Replace custom_where attribute with where

crates/bevy_asset/src/handle.rs

@@ -122,7 +122,7 @@ impl std::fmt::Debug for StrongHandle {
 /// [`Handle::Strong`] also provides access to useful [`Asset`] metadata, such as the [`AssetPath`] (if it exists).
 #[derive(Component, Reflect)]
 #[reflect(Component)]
-#[reflect(custom_where(A: Asset))]
+#[reflect(where A: Asset)]
 pub enum Handle<A: Asset> {
     /// A "strong" reference to a live (or loading) [`Asset`]. If a [`Handle`] is [`Handle::Strong`], the [`Asset`] will be kept
     /// alive until the [`Handle`] is dropped. Strong handles also provide access to additional asset metadata.

crates/bevy_asset/src/id.rs

@@ -17,7 +17,7 @@ use thiserror::Error;
 ///
 /// For an "untyped" / "generic-less" id, see [`UntypedAssetId`].
 #[derive(Reflect)]
-#[reflect(custom_where(A: Asset))]
+#[reflect(where A: Asset)]
 pub enum AssetId<A: Asset> {
     /// A small / efficient runtime identifier that can be used to efficiently look up an asset stored in [`Assets`]. This is
     /// the "default" identifier used for assets. The alternative(s) (ex: [`AssetId::Uuid`]) will only be used if assets are

crates/bevy_reflect/bevy_reflect_derive/src/container_attributes.rs

@@ -7,13 +7,13 @@
 
 use crate::utility;
 use bevy_macro_utils::fq_std::{FQAny, FQOption};
-use proc_macro2::{Ident, Span};
+use proc_macro2::{Ident, Span, TokenTree};
 use quote::quote_spanned;
 use syn::parse::{Parse, ParseStream};
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
 use syn::token::Comma;
-use syn::{Expr, LitBool, Meta, Path, Token, WherePredicate};
+use syn::{Expr, LitBool, Meta, MetaList, Path, WhereClause};
 
 // The "special" trait idents that are used internally for reflection.
 // Received via attributes like `#[reflect(PartialEq, Hash, ...)]`
@@ -31,9 +31,6 @@ const FROM_REFLECT_ATTR: &str = "from_reflect";
 // Attributes for `TypePath` implementation
 const TYPE_PATH_ATTR: &str = "type_path";
 
-// Attributes for `Reflect` implementation
-const CUSTOM_WHERE_ATTR: &str = "custom_where";
-
 // The error message to show when a trait/type is specified multiple times
 const CONFLICTING_TYPE_DATA_MESSAGE: &str = "conflicting type data registration";
 
@@ -214,12 +211,30 @@ pub(crate) struct ReflectTraits {
     partial_eq: TraitImpl,
     from_reflect_attrs: FromReflectAttrs,
     type_path_attrs: TypePathAttrs,
-    custom_where: Option<Punctuated<WherePredicate, Token![,]>>,
+    custom_where: Option<WhereClause>,
     idents: Vec<Ident>,
 }
 
