Make reflect_partial_eq return more accurate results (bevyengine#5210)

# Objective

Closes bevyengine#5204

## Solution

- Followed @nicopap suggestion on bevyengine#4761 (comment)

## Changelog

- [x] Updated [struct_trait](https://github.com/bevyengine/bevy/blob/dfe969005264fff54060f9fb148639f80f9cfb29/crates/bevy_reflect/src/struct_trait.rs#L455-L457), [tuple_struct](https://github.com/bevyengine/bevy/blob/dfe969005264fff54060f9fb148639f80f9cfb29/crates/bevy_reflect/src/tuple_struct.rs#L366-L368), [tuple](https://github.com/bevyengine/bevy/blob/dfe969005264fff54060f9fb148639f80f9cfb29/crates/bevy_reflect/src/tuple.rs#L386), [array](https://github.com/bevyengine/bevy/blob/dfe969005264fff54060f9fb148639f80f9cfb29/crates/bevy_reflect/src/array.rs#L335-L337), [list](https://github.com/bevyengine/bevy/blob/dfe969005264fff54060f9fb148639f80f9cfb29/crates/bevy_reflect/src/list.rs#L309-L311) and [map](https://github.com/bevyengine/bevy/blob/dfe969005264fff54060f9fb148639f80f9cfb29/crates/bevy_reflect/src/map.rs#L361-L363) to return `None` when comparison couldn't be performed.
- [x] Updated docs comments to reflect above changes.

crates/bevy_reflect/src/array.rs

@@ -327,13 +327,16 @@ pub fn array_apply<A: Array>(array: &mut A, reflect: &dyn Reflect) {
 
 /// Compares two [arrays](Array) (one concrete and one reflected) to see if they
 /// are equal.
+///
+/// Returns [`None`] if the comparison couldn't even be performed.
 #[inline]
 pub fn array_partial_eq<A: Array>(array: &A, reflect: &dyn Reflect) -> Option<bool> {
     match reflect.reflect_ref() {
         ReflectRef::Array(reflect_array) if reflect_array.len() == array.len() => {
             for (a, b) in array.iter().zip(reflect_array.iter()) {
-                if let Some(false) | None = a.reflect_partial_eq(b) {
-                    return Some(false);
+                let eq_result = a.reflect_partial_eq(b);
+                if let failed @ (Some(false) | None) = eq_result {
+                    return failed;
                 }
             }
         }

crates/bevy_reflect/src/list.rs

@@ -293,6 +293,8 @@ pub fn list_apply<L: List>(a: &mut L, b: &dyn Reflect) {
 /// - `b` is a list;
 /// - `b` is the same length as `a`;
 /// - [`Reflect::reflect_partial_eq`] returns `Some(true)` for pairwise elements of `a` and `b`.
+///
+/// Returns [`None`] if the comparison couldn't even be performed.
 #[inline]
 pub fn list_partial_eq<L: List>(a: &L, b: &dyn Reflect) -> Option<bool> {
     let list = if let ReflectRef::List(list) = b.reflect_ref() {
@@ -306,8 +308,9 @@ pub fn list_partial_eq<L: List>(a: &L, b: &dyn Reflect) -> Option<bool> {
     }
 
     for (a_value, b_value) in a.iter().zip(list.iter()) {
-        if let Some(false) | None = a_value.reflect_partial_eq(b_value) {
-            return Some(false);
+        let eq_result = a_value.reflect_partial_eq(b_value);
+        if let failed @ (Some(false) | None) = eq_result {
+            return failed;
         }
     }
 

crates/bevy_reflect/src/map.rs

@@ -344,6 +344,8 @@ impl<'a> ExactSizeIterator for MapIter<'a> {}
 /// - `b` is the same length as `a`;
 /// - For each key-value pair in `a`, `b` contains a value for the given key,
 ///   and [`Reflect::reflect_partial_eq`] returns `Some(true)` for the two values.
+///
+/// Returns [`None`] if the comparison couldn't even be performed.
 #[inline]
 pub fn map_partial_eq<M: Map>(a: &M, b: &dyn Reflect) -> Option<bool> {
     let map = if let ReflectRef::Map(map) = b.reflect_ref() {
@@ -358,8 +360,9 @@ pub fn map_partial_eq<M: Map>(a: &M, b: &dyn Reflect) -> Option<bool> {
 
