Make generated enums derive(Hash) to allow them to be used in collect…

…ions like HashSet or as keys in HashMaps.

PiperOrigin-RevId: 706837705

rust/test/shared/enum_test.rs

@@ -208,3 +208,15 @@ fn test_debug_string() {
         eq("TestEnumWithNumericNames::from(42)")
     );
 }
+
+#[gtest]
+fn test_enum_in_hash_set() {
+    use test_all_types::NestedEnum;
+    let mut s = std::collections::HashSet::<NestedEnum>::new();
+    s.insert(NestedEnum::Foo);
+    s.insert(NestedEnum::Bar);
+    s.insert(NestedEnum::try_from(1).unwrap()); // FOO = 1
+    assert_that!(s.len(), eq(2));
+    assert_that!(s.contains(&NestedEnum::Bar), eq(true));
+    assert_that!(s.contains(&NestedEnum::Baz), eq(false));
+}

src/google/protobuf/compiler/rust/enum.cc

@@ -224,7 +224,7 @@ void GenerateEnumDefinition(Context& ctx, const EnumDescriptor& desc) {
       },
       R"rs(
       #[repr(transparent)]
-      #[derive(Clone, Copy, PartialEq, Eq)]
+      #[derive(Clone, Copy, PartialEq, Eq, Hash)]
       pub struct $name$(i32);
 
       #[allow(non_upper_case_globals)]