest`]s from winit to an event channel.
 #[derive(Clone, Default, Deref, DerefMut)]

crates/bevy_winit/src/winit_windows.rs

@@ -5,7 +5,8 @@ use bevy_a11y::{
 };
 use bevy_ecs::entity::Entity;
 
-use bevy_utils::{tracing::warn, EntityHashMap, HashMap};
+use bevy_ecs::entity::EntityHashMap;
+use bevy_utils::{tracing::warn, HashMap};
 use bevy_window::{CursorGrabMode, Window, WindowMode, WindowPosition, WindowResolution};
 
 use winit::{
@@ -25,7 +26,7 @@ pub struct WinitWindows {
     /// Stores [`winit`] windows by window identifier.
     pub windows: HashMap<winit::window::WindowId, winit::window::Window>,
     /// Maps entities to `winit` window identifiers.
-    pub entity_to_winit: EntityHashMap<Entity, winit::window::WindowId>,
+    pub entity_to_winit: EntityHashMap<winit::window::WindowId>,
     /// Maps `winit` window identifiers to entities.
     pub winit_to_entity: HashMap<winit::window::WindowId, Entity>,
     // Many `winit` window functions (e.g. `set_window_icon`) can only be called on the main thread.