From 9d48785f485673b7b0466a041960e29107bb8213 Mon Sep 17 00:00:00 2001
From: Carter Anderson <mcanders1@gmail.com>
Date: Sat, 29 May 2021 15:35:08 -0700
Subject: [PATCH 1/6] Rename SystemState to SystemMeta. Add new SystemState

---
 crates/bevy_ecs/macros/src/lib.rs             |  37 +--
 .../{into_system.rs => function_system.rs}    | 127 ++++++++--
 crates/bevy_ecs/src/system/mod.rs             |  56 ++++-
 crates/bevy_ecs/src/system/system_param.rs    | 221 +++++++++++-------
 4 files changed, 314 insertions(+), 127 deletions(-)
 rename crates/bevy_ecs/src/system/{into_system.rs => function_system.rs} (66%)

diff --git a/crates/bevy_ecs/macros/src/lib.rs b/crates/bevy_ecs/macros/src/lib.rs
index 1d4cb94c2a7c0..de79099c1cda0 100644
--- a/crates/bevy_ecs/macros/src/lib.rs
+++ b/crates/bevy_ecs/macros/src/lib.rs
@@ -221,40 +221,45 @@ pub fn impl_query_set(_input: TokenStream) -> TokenStream {
                 type Fetch = QuerySetState<(#(QueryState<#query, #filter>,)*)>;
             }
 
-            // SAFE: Relevant query ComponentId and ArchetypeComponentId access is applied to SystemState. If any QueryState conflicts
+            // SAFE: All Queries are constrained to ReadOnlyFetch, so World is only read
+            unsafe impl<#(#query: WorldQuery + 'static,)* #(#filter: WorldQuery + 'static,)*> ReadOnlySystemParamFetch for QuerySetState<(#(QueryState<#query, #filter>,)*)>
+            where #(#query::Fetch: ReadOnlyFetch,)* #(#filter::Fetch: FilterFetch,)*
+            { }
+
+            // SAFE: Relevant query ComponentId and ArchetypeComponentId access is applied to SystemMeta. If any QueryState conflicts
             // with any prior access, a panic will occur.
             unsafe impl<#(#query: WorldQuery + 'static,)* #(#filter: WorldQuery + 'static,)*> SystemParamState for QuerySetState<(#(QueryState<#query, #filter>,)*)>
                 where #(#filter::Fetch: FilterFetch,)*
             {
                 type Config = ();
-                fn init(world: &mut World, system_state: &mut SystemState, config: Self::Config) -> Self {
+                fn init(world: &mut World, system_meta: &mut SystemMeta, config: Self::Config) -> Self {
                     #(
                         let mut #query = QueryState::<#query, #filter>::new(world);
                         assert_component_access_compatibility(
-                            &system_state.name,
+                            &system_meta.name,
                             std::any::type_name::<#query>(),
                             std::any::type_name::<#filter>(),
-                            &system_state.component_access_set,
+                            &system_meta.component_access_set,
                             &#query.component_access,
                             world,
                         );
                     )*
                     #(
-                        system_state
+                        system_meta
                             .component_access_set
                             .add(#query.component_access.clone());
-                        system_state
+                        system_meta
                             .archetype_component_access
                             .extend(&#query.archetype_component_access);
                     )*
                     QuerySetState((#(#query,)*))
                 }
 
-                fn new_archetype(&mut self, archetype: &Archetype, system_state: &mut SystemState) {
+                fn new_archetype(&mut self, archetype: &Archetype, system_meta: &mut SystemMeta) {
                     let (#(#query,)*) = &mut self.0;
                     #(
                         #query.new_archetype(archetype);
-                        system_state
+                        system_meta
                             .archetype_component_access
                             .extend(&#query.archetype_component_access);
                     )*
@@ -271,12 +276,12 @@ pub fn impl_query_set(_input: TokenStream) -> TokenStream {
                 #[inline]
                 unsafe fn get_param(
                     state: &'a mut Self,
-                    system_state: &'a SystemState,
+                    system_meta: &'a SystemMeta,
                     world: &'a World,
                     change_tick: u32,
                 ) -> Self::Item {
                     let (#(#query,)*) = &state.0;
-                    QuerySet((#(Query::new(world, #query, system_state.last_change_tick, change_tick),)*))
+                    QuerySet((#(Query::new(world, #query, system_meta.last_change_tick, change_tick),)*))
                 }
             }
 
@@ -388,15 +393,15 @@ pub fn derive_system_param(input: TokenStream) -> TokenStream {
 
         unsafe impl<TSystemParamState: #path::system::SystemParamState, #punctuated_generics> #path::system::SystemParamState for #fetch_struct_name<TSystemParamState, #punctuated_generic_idents> {
             type Config = TSystemParamState::Config;
-            fn init(world: &mut #path::world::World, system_state: &mut #path::system::SystemState, config: Self::Config) -> Self {
+            fn init(world: &mut #path::world::World, system_meta: &mut #path::system::SystemMeta, config: Self::Config) -> Self {
                 Self {
-                    state: TSystemParamState::init(world, system_state, config),
+                    state: TSystemParamState::init(world, system_meta, config),
                     marker: std::marker::PhantomData,
                 }
             }
 
-            fn new_archetype(&mut self, archetype: &#path::archetype::Archetype, system_state: &mut #path::system::SystemState) {
-                self.state.new_archetype(archetype, system_state)
+            fn new_archetype(&mut self, archetype: &#path::archetype::Archetype, system_meta: &mut #path::system::SystemMeta) {
+                self.state.new_archetype(archetype, system_meta)
             }
 
             fn default_config() -> TSystemParamState::Config {
@@ -412,12 +417,12 @@ pub fn derive_system_param(input: TokenStream) -> TokenStream {
             type Item = #struct_name#ty_generics;
             unsafe fn get_param(
                 state: &'a mut Self,
-                system_state: &'a #path::system::SystemState,
+                system_meta: &'a #path::system::SystemMeta,
                 world: &'a #path::world::World,
                 change_tick: u32,
             ) -> Self::Item {
                 #struct_name {
-                    #(#fields: <<#field_types as SystemParam>::Fetch as #path::system::SystemParamFetch>::get_param(&mut state.state.#field_indices, system_state, world, change_tick),)*
+                    #(#fields: <<#field_types as SystemParam>::Fetch as #path::system::SystemParamFetch>::get_param(&mut state.state.#field_indices, system_meta, world, change_tick),)*
                     #(#ignored_fields: <#ignored_field_types>::default(),)*
                 }
             }
diff --git a/crates/bevy_ecs/src/system/into_system.rs b/crates/bevy_ecs/src/system/function_system.rs
similarity index 66%
rename from crates/bevy_ecs/src/system/into_system.rs
rename to crates/bevy_ecs/src/system/function_system.rs
index 97f3e0f62f0f2..4c3bcf885f136 100644
--- a/crates/bevy_ecs/src/system/into_system.rs
+++ b/crates/bevy_ecs/src/system/function_system.rs
@@ -3,26 +3,27 @@ use crate::{
     component::ComponentId,
     query::{Access, FilteredAccessSet},
     system::{
-        check_system_change_tick, System, SystemId, SystemParam, SystemParamFetch, SystemParamState,
+        check_system_change_tick, ReadOnlySystemParamFetch, System, SystemId, SystemParam,
+        SystemParamFetch, SystemParamState,
     },
     world::World,
 };
 use bevy_ecs_macros::all_tuples;
 use std::{borrow::Cow, marker::PhantomData};
 
-/// The state of a [`System`].
-pub struct SystemState {
+/// The metadata of a [`System`].
+pub struct SystemMeta {
     pub(crate) id: SystemId,
     pub(crate) name: Cow<'static, str>,
     pub(crate) component_access_set: FilteredAccessSet<ComponentId>,
     pub(crate) archetype_component_access: Access<ArchetypeComponentId>,
-    // NOTE: this must be kept private. making a SystemState non-send is irreversible to prevent
+    // NOTE: this must be kept private. making a SystemMeta non-send is irreversible to prevent
     // SystemParams from overriding each other
     is_send: bool,
     pub(crate) last_change_tick: u32,
 }
 
-impl SystemState {
+impl SystemMeta {
     fn new<T>() -> Self {
         Self {
             name: std::any::type_name::<T>().into(),
@@ -49,6 +50,86 @@ impl SystemState {
     }
 }
 