 impl ReflectTraits {
-    pub fn from_metas(
+    pub fn from_meta_list(
+        meta: &MetaList,
+        is_from_reflect_derive: bool,
+    ) -> Result<Self, syn::Error> {
+        match meta.tokens.clone().into_iter().next() {
+            // Handles `#[reflect(where T: Trait, U::Assoc: Trait)]`
+            Some(TokenTree::Ident(ident)) if ident == "where" => {
+                let mut traits = ReflectTraits::default();
+                traits.custom_where = Some(meta.parse_args::<WhereClause>()?);
+                Ok(traits)
+            }
+            _ => Self::from_metas(
+                meta.parse_args_with(Punctuated::<Meta, Comma>::parse_terminated)?,
+                is_from_reflect_derive,
+            ),
+        }
+    }
+
+    fn from_metas(
         metas: Punctuated<Meta, Comma>,
         is_from_reflect_derive: bool,
     ) -> Result<Self, syn::Error> {
@@ -257,12 +272,6 @@ impl ReflectTraits {
                         }
                     }
                 }
-                // Handles `#[reflect(custom_where(T: Trait, U::Assoc: Trait))]`
-                Meta::List(list) if list.path.is_ident(CUSTOM_WHERE_ATTR) => {
-                    let predicate: Punctuated<WherePredicate, Token![,]> =
-                        list.parse_args_with(Punctuated::parse_terminated)?;
-                    traits.merge_custom_where(Some(predicate));
-                }
                 // Handles `#[reflect( Debug(custom_debug_fn) )]`
                 Meta::List(list) if list.path.is_ident(DEBUG_ATTR) => {
                     let ident = list.path.get_ident().unwrap();
@@ -290,7 +299,9 @@ impl ReflectTraits {
                 Meta::List(list) => {
                     return Err(syn::Error::new_spanned(
                         list,
-                        format!("expected one of [{DEBUG_ATTR:?}, {PARTIAL_EQ_ATTR:?}, {HASH_ATTR:?}, {CUSTOM_WHERE_ATTR:?}]")
+                        format!(
+                            "expected one of [{DEBUG_ATTR:?}, {PARTIAL_EQ_ATTR:?}, {HASH_ATTR:?}]"
+                        ),
                     ));
                 }
                 Meta::NameValue(pair) => {
@@ -408,7 +419,7 @@ impl ReflectTraits {
         }
     }
 
-    pub fn custom_where(&self) -> Option<&Punctuated<WherePredicate, Token![,]>> {
+    pub fn custom_where(&self) -> Option<&WhereClause> {
         self.custom_where.as_ref()
     }
 
@@ -430,10 +441,10 @@ impl ReflectTraits {
         Ok(())
     }
 
-    fn merge_custom_where(&mut self, other: Option<Punctuated<WherePredicate, Token![,]>>) {
+    fn merge_custom_where(&mut self, other: Option<WhereClause>) {
         match (&mut self.custom_where, other) {
             (Some(this), Some(other)) => {
-                this.extend(other);
+                this.predicates.extend(other.predicates);
             }
             (None, Some(other)) => {
                 self.custom_where = Some(other);

crates/bevy_reflect/bevy_reflect_derive/src/derive_data.rs

@@ -167,10 +167,8 @@ impl<'a> ReflectDerive<'a> {
                     }
 
                     reflect_mode = Some(ReflectMode::Normal);
-                    let new_traits = ReflectTraits::from_metas(
-                        meta_list.parse_args_with(Punctuated::<Meta, Comma>::parse_terminated)?,
-                        is_from_reflect_derive,
-                    )?;
+                    let new_traits =
+                        ReflectTraits::from_meta_list(meta_list, is_from_reflect_derive)?;
                     traits.merge(new_traits)?;
                 }
                 Meta::List(meta_list) if meta_list.path.is_ident(REFLECT_VALUE_ATTRIBUTE_NAME) => {
@@ -182,10 +180,8 @@ impl<'a> ReflectDerive<'a> {
                     }
 
                     reflect_mode = Some(ReflectMode::Value);
-                    let new_traits = ReflectTraits::from_metas(
-                        meta_list.parse_args_with(Punctuated::<Meta, Comma>::parse_terminated)?,
-                        is_from_reflect_derive,
-                    )?;
+                    let new_traits =
+                        ReflectTraits::from_meta_list(meta_list, is_from_reflect_derive)?;
                     traits.merge(new_traits)?;
                 }
                 Meta::Path(path) if path.is_ident(REFLECT_VALUE_ATTRIBUTE_NAME) => {