     for (key, value) in a.iter() {
         if let Some(map_value) = map.get(key) {
-            if let Some(false) | None = value.reflect_partial_eq(map_value) {
-                return Some(false);
+            let eq_result = value.reflect_partial_eq(map_value);
+            if let failed @ (Some(false) | None) = eq_result {
+                return failed;
             }
         } else {
             return Some(false);

crates/bevy_reflect/src/struct_trait.rs

@@ -437,6 +437,8 @@ impl Typed for DynamicStruct {
 /// - For each field in `a`, `b` contains a field with the same name and
 ///   [`Reflect::reflect_partial_eq`] returns `Some(true)` for the two field
 ///   values.
+///
+/// Returns [`None`] if the comparison couldn't even be performed.
 #[inline]
 pub fn struct_partial_eq<S: Struct>(a: &S, b: &dyn Reflect) -> Option<bool> {
     let struct_value = if let ReflectRef::Struct(struct_value) = b.reflect_ref() {
@@ -452,8 +454,9 @@ pub fn struct_partial_eq<S: Struct>(a: &S, b: &dyn Reflect) -> Option<bool> {
     for (i, value) in struct_value.iter_fields().enumerate() {
         let name = struct_value.name_at(i).unwrap();
         if let Some(field_value) = a.field(name) {
-            if let Some(false) | None = field_value.reflect_partial_eq(value) {
-                return Some(false);
+            let eq_result = field_value.reflect_partial_eq(value);
+            if let failed @ (Some(false) | None) = eq_result {
+                return failed;
             }
         } else {
             return Some(false);

crates/bevy_reflect/src/tuple.rs

@@ -369,6 +369,8 @@ pub fn tuple_apply<T: Tuple>(a: &mut T, b: &dyn Reflect) {
 /// - `b` is a tuple;
 /// - `b` has the same number of elements as `a`;
 /// - [`Reflect::reflect_partial_eq`] returns `Some(true)` for pairwise elements of `a` and `b`.
+///
+/// Returns [`None`] if the comparison couldn't even be performed.
 #[inline]
 pub fn tuple_partial_eq<T: Tuple>(a: &T, b: &dyn Reflect) -> Option<bool> {
     let b = if let ReflectRef::Tuple(tuple) = b.reflect_ref() {
@@ -382,9 +384,9 @@ pub fn tuple_partial_eq<T: Tuple>(a: &T, b: &dyn Reflect) -> Option<bool> {
     }
 
     for (a_field, b_field) in a.iter_fields().zip(b.iter_fields()) {
-        match a_field.reflect_partial_eq(b_field) {
-            Some(false) | None => return Some(false),
-            Some(true) => {}
+        let eq_result = a_field.reflect_partial_eq(b_field);
+        if let failed @ (Some(false) | None) = eq_result {
+            return failed;
         }
     }
 

crates/bevy_reflect/src/tuple_struct.rs

@@ -349,6 +349,8 @@ impl Typed for DynamicTupleStruct {
 /// - `b` is a tuple struct;
 /// - `b` has the same number of fields as `a`;
 /// - [`Reflect::reflect_partial_eq`] returns `Some(true)` for pairwise fields of `a` and `b`.
+///
+/// Returns [`None`] if the comparison couldn't even be performed.
 #[inline]
 pub fn tuple_struct_partial_eq<S: TupleStruct>(a: &S, b: &dyn Reflect) -> Option<bool> {
     let tuple_struct = if let ReflectRef::TupleStruct(tuple_struct) = b.reflect_ref() {
@@ -363,8 +365,9 @@ pub fn tuple_struct_partial_eq<S: TupleStruct>(a: &S, b: &dyn Reflect) -> Option
 
     for (i, value) in tuple_struct.iter_fields().enumerate() {
         if let Some(field_value) = a.field(i) {
-            if let Some(false) | None = field_value.reflect_partial_eq(value) {
-                return Some(false);
+            let eq_result = field_value.reflect_partial_eq(value);
+            if let failed @ (Some(false) | None) = eq_result {
+                return failed;
             }
         } else {
             return Some(false);