+// TODO: Actually use this in FunctionSystem. We should probably only do this once Systems are constructed using a World reference
+// (to avoid the need for unwrapping to retrieve SystemMeta)
+/// Holds on to persistent state required to drive [`SystemParam`] for a [`System`].  
+pub struct SystemState<Param: SystemParam> {
+    meta: SystemMeta,
+    param_state: <Param as SystemParam>::Fetch,
+    change_tick: u32,
+}
+
+impl<Param: SystemParam> SystemState<Param> {
+    pub fn new(world: &mut World) -> Self {
+        let config = <Param::Fetch as SystemParamState>::default_config();
+        Self::with_config(world, config)
+    }
+
+    pub fn with_config(
+        world: &mut World,
+        config: <Param::Fetch as SystemParamState>::Config,
+    ) -> Self {
+        let mut meta = SystemMeta::new::<Param>();
+        let param_state = <Param::Fetch as SystemParamState>::init(world, &mut meta, config);
+        Self {
+            meta,
+            param_state,
+            change_tick: 0,
+        }
+    }
+
+    #[inline]
+    pub fn meta(&self) -> &SystemMeta {
+        &self.meta
+    }
+
+    /// Retrieve the [`SystemParam`] values. This can only be called when all parameters are read-only.
+    pub fn get<'a>(&'a mut self, world: &'a World) -> <Param::Fetch as SystemParamFetch<'a>>::Item
+    where
+        Param::Fetch: ReadOnlySystemParamFetch,
+    {
+        // SAFE: Param is read-only and doesn't allow mutable access to World
+        unsafe { self.get_unchecked(world) }
+    }
+
+    /// Retrieve the mutable [`SystemParam`] values.
+    pub fn get_mut<'a>(
+        &'a mut self,
+        world: &'a mut World,
+    ) -> <Param::Fetch as SystemParamFetch<'a>>::Item {
+        // SAFE: World is uniquely borrowed
+        unsafe { self.get_unchecked(world) }
+    }
+
+    /// Applies all state queued up for [`SystemParam`] values. For example, this will apply commands queued up
+    /// by a [`Commands`](`super::Commands`) parameter to the given [`World`].
+    /// This function should be called manually after the values returned by [`SystemState::get`] and [`SystemState::get_mut`]  
+    /// are finished being used.
+    pub fn apply(&mut self, world: &mut World) {
+        self.param_state.apply(world);
+    }
+
+    /// Retrieve the [`SystemParam`] values.
+    ///
+    /// # Safety
+    /// This call might access any of the input parameters in a way that violates Rust's mutability rules. Make sure the data
+    /// access is safe in the context of global [`World`] access.
+    #[inline]
+    pub unsafe fn get_unchecked<'a>(
+        &'a mut self,
+        world: &'a World,
+    ) -> <Param::Fetch as SystemParamFetch<'a>>::Item {
+        let change_tick = world.increment_change_tick();
+        self.change_tick = change_tick;
+        <Param::Fetch as SystemParamFetch>::get_param(
+            &mut self.param_state,
+            &self.meta,
+            world,
+            change_tick,
+        )
+    }
+}
+
 /// Conversion trait to turn something into a [`System`].
 ///
 /// Use this to get a system from a function. Also note that every system implements this trait as
@@ -116,7 +197,7 @@ where
 {
     func: F,
     param_state: Option<Param::Fetch>,
-    system_state: SystemState,
+    system_meta: SystemMeta,
     config: Option<<Param::Fetch as SystemParamState>::Config>,
     // NOTE: PhantomData<fn()-> T> gives this safe Send/Sync impls
     #[allow(clippy::type_complexity)]
@@ -161,7 +242,7 @@ where
             func: self,
             param_state: None,
             config: Some(<Param::Fetch as SystemParamState>::default_config()),
-            system_state: SystemState::new::<F>(),
+            system_meta: SystemMeta::new::<F>(),
             marker: PhantomData,
         }
     }
@@ -180,33 +261,33 @@ where
 
     #[inline]
     fn name(&self) -> Cow<'static, str> {
-        self.system_state.name.clone()
+        self.system_meta.name.clone()
     }
 
     #[inline]
     fn id(&self) -> SystemId {
-        self.system_state.id
+        self.system_meta.id
     }
 
     #[inline]
     fn new_archetype(&mut self, archetype: &Archetype) {
         let param_state = self.param_state.as_mut().unwrap();
-        param_state.new_archetype(archetype, &mut self.system_state);
+        param_state.new_archetype(archetype, &mut self.system_meta);
     }
 
     #[inline]
     fn component_access(&self) -> &Access<ComponentId> {
-        &self.system_state.component_access_set.combined_access()
+        &self.system_meta.component_access_set.combined_access()
     }
 
     #[inline]
     fn archetype_component_access(&self) -> &Access<ArchetypeComponentId> {
-        &self.system_state.archetype_component_access
+        &self.system_meta.archetype_component_access
     }
 
     #[inline]
     fn is_send(&self) -> bool {
-        self.system_state.is_send
+        self.system_meta.is_send
     }
 
     #[inline]
@@ -215,11 +296,11 @@ where
         let out = self.func.run(
             input,
             self.param_state.as_mut().unwrap(),
-            &self.system_state,
+            &self.system_meta,
             world,
             change_tick,
         );
-        self.system_state.last_change_tick = change_tick;
+        self.system_meta.last_change_tick = change_tick;
         out
     }
 
@@ -233,7 +314,7 @@ where
     fn initialize(&mut self, world: &mut World) {
         self.param_state = Some(<Param::Fetch as SystemParamState>::init(
             world,
-            &mut self.system_state,
+            &mut self.system_meta,
             self.config.take().unwrap(),
         ));
     }
@@ -241,9 +322,9 @@ where
     #[inline]
     fn check_change_tick(&mut self, change_tick: u32) {
         check_system_change_tick(
-            &mut self.system_state.last_change_tick,
+            &mut self.system_meta.last_change_tick,
             change_tick,
-            self.system_state.name.as_ref(),
+            self.system_meta.name.as_ref(),
         );
     }
 }
@@ -254,7 +335,7 @@ pub trait SystemParamFunction<In, Out, Param: SystemParam, Marker>: Send + Sync
         &mut self,
         input: In,
         state: &mut Param::Fetch,
-        system_state: &SystemState,
+        system_meta: &SystemMeta,
         world: &World,
         change_tick: u32,
     ) -> Out;
@@ -270,9 +351,9 @@ macro_rules! impl_system_function {
                 FnMut($(<<$param as SystemParam>::Fetch as SystemParamFetch>::Item),*) -> Out + Send + Sync + 'static, Out: 'static
         {
             #[inline]
-            fn run(&mut self, _input: (), state: &mut <($($param,)*) as SystemParam>::Fetch, system_state: &SystemState, world: &World, change_tick: u32) -> Out {
+            fn run(&mut self, _input: (), state: &mut <($($param,)*) as SystemParam>::Fetch, system_meta: &SystemMeta, world: &World, change_tick: u32) -> Out {
                 unsafe {
-                    let ($($param,)*) = <<($($param,)*) as SystemParam>::Fetch as SystemParamFetch>::get_param(state, system_state, world, change_tick);
+                    let ($($param,)*) = <<($($param,)*) as SystemParam>::Fetch as SystemParamFetch>::get_param(state, system_meta, world, change_tick);
                     self($($param),*)
                 }
             }
@@ -286,9 +367,9 @@ macro_rules! impl_system_function {
                 FnMut(In<Input>, $(<<$param as SystemParam>::Fetch as SystemParamFetch>::Item),*) -> Out + Send + Sync + 'static, Out: 'static
         {
             #[inline]
-            fn run(&mut self, input: Input, state: &mut <($($param,)*) as SystemParam>::Fetch, system_state: &SystemState, world: &World, change_tick: u32) -> Out {
+            fn run(&mut self, input: Input, state: &mut <($($param,)*) as SystemParam>::Fetch, system_meta: &SystemMeta, world: &World, change_tick: u32) -> Out {
                 unsafe {
-                    let ($($param,)*) = <<($($param,)*) as SystemParam>::Fetch as SystemParamFetch>::get_param(state, system_state, world, change_tick);
+                    let ($($param,)*) = <<($($param,)*) as SystemParam>::Fetch as SystemParamFetch>::get_param(state, system_meta, world, change_tick);
                     self(In(input), $($param),*)
                 }
             }
diff --git a/crates/bevy_ecs/src/system/mod.rs b/crates/bevy_ecs/src/system/mod.rs
index b10ec03c6506e..6ba08a8a71c5b 100644
--- a/crates/bevy_ecs/src/system/mod.rs
+++ b/crates/bevy_ecs/src/system/mod.rs
@@ -1,6 +1,6 @@
 mod commands;
 mod exclusive_system;
-mod into_system;
+mod function_system;
 mod query;
 #[allow(clippy::module_inception)]
 mod system;
@@ -9,7 +9,7 @@ mod system_param;
 