crates/bevy_reflect/bevy_reflect_derive/src/lib.rs

@@ -131,7 +131,7 @@ pub(crate) static TYPE_NAME_ATTRIBUTE_NAME: &str = "type_name";
 /// This is useful for when a type can't or shouldn't implement `TypePath`,
 /// or if a manual implementation is desired.
 ///
-/// ## `#[reflect(custom_where(T: Trait, U::Assoc: Trait, ...))]`
+/// ## `#[reflect(where T: Trait, U::Assoc: Trait, ...)]`
 ///
 /// By default, the derive macro will automatically add certain trait bounds to all generic type parameters
 /// in order to make them compatible with reflection without the user needing to add them manually.
@@ -147,7 +147,7 @@ pub(crate) static TYPE_NAME_ATTRIBUTE_NAME: &str = "type_name";
 /// in general.
 ///
 /// This means that if you want to opt-out of the default bounds for _all_ type parameters,
-/// you can add `#[reflect(custom_where())]` to the container item to indicate
+/// you can add `#[reflect(where)]` to the container item to indicate
 /// that an empty `where` clause should be used.
 ///
 /// ### Example
@@ -158,7 +158,7 @@ pub(crate) static TYPE_NAME_ATTRIBUTE_NAME: &str = "type_name";
 /// }
 ///
 /// #[derive(Reflect)]
-/// #[reflect(custom_where(T::Assoc: FromReflect))]
+/// #[reflect(where T::Assoc: FromReflect)]
 /// struct Foo<T: Trait> where T::Assoc: Default {
 ///   value: T::Assoc,
 /// }
@@ -192,7 +192,7 @@ pub(crate) static TYPE_NAME_ATTRIBUTE_NAME: &str = "type_name";
 /// or allowing the use of types that do not implement `Reflect` within the container.
 ///
 /// If the field contains a generic type parameter, you will likely need to add a
-/// [`#[reflect(custom_where())]`](#reflectcustom_wheret-trait-uassoc-trait-)
+/// [`#[reflect(where)]`](#reflectwheret-trait-uassoc-trait-)
 /// attribute to the container in order to avoid the default bounds being applied to the type parameter.
 ///
 /// ## `#[reflect(skip_serializing)]`

crates/bevy_reflect/bevy_reflect_derive/src/utility.rs

@@ -112,7 +112,7 @@ impl<'a, 'b> WhereClauseOptions<'a, 'b> {
     ///
     /// This will only add bounds for generic type parameters.
     ///
-    /// If the container has a `#[reflect(custom_where(...))]` attribute,
+    /// If the container has a `#[reflect(where)]` attribute,
     /// this method will extend the type parameters with the _required_ bounds.
     /// If the attribute is not present, it will extend the type parameters with the _additional_ bounds.
     ///
@@ -138,7 +138,7 @@ impl<'a, 'b> WhereClauseOptions<'a, 'b> {
     ///
     /// It has type parameters `T` and `U`.
     ///
-    /// Since there is no `#[reflect(custom_where(...))]` attribute, this method will extend the type parameters
+    /// Since there is no `#[reflect(where)]` attribute, this method will extend the type parameters
     /// with the additional bounds:
     ///
     /// ```ignore (bevy_reflect is not accessible from this crate)
@@ -150,15 +150,15 @@ impl<'a, 'b> WhereClauseOptions<'a, 'b> {
     /// If we had this struct:
     /// ```ignore (bevy_reflect is not accessible from this crate)
     /// #[derive(Reflect)]
-    /// #[reflect(custom_where(T: FromReflect + Default))]
+    /// #[reflect(where T: FromReflect + Default)]
     /// struct Foo<T, U> {
     ///   a: T,
     ///   #[reflect(ignore)]
     ///   b: U
     /// }
     /// ```
     ///
-    /// Since there is a `#[reflect(custom_where(...))]` attribute, this method will extend the type parameters
+    /// Since there is a `#[reflect(where)]` attribute, this method will extend the type parameters
     /// with _just_ the required bounds along with the predicates specified in the attribute:
     ///
     /// ```ignore (bevy_reflect is not accessible from this crate)
@@ -181,7 +181,11 @@ impl<'a, 'b> WhereClauseOptions<'a, 'b> {
 