 pub use commands::*;
 pub use exclusive_system::*;
-pub use into_system::*;
+pub use function_system::*;
 pub use query::*;
 pub use system::*;
 pub use system_chaining::*;
@@ -28,7 +28,7 @@ mod tests {
         schedule::{Schedule, Stage, SystemStage},
         system::{
             IntoExclusiveSystem, IntoSystem, Local, Query, QuerySet, RemovedComponents, Res,
-            ResMut, System,
+            ResMut, System, SystemState,
         },
         world::{FromWorld, World},
     };
@@ -485,4 +485,54 @@ mod tests {
         x.initialize(&mut world);
         y.initialize(&mut world);
     }
+
+    #[test]
+    fn read_system_param() {
+        #[derive(Eq, PartialEq, Debug)]
+        struct A(usize);
+
+        #[derive(Eq, PartialEq, Debug)]
+        struct B(usize);
+
+        let mut world = World::default();
+        world.insert_resource(A(42));
+        world.spawn().insert(B(7));
+
+        let mut system_state: SystemState<(Res<A>, Query<&B>, QuerySet<(Query<&C>, Query<&D>)>)> =
+            SystemState::new(&mut world);
+        let (a, query, _) = system_state.get(&world);
+        assert_eq!(*a, A(42), "returned resource matches initial value");
+        assert_eq!(
+            *query.single().unwrap(),
+            B(7),
+            "returned component matches initial value"
+        );
+    }
+
+    #[test]
+    fn write_system_param() {
+        #[derive(Eq, PartialEq, Debug)]
+        struct A(usize);
+
+        #[derive(Eq, PartialEq, Debug)]
+        struct B(usize);
+
+        let mut world = World::default();
+        world.insert_resource(A(42));
+        world.spawn().insert(B(7));
+
+        let mut system_state: SystemState<(ResMut<A>, Query<&mut B>)> =
+            SystemState::new(&mut world);
+
+        // The following line shouldn't compile because the parameters used are not ReadOnlySystemParam
+        // let (a, query) = system_state.get(&world);
+
+        let (a, mut query) = system_state.get_mut(&mut world);
+        assert_eq!(*a, A(42), "returned resource matches initial value");
+        assert_eq!(
+            *query.single_mut().unwrap(),
+            B(7),
+            "returned component matches initial value"
+        );
+    }
 }
diff --git a/crates/bevy_ecs/src/system/system_param.rs b/crates/bevy_ecs/src/system/system_param.rs
index 07a8499971396..9cd46476593bc 100644
--- a/crates/bevy_ecs/src/system/system_param.rs
+++ b/crates/bevy_ecs/src/system/system_param.rs
@@ -5,8 +5,10 @@ use crate::{
     change_detection::Ticks,
     component::{Component, ComponentId, ComponentTicks, Components},
     entity::{Entities, Entity},
-    query::{FilterFetch, FilteredAccess, FilteredAccessSet, QueryState, WorldQuery},
-    system::{CommandQueue, Commands, Query, SystemState},
+    query::{
+        FilterFetch, FilteredAccess, FilteredAccessSet, QueryState, ReadOnlyFetch, WorldQuery,
+    },
+    system::{CommandQueue, Commands, Query, SystemMeta},
     world::{FromWorld, World},
 };
 pub use bevy_ecs_macros::SystemParam;
@@ -46,7 +48,7 @@ pub trait SystemParam: Sized {
 ///
 /// # Safety
 ///
-/// It is the implementor's responsibility to ensure `system_state` is populated with the _exact_
+/// It is the implementor's responsibility to ensure `system_meta` is populated with the _exact_
 /// [`World`] access used by the `SystemParamState` (and associated [`SystemParamFetch`]).
 /// Additionally, it is the implementor's responsibility to ensure there is no
 /// conflicting access across all SystemParams.
@@ -64,14 +66,20 @@ pub unsafe trait SystemParamState: Send + Sync + 'static {
     /// See [`FunctionSystem::config`](super::FunctionSystem::config)
     /// for more information and examples.
     type Config: Send + Sync;
-    fn init(world: &mut World, system_state: &mut SystemState, config: Self::Config) -> Self;
+    fn init(world: &mut World, system_meta: &mut SystemMeta, config: Self::Config) -> Self;
     #[inline]
-    fn new_archetype(&mut self, _archetype: &Archetype, _system_state: &mut SystemState) {}
+    fn new_archetype(&mut self, _archetype: &Archetype, _system_meta: &mut SystemMeta) {}
     #[inline]
     fn apply(&mut self, _world: &mut World) {}
     fn default_config() -> Self::Config;
 }
 
+/// A [`SystemParamFetch`] that only reads a given [`World`].
+///
+/// # Safety
+/// This must only be implemented for [`SystemParamFetch`] impls that exclusively read the World passed in to [`SystemParamFetch::get_param`]
+pub unsafe trait ReadOnlySystemParamFetch {}
+
 pub trait SystemParamFetch<'a>: SystemParamState {
     type Item;
     /// # Safety
@@ -80,14 +88,12 @@ pub trait SystemParamFetch<'a>: SystemParamState {
     /// access is safe in the context of the system scheduler.
     unsafe fn get_param(
         state: &'a mut Self,
-        system_state: &'a SystemState,
+        system_meta: &'a SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item;
 }
 
-pub struct QueryFetch<Q, F>(PhantomData<(Q, F)>);
-
 impl<'a, Q: WorldQuery + 'static, F: WorldQuery + 'static> SystemParam for Query<'a, Q, F>
 where
     F::Fetch: FilterFetch,
@@ -95,7 +101,15 @@ where
     type Fetch = QueryState<Q, F>;
 }
 
-// SAFE: Relevant query ComponentId and ArchetypeComponentId access is applied to SystemState. If
+// SAFE: QueryState is constrained to read-only fetches, so it only reads World.
+unsafe impl<Q: WorldQuery, F: WorldQuery> ReadOnlySystemParamFetch for QueryState<Q, F>
+where
+    Q::Fetch: ReadOnlyFetch,
+    F::Fetch: FilterFetch,
+{
+}
+
+// SAFE: Relevant query ComponentId and ArchetypeComponentId access is applied to SystemMeta. If
 // this QueryState conflicts with any prior access, a panic will occur.
 unsafe impl<Q: WorldQuery + 'static, F: WorldQuery + 'static> SystemParamState for QueryState<Q, F>
 where
@@ -103,28 +117,28 @@ where
 {
     type Config = ();
 
-    fn init(world: &mut World, system_state: &mut SystemState, _config: Self::Config) -> Self {
+    fn init(world: &mut World, system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
         let state = QueryState::new(world);
         assert_component_access_compatibility(
-            &system_state.name,
+            &system_meta.name,
             std::any::type_name::<Q>(),
             std::any::type_name::<F>(),
-            &system_state.component_access_set,
+            &system_meta.component_access_set,
             &state.component_access,
             world,
         );
-        system_state
+        system_meta
             .component_access_set
             .add(state.component_access.clone());
-        system_state
+        system_meta
             .archetype_component_access
             .extend(&state.archetype_component_access);
         state
     }
 
-    fn new_archetype(&mut self, archetype: &Archetype, system_state: &mut SystemState) {
+    fn new_archetype(&mut self, archetype: &Archetype, system_meta: &mut SystemMeta) {
         self.new_archetype(archetype);
-        system_state
+        system_meta
             .archetype_component_access
             .extend(&self.archetype_component_access);
     }
@@ -141,11 +155,11 @@ where
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_state: &'a SystemState,
+        system_meta: &'a SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
-        Query::new(world, state, system_state.last_change_tick, change_tick)
+        Query::new(world, state, system_meta.last_change_tick, change_tick)
     }
 }
 
@@ -189,6 +203,9 @@ pub struct Res<'w, T: Component> {
     change_tick: u32,
 }
 
+// SAFE: Res only reads a single World resource
+unsafe impl<T: Component> ReadOnlySystemParamFetch for ResState<T> {}
+
 impl<'w, T: Component> Debug for Res<'w, T>
 where
     T: Debug,
@@ -238,18 +255,18 @@ impl<'a, T: Component> SystemParam for Res<'a, T> {
     type Fetch = ResState<T>;
 }
 
-// SAFE: Res ComponentId and ArchetypeComponentId access is applied to SystemState. If this Res
+// SAFE: Res ComponentId and ArchetypeComponentId access is applied to SystemMeta. If this Res
 // conflicts with any prior access, a panic will occur.
 unsafe impl<T: Component> SystemParamState for ResState<T> {
     type Config = ();
 
-    fn init(world: &mut World, system_state: &mut SystemState, _config: Self::Config) -> Self {
+    fn init(world: &mut World, system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
         let component_id = world.initialize_resource::<T>();
-        let combined_access = system_state.component_access_set.combined_access_mut();
+        let combined_access = system_meta.component_access_set.combined_access_mut();
         if combined_access.has_write(component_id) {
             panic!(
                 "Res<{}> in system {} conflicts with a previous ResMut<{0}> access. Allowing this would break Rust's mutability rules. Consider removing the duplicate access.",
-                std::any::type_name::<T>(), system_state.name);
+                std::any::type_name::<T>(), system_meta.name);
         }
         combined_access.add_read(component_id);
 
@@ -257,7 +274,7 @@ unsafe impl<T: Component> SystemParamState for ResState<T> {
         let archetype_component_id = resource_archetype
             .get_archetype_component_id(component_id)
             .unwrap();
-        system_state
+        system_meta
             .archetype_component_access
             .add_read(archetype_component_id);
         Self {
@@ -275,7 +292,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for ResState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_state: &'a SystemState,
+        system_meta: &'a SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -284,14 +301,14 @@ impl<'a, T: Component> SystemParamFetch<'a> for ResState<T> {
             .unwrap_or_else(|| {
                 panic!(
                     "Resource requested by {} does not exist: {}",
-                    system_state.name,
+                    system_meta.name,
                     std::any::type_name::<T>()
                 )
             });
         Res {
             value: &*column.get_data_ptr().cast::<T>().as_ptr(),
             ticks: column.get_ticks_unchecked(0),
-            last_change_tick: system_state.last_change_tick,
+            last_change_tick: system_meta.last_change_tick,
             change_tick,
         }
     }
@@ -304,11 +321,14 @@ impl<'a, T: Component> SystemParam for Option<Res<'a, T>> {
     type Fetch = OptionResState<T>;
 }
 
+// SAFE: Only reads a single World resource
+unsafe impl<T: Component> ReadOnlySystemParamFetch for OptionResState<T> {}
+
 unsafe impl<T: Component> SystemParamState for OptionResState<T> {
     type Config = ();
 
-    fn init(world: &mut World, system_state: &mut SystemState, _config: Self::Config) -> Self {
-        Self(ResState::init(world, system_state, ()))
+    fn init(world: &mut World, system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
+        Self(ResState::init(world, system_meta, ()))
     }
 
     fn default_config() {}
@@ -320,7 +340,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for OptionResState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_state: &'a SystemState,
+        system_meta: &'a SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -329,7 +349,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for OptionResState<T> {
             .map(|column| Res {
                 value: &*column.get_data_ptr().cast::<T>().as_ptr(),
                 ticks: column.get_ticks_unchecked(0),
-                last_change_tick: system_state.last_change_tick,
+                last_change_tick: system_meta.last_change_tick,
                 change_tick,
             })
     }
@@ -345,22 +365,22 @@ impl<'a, T: Component> SystemParam for ResMut<'a, T> {
     type Fetch = ResMutState<T>;
 }
 
-// SAFE: Res ComponentId and ArchetypeComponentId access is applied to SystemState. If this Res
+// SAFE: Res ComponentId and ArchetypeComponentId access is applied to SystemMeta. If this Res
 // conflicts with any prior access, a panic will occur.
 unsafe impl<T: Component> SystemParamState for ResMutState<T> {
     type Config = ();
 
-    fn init(world: &mut World, system_state: &mut SystemState, _config: Self::Config) -> Self {
+    fn init(world: &mut World, system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
         let component_id = world.initialize_resource::<T>();
-        let combined_access = system_state.component_access_set.combined_access_mut();
+        let combined_access = system_meta.component_access_set.combined_access_mut();
         if combined_access.has_write(component_id) {
             panic!(
                 "ResMut<{}> in system {} conflicts with a previous ResMut<{0}> access. Allowing this would break Rust's mutability rules. Consider removing the duplicate access.",
-                std::any::type_name::<T>(), system_state.name);
+                std::any::type_name::<T>(), system_meta.name);
         } else if combined_access.has_read(component_id) {
             panic!(
                 "ResMut<{}> in system {} conflicts with a previous Res<{0}> access. Allowing this would break Rust's mutability rules. Consider removing the duplicate access.",
-                std::any::type_name::<T>(), system_state.name);
+                std::any::type_name::<T>(), system_meta.name);
         }
         combined_access.add_write(component_id);
 
@@ -368,7 +388,7 @@ unsafe impl<T: Component> SystemParamState for ResMutState<T> {
         let archetype_component_id = resource_archetype
             .get_archetype_component_id(component_id)
             .unwrap();
-        system_state
+        system_meta
             .archetype_component_access
             .add_write(archetype_component_id);
         Self {
@@ -386,7 +406,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for ResMutState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_state: &'a SystemState,
+        system_meta: &'a SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -395,7 +415,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for ResMutState<T> {
             .unwrap_or_else(|| {
                 panic!(
                     "Resource requested by {} does not exist: {}",
-                    system_state.name,
+                    system_meta.name,
                     std::any::type_name::<T>()
                 )
             });
@@ -403,7 +423,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for ResMutState<T> {
             value: value.value,
             ticks: Ticks {
                 component_ticks: value.ticks.component_ticks,
-                last_change_tick: system_state.last_change_tick,
+                last_change_tick: system_meta.last_change_tick,
                 change_tick,
             },
         }
@@ -420,8 +440,8 @@ impl<'a, T: Component> SystemParam for Option<ResMut<'a, T>> {
 unsafe impl<T: Component> SystemParamState for OptionResMutState<T> {
     type Config = ();
 
-    fn init(world: &mut World, system_state: &mut SystemState, _config: Self::Config) -> Self {
-        Self(ResMutState::init(world, system_state, ()))
+    fn init(world: &mut World, system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
+        Self(ResMutState::init(world, system_meta, ()))
     }
 
     fn default_config() {}
@@ -433,7 +453,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for OptionResMutState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_state: &'a SystemState,
+        system_meta: &'a SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -443,7 +463,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for OptionResMutState<T> {
                 value: value.value,
                 ticks: Ticks {
                     component_ticks: value.ticks.component_ticks,
-                    last_change_tick: system_state.last_change_tick,
+                    last_change_tick: system_meta.last_change_tick,
                     change_tick,
                 },
             })
@@ -454,11 +474,14 @@ impl<'a> SystemParam for Commands<'a> {
     type Fetch = CommandQueue;
 }
 
+// SAFE: Commands only accesses internal state
+unsafe impl ReadOnlySystemParamFetch for CommandQueue {}
+
 // SAFE: only local state is accessed
 unsafe impl SystemParamState for CommandQueue {
     type Config = ();
 
-    fn init(_world: &mut World, _system_state: &mut SystemState, _config: Self::Config) -> Self {
+    fn init(_world: &mut World, _system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
         Default::default()
     }
 
@@ -475,7 +498,7 @@ impl<'a> SystemParamFetch<'a> for CommandQueue {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        _system_state: &'a SystemState,
+        _system_meta: &'a SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -511,6 +534,9 @@ impl<'a> SystemParamFetch<'a> for CommandQueue {
 /// ```
 pub struct Local<'a, T: Component>(&'a mut T);
 
+// SAFE: Local only accesses internal state
+unsafe impl<T: Component> ReadOnlySystemParamFetch for LocalState<T> {}
+
 impl<'a, T: Component> Debug for Local<'a, T>
 where
     T: Debug,
@@ -547,7 +573,7 @@ impl<'a, T: Component + FromWorld> SystemParam for Local<'a, T> {
 unsafe impl<T: Component + FromWorld> SystemParamState for LocalState<T> {
     type Config = Option<T>;
 
-    fn init(world: &mut World, _system_state: &mut SystemState, config: Self::Config) -> Self {
+    fn init(world: &mut World, _system_meta: &mut SystemMeta, config: Self::Config) -> Self {
         Self(config.unwrap_or_else(|| T::from_world(world)))
     }
 
@@ -562,7 +588,7 @@ impl<'a, T: Component + FromWorld> SystemParamFetch<'a> for LocalState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        _system_state: &'a SystemState,
+        _system_meta: &'a SystemMeta,
         _world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -601,6 +627,9 @@ impl<'a, T> RemovedComponents<'a, T> {
     }
 }
 
+// SAFE: Only reads World components
+unsafe impl<T: Component> ReadOnlySystemParamFetch for RemovedComponentsState<T> {}
+
 /// The [`SystemParamState`] of [`RemovedComponents`].
 pub struct RemovedComponentsState<T> {
     component_id: ComponentId,
@@ -616,7 +645,7 @@ impl<'a, T: Component> SystemParam for RemovedComponents<'a, T> {
 unsafe impl<T: Component> SystemParamState for RemovedComponentsState<T> {
     type Config = ();
 
-    fn init(world: &mut World, _system_state: &mut SystemState, _config: Self::Config) -> Self {
+    fn init(world: &mut World, _system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
         Self {
             component_id: world.components.get_or_insert_id::<T>(),
             marker: PhantomData,
@@ -632,7 +661,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for RemovedComponentsState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        _system_state: &'a SystemState,
+        _system_meta: &'a SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -661,6 +690,9 @@ pub struct NonSend<'w, T> {
     change_tick: u32,
 }
 
+// SAFE: Only reads a single World non-send resource
+unsafe impl<T> ReadOnlySystemParamFetch for NonSendState<T> {}
+
 impl<'w, T> Debug for NonSend<'w, T>
 where
     T: Debug,
@@ -703,20 +735,20 @@ impl<'a, T: 'static> SystemParam for NonSend<'a, T> {
     type Fetch = NonSendState<T>;
 }
 
-// SAFE: NonSendComponentId and ArchetypeComponentId access is applied to SystemState. If this
+// SAFE: NonSendComponentId and ArchetypeComponentId access is applied to SystemMeta. If this
 // NonSend conflicts with any prior access, a panic will occur.
 unsafe impl<T: 'static> SystemParamState for NonSendState<T> {
     type Config = ();
 