         // Add additional reflection trait bounds
         let types = self.type_param_idents();
-        let custom_where = self.meta.traits().custom_where();
+        let custom_where = self
+            .meta
+            .traits()
+            .custom_where()
+            .map(|clause| &clause.predicates);
         let trait_bounds = self.trait_bounds();
 
         generic_where_clause.extend(quote! {

crates/bevy_reflect/src/lib.rs

@@ -541,6 +541,7 @@ mod tests {
         ser::{to_string_pretty, PrettyConfig},
         Deserializer,
     };
+    use static_assertions::{assert_impl_all, assert_not_impl_all};
     use std::{
         any::TypeId,
         borrow::Cow,
@@ -1866,47 +1867,46 @@ bevy_reflect::tests::Test {
     #[test]
     fn should_allow_custom_where() {
         #[derive(Reflect)]
-        #[reflect(custom_where(T: Default))]
+        #[reflect(where T: Default)]
         struct Foo<T>(String, #[reflect(ignore)] PhantomData<T>);
 
         #[derive(Default, TypePath)]
         struct Bar;
 
-        #[derive(Reflect)]
-        struct Baz {
-            a: Foo<Bar>,
-            b: Foo<usize>,
-        }
+        #[derive(TypePath)]
+        struct Baz;
+
+        assert_impl_all!(Foo<Bar>: Reflect);
+        assert_not_impl_all!(Foo<Baz>: Reflect);
     }
 
     #[test]
     fn should_allow_empty_custom_where() {
         #[derive(Reflect)]
-        #[reflect(custom_where())]
+        #[reflect(where)]
         struct Foo<T>(String, #[reflect(ignore)] PhantomData<T>);
 
         #[derive(TypePath)]
         struct Bar;
 
-        #[derive(Reflect)]
-        struct Baz {
-            a: Foo<Bar>,
-            b: Foo<usize>,
-        }
+        assert_impl_all!(Foo<Bar>: Reflect);
     }
 
     #[test]
     fn should_allow_multiple_custom_where() {
         #[derive(Reflect)]
-        #[reflect(custom_where(T: Default + FromReflect))]
-        #[reflect(custom_where(U: std::ops::Add<T> + FromReflect))]
+        #[reflect(where T: Default + FromReflect)]
+        #[reflect(where U: std::ops::Add<T> + FromReflect)]
         struct Foo<T, U>(T, U);
 
         #[derive(Reflect)]
         struct Baz {
             a: Foo<i32, i32>,
             b: Foo<u32, u32>,
         }
+
+        assert_impl_all!(Foo<i32, i32>: Reflect);
+        assert_not_impl_all!(Foo<i32, usize>: Reflect);
     }
 
     #[test]
@@ -1917,7 +1917,7 @@ bevy_reflect::tests::Test {
 
         // We don't need `T` to be `Reflect` since we only care about `T::Assoc`
         #[derive(Reflect)]
-        #[reflect(custom_where(T::Assoc: FromReflect))]
+        #[reflect(where T::Assoc: FromReflect)]
         struct Foo<T: Trait>(T::Assoc);
 
         #[derive(TypePath)]
@@ -1927,10 +1927,7 @@ bevy_reflect::tests::Test {
             type Assoc = usize;
         }
 
-        #[derive(Reflect)]
-        struct Baz {
-            a: Foo<Bar>,
-        }
+        assert_impl_all!(Foo<Bar>: Reflect);
     }
 
     #[test]
@@ -1969,7 +1966,7 @@ bevy_reflect::tests::Test {
     fn can_opt_out_type_path() {
         #[derive(Reflect)]
         #[reflect(type_path = false)]
-        #[reflect(custom_where())]
+        #[reflect(where)]
         struct Foo<T> {
             #[reflect(ignore)]
             _marker: PhantomData<T>,