-    fn init(world: &mut World, system_state: &mut SystemState, _config: Self::Config) -> Self {
-        system_state.set_non_send();
+    fn init(world: &mut World, system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
+        system_meta.set_non_send();
 
         let component_id = world.initialize_non_send_resource::<T>();
-        let combined_access = system_state.component_access_set.combined_access_mut();
+        let combined_access = system_meta.component_access_set.combined_access_mut();
         if combined_access.has_write(component_id) {
             panic!(
                 "NonSend<{}> in system {} conflicts with a previous mutable resource access ({0}). Allowing this would break Rust's mutability rules. Consider removing the duplicate access.",
-                std::any::type_name::<T>(), system_state.name);
+                std::any::type_name::<T>(), system_meta.name);
         }
         combined_access.add_read(component_id);
 
@@ -724,7 +756,7 @@ unsafe impl<T: 'static> SystemParamState for NonSendState<T> {
         let archetype_component_id = resource_archetype
             .get_archetype_component_id(component_id)
             .unwrap();
-        system_state
+        system_meta
             .archetype_component_access
             .add_read(archetype_component_id);
         Self {
@@ -742,7 +774,7 @@ impl<'a, T: 'static> SystemParamFetch<'a> for NonSendState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_state: &'a SystemState,
+        system_meta: &'a SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -752,7 +784,7 @@ impl<'a, T: 'static> SystemParamFetch<'a> for NonSendState<T> {
             .unwrap_or_else(|| {
                 panic!(
                     "Non-send resource requested by {} does not exist: {}",
-                    system_state.name,
+                    system_meta.name,
                     std::any::type_name::<T>()
                 )
             });
@@ -760,7 +792,7 @@ impl<'a, T: 'static> SystemParamFetch<'a> for NonSendState<T> {
         NonSend {
             value: &*column.get_data_ptr().cast::<T>().as_ptr(),
             ticks: column.get_ticks_unchecked(0).clone(),
-            last_change_tick: system_state.last_change_tick,
+            last_change_tick: system_meta.last_change_tick,
             change_tick,
         }
     }
@@ -831,24 +863,24 @@ impl<'a, T: 'static> SystemParam for NonSendMut<'a, T> {
     type Fetch = NonSendMutState<T>;
 }
 
-// SAFE: NonSendMut ComponentId and ArchetypeComponentId access is applied to SystemState. If this
+// SAFE: NonSendMut ComponentId and ArchetypeComponentId access is applied to SystemMeta. If this
 // NonSendMut conflicts with any prior access, a panic will occur.
 unsafe impl<T: 'static> SystemParamState for NonSendMutState<T> {
     type Config = ();
 
-    fn init(world: &mut World, system_state: &mut SystemState, _config: Self::Config) -> Self {
-        system_state.set_non_send();
+    fn init(world: &mut World, system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
+        system_meta.set_non_send();
 
         let component_id = world.components.get_or_insert_non_send_resource_id::<T>();
-        let combined_access = system_state.component_access_set.combined_access_mut();
+        let combined_access = system_meta.component_access_set.combined_access_mut();
         if combined_access.has_write(component_id) {
             panic!(
                 "NonSendMut<{}> in system {} conflicts with a previous mutable resource access ({0}). Allowing this would break Rust's mutability rules. Consider removing the duplicate access.",
-                std::any::type_name::<T>(), system_state.name);
+                std::any::type_name::<T>(), system_meta.name);
         } else if combined_access.has_read(component_id) {
             panic!(
                 "NonSendMut<{}> in system {} conflicts with a previous immutable resource access ({0}). Allowing this would break Rust's mutability rules. Consider removing the duplicate access.",
-                std::any::type_name::<T>(), system_state.name);
+                std::any::type_name::<T>(), system_meta.name);
         }
         combined_access.add_write(component_id);
 
@@ -856,7 +888,7 @@ unsafe impl<T: 'static> SystemParamState for NonSendMutState<T> {
         let archetype_component_id = resource_archetype
             .get_archetype_component_id(component_id)
             .unwrap();
-        system_state
+        system_meta
             .archetype_component_access
             .add_write(archetype_component_id);
         Self {
@@ -874,7 +906,7 @@ impl<'a, T: 'static> SystemParamFetch<'a> for NonSendMutState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_state: &'a SystemState,
+        system_meta: &'a SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -884,14 +916,14 @@ impl<'a, T: 'static> SystemParamFetch<'a> for NonSendMutState<T> {
             .unwrap_or_else(|| {
                 panic!(
                     "Non-send resource requested by {} does not exist: {}",
-                    system_state.name,
+                    system_meta.name,
                     std::any::type_name::<T>()
                 )
             });
         NonSendMut {
             value: &mut *column.get_data_ptr().cast::<T>().as_ptr(),
             ticks: &mut *column.get_ticks_mut_ptr_unchecked(0),
-            last_change_tick: system_state.last_change_tick,
+            last_change_tick: system_meta.last_change_tick,
             change_tick,
         }
     }
@@ -901,6 +933,9 @@ impl<'a> SystemParam for &'a Archetypes {
     type Fetch = ArchetypesState;
 }
 
+// SAFE: Only reads World archetypes
+unsafe impl ReadOnlySystemParamFetch for ArchetypesState {}
+
 /// The [`SystemParamState`] of [`Archetypes`].
 pub struct ArchetypesState;
 
@@ -908,7 +943,7 @@ pub struct ArchetypesState;
 unsafe impl SystemParamState for ArchetypesState {
     type Config = ();
 
-    fn init(_world: &mut World, _system_state: &mut SystemState, _config: Self::Config) -> Self {
+    fn init(_world: &mut World, _system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
         Self
     }
 
@@ -921,7 +956,7 @@ impl<'a> SystemParamFetch<'a> for ArchetypesState {
     #[inline]
     unsafe fn get_param(
         _state: &'a mut Self,
-        _system_state: &'a SystemState,
+        _system_meta: &'a SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -933,6 +968,9 @@ impl<'a> SystemParam for &'a Components {
     type Fetch = ComponentsState;
 }
 
+// SAFE: Only reads World components
+unsafe impl ReadOnlySystemParamFetch for ComponentsState {}
+
 /// The [`SystemParamState`] of [`Components`].
 pub struct ComponentsState;
 
@@ -940,7 +978,7 @@ pub struct ComponentsState;
 unsafe impl SystemParamState for ComponentsState {
     type Config = ();
 
-    fn init(_world: &mut World, _system_state: &mut SystemState, _config: Self::Config) -> Self {
+    fn init(_world: &mut World, _system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
         Self
     }
 
@@ -953,7 +991,7 @@ impl<'a> SystemParamFetch<'a> for ComponentsState {
     #[inline]
     unsafe fn get_param(
         _state: &'a mut Self,
-        _system_state: &'a SystemState,
+        _system_meta: &'a SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -965,6 +1003,9 @@ impl<'a> SystemParam for &'a Entities {
     type Fetch = EntitiesState;
 }
 
+// SAFE: Only reads World entities
+unsafe impl ReadOnlySystemParamFetch for EntitiesState {}
+
 /// The [`SystemParamState`] of [`Entities`].
 pub struct EntitiesState;
 
@@ -972,7 +1013,7 @@ pub struct EntitiesState;
 unsafe impl SystemParamState for EntitiesState {
     type Config = ();
 
-    fn init(_world: &mut World, _system_state: &mut SystemState, _config: Self::Config) -> Self {
+    fn init(_world: &mut World, _system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
         Self
     }
 
@@ -985,7 +1026,7 @@ impl<'a> SystemParamFetch<'a> for EntitiesState {
     #[inline]
     unsafe fn get_param(
         _state: &'a mut Self,
-        _system_state: &'a SystemState,
+        _system_meta: &'a SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -997,6 +1038,9 @@ impl<'a> SystemParam for &'a Bundles {
     type Fetch = BundlesState;
 }
 
+// SAFE: Only reads World bundles
+unsafe impl ReadOnlySystemParamFetch for BundlesState {}
+
 /// The [`SystemParamState`] of [`Bundles`].
 pub struct BundlesState;
 
@@ -1004,7 +1048,7 @@ pub struct BundlesState;
 unsafe impl SystemParamState for BundlesState {
     type Config = ();
 
-    fn init(_world: &mut World, _system_state: &mut SystemState, _config: Self::Config) -> Self {
+    fn init(_world: &mut World, _system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
         Self
     }
 
@@ -1017,7 +1061,7 @@ impl<'a> SystemParamFetch<'a> for BundlesState {
     #[inline]
     unsafe fn get_param(
         _state: &'a mut Self,
-        _system_state: &'a SystemState,
+        _system_meta: &'a SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -1031,6 +1075,9 @@ pub struct SystemChangeTick {
     pub change_tick: u32,
 }
 
+// SAFE: Only reads internal system state
+unsafe impl ReadOnlySystemParamFetch for SystemChangeTickState {}
+
 impl SystemParam for SystemChangeTick {
     type Fetch = SystemChangeTickState;
 }
@@ -1041,7 +1088,7 @@ pub struct SystemChangeTickState {}
 unsafe impl SystemParamState for SystemChangeTickState {
     type Config = ();
 
-    fn init(_world: &mut World, _system_state: &mut SystemState, _config: Self::Config) -> Self {
+    fn init(_world: &mut World, _system_meta: &mut SystemMeta, _config: Self::Config) -> Self {
         Self {}
     }
 
@@ -1053,12 +1100,12 @@ impl<'a> SystemParamFetch<'a> for SystemChangeTickState {
 
     unsafe fn get_param(
         _state: &mut Self,
-        system_state: &SystemState,
+        system_meta: &SystemMeta,
         _world: &World,
         change_tick: u32,
     ) -> Self::Item {
         SystemChangeTick {
-            last_change_tick: system_state.last_change_tick,
+            last_change_tick: system_meta.last_change_tick,
             change_tick,
         }
     }
@@ -1069,6 +1116,10 @@ macro_rules! impl_system_param_tuple {
         impl<$($param: SystemParam),*> SystemParam for ($($param,)*) {
             type Fetch = ($($param::Fetch,)*);
         }
+
+        // SAFE: tuple consists only of ReadOnlySystemParamFetches
+        unsafe impl<$($param: ReadOnlySystemParamFetch),*> ReadOnlySystemParamFetch for ($($param,)*) {}
+
         #[allow(unused_variables)]
         #[allow(non_snake_case)]
         impl<'a, $($param: SystemParamFetch<'a>),*> SystemParamFetch<'a> for ($($param,)*) {
@@ -1077,13 +1128,13 @@ macro_rules! impl_system_param_tuple {
             #[inline]
             unsafe fn get_param(
                 state: &'a mut Self,
-                system_state: &'a SystemState,
+                system_meta: &'a SystemMeta,
                 world: &'a World,
                 change_tick: u32,
             ) -> Self::Item {
 
                 let ($($param,)*) = state;
-                ($($param::get_param($param, system_state, world, change_tick),)*)
+                ($($param::get_param($param, system_meta, world, change_tick),)*)
             }
         }
 
@@ -1092,15 +1143,15 @@ macro_rules! impl_system_param_tuple {
         unsafe impl<$($param: SystemParamState),*> SystemParamState for ($($param,)*) {
             type Config = ($(<$param as SystemParamState>::Config,)*);
             #[inline]
-            fn init(_world: &mut World, _system_state: &mut SystemState, config: Self::Config) -> Self {
+            fn init(_world: &mut World, _system_meta: &mut SystemMeta, config: Self::Config) -> Self {
                 let ($($param,)*) = config;
-                (($($param::init(_world, _system_state, $param),)*))
+                (($($param::init(_world, _system_meta, $param),)*))
             }
 
             #[inline]
-            fn new_archetype(&mut self, _archetype: &Archetype, _system_state: &mut SystemState) {
+            fn new_archetype(&mut self, _archetype: &Archetype, _system_meta: &mut SystemMeta) {
                 let ($($param,)*) = self;
-                $($param.new_archetype(_archetype, _system_state);)*
+                $($param.new_archetype(_archetype, _system_meta);)*
             }
 
             #[inline]

From fc720c6a5910c5178781c3bd18c0c40e0a93dd5a Mon Sep 17 00:00:00 2001
From: Carter Anderson <mcanders1@gmail.com>
Date: Tue, 1 Jun 2021 13:03:37 -0700
Subject: [PATCH 2/6] add change detection test

---
 crates/bevy_ecs/src/system/mod.rs | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/crates/bevy_ecs/src/system/mod.rs b/crates/bevy_ecs/src/system/mod.rs
index 6ba08a8a71c5b..b053b6cef825e 100644
--- a/crates/bevy_ecs/src/system/mod.rs
+++ b/crates/bevy_ecs/src/system/mod.rs
@@ -535,4 +535,30 @@ mod tests {
             "returned component matches initial value"
         );
     }
+
+    #[test]
+    fn system_param_change_detection() {
+        #[derive(Eq, PartialEq, Debug)]
+        struct A(usize);
+
+        let mut world = World::default();
+        let entity = world.spawn().insert(A(1)).id();
+
+        let mut system_state: SystemState<Query<&A, Changed<A>>> = SystemState::new(&mut world);
+        {
+            let query = system_state.get(&world);
+            assert_eq!(*query.single().unwrap(), A(1));
+        }
+
+        {
+            let query = system_state.get(&world);
+            assert!(query.single().is_err());
+        }
+
+        world.entity_mut(entity).get_mut::<A>().unwrap().0 = 2;
+        {
+            let query = system_state.get(&world);
+            assert_eq!(*query.single().unwrap(), A(2));
+        }
+    }
 }

From aded69e5f8e87a52fff0e713a31552442af649c9 Mon Sep 17 00:00:00 2001
From: Carter Anderson <mcanders1@gmail.com>
Date: Tue, 1 Jun 2021 13:04:14 -0700
Subject: [PATCH 3/6] fix SystemState change detection

---
 crates/bevy_ecs/macros/src/lib.rs             |  4 +--
 crates/bevy_ecs/src/system/function_system.rs | 14 +++-----
 crates/bevy_ecs/src/system/system_param.rs    | 32 +++++++++----------
 3 files changed, 23 insertions(+), 27 deletions(-)

diff --git a/crates/bevy_ecs/macros/src/lib.rs b/crates/bevy_ecs/macros/src/lib.rs
index de79099c1cda0..27383ff71ee55 100644
--- a/crates/bevy_ecs/macros/src/lib.rs
+++ b/crates/bevy_ecs/macros/src/lib.rs
@@ -276,7 +276,7 @@ pub fn impl_query_set(_input: TokenStream) -> TokenStream {
                 #[inline]
                 unsafe fn get_param(
                     state: &'a mut Self,
-                    system_meta: &'a SystemMeta,
+                    system_meta: &SystemMeta,
                     world: &'a World,
                     change_tick: u32,
                 ) -> Self::Item {
@@ -417,7 +417,7 @@ pub fn derive_system_param(input: TokenStream) -> TokenStream {
             type Item = #struct_name#ty_generics;
             unsafe fn get_param(
                 state: &'a mut Self,
-                system_meta: &'a #path::system::SystemMeta,
+                system_meta: &#path::system::SystemMeta,
                 world: &'a #path::world::World,
                 change_tick: u32,
             ) -> Self::Item {
diff --git a/crates/bevy_ecs/src/system/function_system.rs b/crates/bevy_ecs/src/system/function_system.rs
index 4c3bcf885f136..d7aad8e42a32a 100644
--- a/crates/bevy_ecs/src/system/function_system.rs
+++ b/crates/bevy_ecs/src/system/function_system.rs
@@ -56,7 +56,6 @@ impl SystemMeta {
 pub struct SystemState<Param: SystemParam> {
     meta: SystemMeta,
     param_state: <Param as SystemParam>::Fetch,
-    change_tick: u32,
 }
 
 impl<Param: SystemParam> SystemState<Param> {
@@ -71,11 +70,7 @@ impl<Param: SystemParam> SystemState<Param> {
     ) -> Self {
         let mut meta = SystemMeta::new::<Param>();
         let param_state = <Param::Fetch as SystemParamState>::init(world, &mut meta, config);
-        Self {
-            meta,
-            param_state,
-            change_tick: 0,
-        }
+        Self { meta, param_state }
     }
 
     #[inline]
@@ -120,13 +115,14 @@ impl<Param: SystemParam> SystemState<Param> {
         world: &'a World,
     ) -> <Param::Fetch as SystemParamFetch<'a>>::Item {
         let change_tick = world.increment_change_tick();
-        self.change_tick = change_tick;
-        <Param::Fetch as SystemParamFetch>::get_param(
+        let param = <Param::Fetch as SystemParamFetch>::get_param(
             &mut self.param_state,
             &self.meta,
             world,
             change_tick,
-        )
+        );
+        self.meta.last_change_tick = change_tick;
+        param
     }
 }
 
diff --git a/crates/bevy_ecs/src/system/system_param.rs b/crates/bevy_ecs/src/system/system_param.rs
index 9cd46476593bc..95dd4cee1bc83 100644
--- a/crates/bevy_ecs/src/system/system_param.rs
+++ b/crates/bevy_ecs/src/system/system_param.rs
@@ -88,7 +88,7 @@ pub trait SystemParamFetch<'a>: SystemParamState {
     /// access is safe in the context of the system scheduler.
     unsafe fn get_param(
         state: &'a mut Self,
-        system_meta: &'a SystemMeta,
+        system_meta: &SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item;
@@ -155,7 +155,7 @@ where
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_meta: &'a SystemMeta,
+        system_meta: &SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -292,7 +292,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for ResState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_meta: &'a SystemMeta,
+        system_meta: &SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -340,7 +340,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for OptionResState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_meta: &'a SystemMeta,
+        system_meta: &SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -406,7 +406,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for ResMutState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_meta: &'a SystemMeta,
+        system_meta: &SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -453,7 +453,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for OptionResMutState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_meta: &'a SystemMeta,
+        system_meta: &SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -498,7 +498,7 @@ impl<'a> SystemParamFetch<'a> for CommandQueue {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        _system_meta: &'a SystemMeta,
+        _system_meta: &SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -588,7 +588,7 @@ impl<'a, T: Component + FromWorld> SystemParamFetch<'a> for LocalState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        _system_meta: &'a SystemMeta,
+        _system_meta: &SystemMeta,
         _world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -661,7 +661,7 @@ impl<'a, T: Component> SystemParamFetch<'a> for RemovedComponentsState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        _system_meta: &'a SystemMeta,
+        _system_meta: &SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -774,7 +774,7 @@ impl<'a, T: 'static> SystemParamFetch<'a> for NonSendState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_meta: &'a SystemMeta,
+        system_meta: &SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -906,7 +906,7 @@ impl<'a, T: 'static> SystemParamFetch<'a> for NonSendMutState<T> {
     #[inline]
     unsafe fn get_param(
         state: &'a mut Self,
-        system_meta: &'a SystemMeta,
+        system_meta: &SystemMeta,
         world: &'a World,
         change_tick: u32,
     ) -> Self::Item {
@@ -956,7 +956,7 @@ impl<'a> SystemParamFetch<'a> for ArchetypesState {
     #[inline]
     unsafe fn get_param(
         _state: &'a mut Self,
-        _system_meta: &'a SystemMeta,
+        _system_meta: &SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -991,7 +991,7 @@ impl<'a> SystemParamFetch<'a> for ComponentsState {
     #[inline]
     unsafe fn get_param(
         _state: &'a mut Self,
-        _system_meta: &'a SystemMeta,
+        _system_meta: &SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -1026,7 +1026,7 @@ impl<'a> SystemParamFetch<'a> for EntitiesState {
     #[inline]
     unsafe fn get_param(
         _state: &'a mut Self,
-        _system_meta: &'a SystemMeta,
+        _system_meta: &SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -1061,7 +1061,7 @@ impl<'a> SystemParamFetch<'a> for BundlesState {
     #[inline]
     unsafe fn get_param(
         _state: &'a mut Self,
-        _system_meta: &'a SystemMeta,
+        _system_meta: &SystemMeta,
         world: &'a World,
         _change_tick: u32,
     ) -> Self::Item {
@@ -1128,7 +1128,7 @@ macro_rules! impl_system_param_tuple {
             #[inline]
             unsafe fn get_param(
                 state: &'a mut Self,
-                system_meta: &'a SystemMeta,
+                system_meta: &SystemMeta,
                 world: &'a World,
                 change_tick: u32,
             ) -> Self::Item {

From 4b038ed066be5d2745714cc1d409034d321197ab Mon Sep 17 00:00:00 2001
From: Carter Anderson <mcanders1@gmail.com>
Date: Tue, 1 Jun 2021 13:12:24 -0700
Subject: [PATCH 4/6] Mark SystemParamFunction::run as unsafe. inline
 get/get_mut

---
 crates/bevy_ecs/src/system/function_system.rs | 24 ++++++++++---------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/crates/bevy_ecs/src/system/function_system.rs b/crates/bevy_ecs/src/system/function_system.rs
index d7aad8e42a32a..06186347d5ce5 100644
--- a/crates/bevy_ecs/src/system/function_system.rs
+++ b/crates/bevy_ecs/src/system/function_system.rs
@@ -79,6 +79,7 @@ impl<Param: SystemParam> SystemState<Param> {
     }
 
     /// Retrieve the [`SystemParam`] values. This can only be called when all parameters are read-only.
+    #[inline]
     pub fn get<'a>(&'a mut self, world: &'a World) -> <Param::Fetch as SystemParamFetch<'a>>::Item
     where
         Param::Fetch: ReadOnlySystemParamFetch,
@@ -88,6 +89,7 @@ impl<Param: SystemParam> SystemState<Param> {
     }
 
     /// Retrieve the mutable [`SystemParam`] values.
+    #[inline]
     pub fn get_mut<'a>(
         &'a mut self,
         world: &'a mut World,
@@ -327,7 +329,11 @@ where
 
 /// A trait implemented for all functions that can be used as [`System`]s.
 pub trait SystemParamFunction<In, Out, Param: SystemParam, Marker>: Send + Sync + 'static {
-    fn run(
+    /// # Safety
+    ///
+    /// This call might access any of the input parameters in an unsafe way. Make sure the data
+    /// access is safe in the context of the system scheduler.
+    unsafe fn run(
         &mut self,
         input: In,
         state: &mut Param::Fetch,
@@ -347,11 +353,9 @@ macro_rules! impl_system_function {
                 FnMut($(<<$param as SystemParam>::Fetch as SystemParamFetch>::Item),*) -> Out + Send + Sync + 'static, Out: 'static
         {
             #[inline]
-            fn run(&mut self, _input: (), state: &mut <($($param,)*) as SystemParam>::Fetch, system_meta: &SystemMeta, world: &World, change_tick: u32) -> Out {
-                unsafe {
-                    let ($($param,)*) = <<($($param,)*) as SystemParam>::Fetch as SystemParamFetch>::get_param(state, system_meta, world, change_tick);
-                    self($($param),*)
-                }
+            unsafe fn run(&mut self, _input: (), state: &mut <($($param,)*) as SystemParam>::Fetch, system_meta: &SystemMeta, world: &World, change_tick: u32) -> Out {
+                let ($($param,)*) = <<($($param,)*) as SystemParam>::Fetch as SystemParamFetch>::get_param(state, system_meta, world, change_tick);
+                self($($param),*)
             }
         }
 
@@ -363,11 +367,9 @@ macro_rules! impl_system_function {
                 FnMut(In<Input>, $(<<$param as SystemParam>::Fetch as SystemParamFetch>::Item),*) -> Out + Send + Sync + 'static, Out: 'static
         {
             #[inline]
-            fn run(&mut self, input: Input, state: &mut <($($param,)*) as SystemParam>::Fetch, system_meta: &SystemMeta, world: &World, change_tick: u32) -> Out {
-                unsafe {
-                    let ($($param,)*) = <<($($param,)*) as SystemParam>::Fetch as SystemParamFetch>::get_param(state, system_meta, world, change_tick);
-                    self(In(input), $($param),*)
-                }
+            unsafe fn run(&mut self, input: Input, state: &mut <($($param,)*) as SystemParam>::Fetch, system_meta: &SystemMeta, world: &World, change_tick: u32) -> Out {
+                let ($($param,)*) = <<($($param,)*) as SystemParam>::Fetch as SystemParamFetch>::get_param(state, system_meta, world, change_tick);
+                self(In(input), $($param),*)
             }
         }
     };

From 4a1524907c50495207a12b2c2cd4d9f828013fbd Mon Sep 17 00:00:00 2001
From: Carter Anderson <mcanders1@gmail.com>
Date: Tue, 1 Jun 2021 17:16:48 -0700
Subject: [PATCH 5/6] World validation

---
 crates/bevy_ecs/src/system/function_system.rs | 28 +++++++++++++++----
 crates/bevy_ecs/src/system/mod.rs             | 15 ++++++++--
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/crates/bevy_ecs/src/system/function_system.rs b/crates/bevy_ecs/src/system/function_system.rs
index 06186347d5ce5..7307aef5f3482 100644
--- a/crates/bevy_ecs/src/system/function_system.rs
+++ b/crates/bevy_ecs/src/system/function_system.rs
@@ -6,7 +6,7 @@ use crate::{
         check_system_change_tick, ReadOnlySystemParamFetch, System, SystemId, SystemParam,
         SystemParamFetch, SystemParamState,
     },
-    world::World,
+    world::{World, WorldId},
 };
 use bevy_ecs_macros::all_tuples;
 use std::{borrow::Cow, marker::PhantomData};
@@ -56,6 +56,7 @@ impl SystemMeta {
 pub struct SystemState<Param: SystemParam> {
     meta: SystemMeta,
     param_state: <Param as SystemParam>::Fetch,
+    world_id: WorldId,
 }
 
 impl<Param: SystemParam> SystemState<Param> {
@@ -70,7 +71,11 @@ impl<Param: SystemParam> SystemState<Param> {
     ) -> Self {
         let mut meta = SystemMeta::new::<Param>();
         let param_state = <Param::Fetch as SystemParamState>::init(world, &mut meta, config);
-        Self { meta, param_state }
+        Self {
+            meta,
+            param_state,
+            world_id: world.id(),
+        }
     }
 
     #[inline]
@@ -84,7 +89,8 @@ impl<Param: SystemParam> SystemState<Param> {
     where
         Param::Fetch: ReadOnlySystemParamFetch,
     {
-        // SAFE: Param is read-only and doesn't allow mutable access to World
+        self.validate_world(world);
+        // SAFE: Param is read-only and doesn't allow mutable access to World. It also matches the World this SystemState was created with
         unsafe { self.get_unchecked(world) }
     }
 
@@ -94,7 +100,8 @@ impl<Param: SystemParam> SystemState<Param> {
         &'a mut self,
         world: &'a mut World,
     ) -> <Param::Fetch as SystemParamFetch<'a>>::Item {
-        // SAFE: World is uniquely borrowed
+        self.validate_world(world);
+        // SAFE: World is uniquely borrowed and matches the World this SystemState was created with
         unsafe { self.get_unchecked(world) }
     }
 
@@ -106,11 +113,22 @@ impl<Param: SystemParam> SystemState<Param> {
         self.param_state.apply(world);
     }
 
+    #[inline]
+    pub fn matches_world(&self, world: &World) -> bool {
+        self.world_id == world.id()
+    }
+
+    #[inline]
+    fn validate_world(&self, world: &World) {
+        assert!(self.matches_world(world), "Encountered a mismatched World. A SystemState cannot be used with Worlds other than the one it was created with.")
+    }
+
     /// Retrieve the [`SystemParam`] values.
     ///
     /// # Safety
     /// This call might access any of the input parameters in a way that violates Rust's mutability rules. Make sure the data
-    /// access is safe in the context of global [`World`] access.
+    /// access is safe in the context of global [`World`] access. The passed-in [`World`] _must_ be the [`World`] the [`SystemState`] was
+    /// created with.   
     #[inline]
     pub unsafe fn get_unchecked<'a>(
         &'a mut self,
diff --git a/crates/bevy_ecs/src/system/mod.rs b/crates/bevy_ecs/src/system/mod.rs
index b053b6cef825e..2c12e422c19d3 100644
--- a/crates/bevy_ecs/src/system/mod.rs
+++ b/crates/bevy_ecs/src/system/mod.rs
@@ -487,7 +487,7 @@ mod tests {
     }
 
     #[test]
-    fn read_system_param() {
+    fn read_system_state() {
         #[derive(Eq, PartialEq, Debug)]
         struct A(usize);
 
@@ -510,7 +510,7 @@ mod tests {
     }
 
     #[test]
-    fn write_system_param() {
+    fn write_system_state() {
         #[derive(Eq, PartialEq, Debug)]
         struct A(usize);
 
@@ -537,7 +537,7 @@ mod tests {
     }
 
     #[test]
-    fn system_param_change_detection() {
+    fn system_state_change_detection() {
         #[derive(Eq, PartialEq, Debug)]
         struct A(usize);
 
@@ -561,4 +561,13 @@ mod tests {
             assert_eq!(*query.single().unwrap(), A(2));
         }
     }
+
+    #[test]
+    #[should_panic]
+    fn system_state_invalid_world() {
+        let mut world = World::default();
+        let mut system_state = SystemState::<Query<&A>>::new(&mut world);
+        let mismatched_world = World::default();
+        system_state.get(&mismatched_world);
+    }
 }

From a3f1b20f680bf50d1d3b692f018eb3326657d8ed Mon Sep 17 00:00:00 2001
From: Carter Anderson <mcanders1@gmail.com>
Date: Tue, 1 Jun 2021 17:38:53 -0700
Subject: [PATCH 6/6] Update archetypes automatically

---
 crates/bevy_ecs/src/system/function_system.rs | 36 ++++++++++++-------
 crates/bevy_ecs/src/system/mod.rs             | 32 +++++++++++++++++
 2 files changed, 56 insertions(+), 12 deletions(-)

diff --git a/crates/bevy_ecs/src/system/function_system.rs b/crates/bevy_ecs/src/system/function_system.rs
index 7307aef5f3482..414ba2c3fec26 100644
--- a/crates/bevy_ecs/src/system/function_system.rs
+++ b/crates/bevy_ecs/src/system/function_system.rs
@@ -1,5 +1,5 @@
 use crate::{
-    archetype::{Archetype, ArchetypeComponentId},
+    archetype::{Archetype, ArchetypeComponentId, ArchetypeGeneration, ArchetypeId},
     component::ComponentId,
     query::{Access, FilteredAccessSet},
     system::{
@@ -57,6 +57,7 @@ pub struct SystemState<Param: SystemParam> {
     meta: SystemMeta,
     param_state: <Param as SystemParam>::Fetch,
     world_id: WorldId,
+    archetype_generation: ArchetypeGeneration,
 }
 
 impl<Param: SystemParam> SystemState<Param> {
@@ -75,6 +76,7 @@ impl<Param: SystemParam> SystemState<Param> {
             meta,
             param_state,
             world_id: world.id(),
+            archetype_generation: ArchetypeGeneration::initial(),
         }
     }
 
@@ -89,9 +91,9 @@ impl<Param: SystemParam> SystemState<Param> {
     where
         Param::Fetch: ReadOnlySystemParamFetch,
     {
-        self.validate_world(world);
-        // SAFE: Param is read-only and doesn't allow mutable access to World. It also matches the World this SystemState was created with
-        unsafe { self.get_unchecked(world) }
+        self.validate_world_and_update_archetypes(world);
+        // SAFE: Param is read-only and doesn't allow mutable access to World. It also matches the World this SystemState was created with.
+        unsafe { self.get_unchecked_manual(world) }
     }
 
     /// Retrieve the mutable [`SystemParam`] values.
@@ -100,9 +102,9 @@ impl<Param: SystemParam> SystemState<Param> {
         &'a mut self,
         world: &'a mut World,
     ) -> <Param::Fetch as SystemParamFetch<'a>>::Item {
-        self.validate_world(world);
-        // SAFE: World is uniquely borrowed and matches the World this SystemState was created with
-        unsafe { self.get_unchecked(world) }
+        self.validate_world_and_update_archetypes(world);
+        // SAFE: World is uniquely borrowed and matches the World this SystemState was created with.
+        unsafe { self.get_unchecked_manual(world) }
     }
 
     /// Applies all state queued up for [`SystemParam`] values. For example, this will apply commands queued up
@@ -118,19 +120,29 @@ impl<Param: SystemParam> SystemState<Param> {
         self.world_id == world.id()
     }
 
-    #[inline]
-    fn validate_world(&self, world: &World) {
-        assert!(self.matches_world(world), "Encountered a mismatched World. A SystemState cannot be used with Worlds other than the one it was created with.")
+    fn validate_world_and_update_archetypes(&mut self, world: &World) {
+        assert!(self.matches_world(world), "Encountered a mismatched World. A SystemState cannot be used with Worlds other than the one it was created with.");
+        let archetypes = world.archetypes();
+        let new_generation = archetypes.generation();
+        let old_generation = std::mem::replace(&mut self.archetype_generation, new_generation);
+        let archetype_index_range = old_generation.value()..new_generation.value();
+
+        for archetype_index in archetype_index_range {
+            self.param_state.new_archetype(
+                &archetypes[ArchetypeId::new(archetype_index)],
+                &mut self.meta,
+            );
+        }
     }
 
-    /// Retrieve the [`SystemParam`] values.
+    /// Retrieve the [`SystemParam`] values. This will not update archetypes automatically.
     ///
     /// # Safety
     /// This call might access any of the input parameters in a way that violates Rust's mutability rules. Make sure the data
     /// access is safe in the context of global [`World`] access. The passed-in [`World`] _must_ be the [`World`] the [`SystemState`] was
     /// created with.   
     #[inline]
-    pub unsafe fn get_unchecked<'a>(
+    pub unsafe fn get_unchecked_manual<'a>(
         &'a mut self,
         world: &'a World,
     ) -> <Param::Fetch as SystemParamFetch<'a>>::Item {
diff --git a/crates/bevy_ecs/src/system/mod.rs b/crates/bevy_ecs/src/system/mod.rs
index 2c12e422c19d3..06fdf53ce6eaa 100644
--- a/crates/bevy_ecs/src/system/mod.rs
+++ b/crates/bevy_ecs/src/system/mod.rs
@@ -570,4 +570,36 @@ mod tests {
         let mismatched_world = World::default();
         system_state.get(&mismatched_world);
     }
+
+    #[test]
+    fn system_state_archetype_update() {
+        #[derive(Eq, PartialEq, Debug)]
+        struct A(usize);
+
+        #[derive(Eq, PartialEq, Debug)]
+        struct B(usize);
+
+        let mut world = World::default();
+        world.spawn().insert(A(1));
+
+        let mut system_state = SystemState::<Query<&A>>::new(&mut world);
+        {
+            let query = system_state.get(&world);
+            assert_eq!(
+                query.iter().collect::<Vec<_>>(),
+                vec![&A(1)],
+                "exactly one component returned"
+            );
+        }
+
+        world.spawn().insert_bundle((A(2), B(2)));
+        {
+            let query = system_state.get(&world);
+            assert_eq!(
+                query.iter().collect::<Vec<_>>(),
+                vec![&A(1), &A(2)],
+                "components from both archetypes returned"
+            );
+        }
+    }
 }