| /// Implement `serde::Serialize` for a trait object that has |
| /// `erased_serde::Serialize` as a supertrait. |
| /// |
| /// ``` |
| /// #[macro_use] |
| /// extern crate erased_serde; |
| /// |
| /// trait Event: erased_serde::Serialize { |
| /// /* ... */ |
| /// } |
| /// |
| /// serialize_trait_object!(Event); |
| /// # |
| /// # fn main() {} |
| /// ``` |
| /// |
| /// The macro supports traits that have type parameters and/or `where` clauses. |
| /// |
| /// ``` |
| /// # #[macro_use] |
| /// # extern crate erased_serde; |
| /// # |
| /// trait Difficult<T>: erased_serde::Serialize where T: Copy { |
| /// /* ... */ |
| /// } |
| /// |
| /// serialize_trait_object!(<T> Difficult<T> where T: Copy); |
| /// # |
| /// # fn main() {} |
| /// ``` |
| #[macro_export] |
| macro_rules! serialize_trait_object { |
| ($($path:tt)+) => { |
| __internal_serialize_trait_object!(begin $($path)+); |
| }; |
| } |
| |
| #[doc(hidden)] |
| #[macro_export] |
| macro_rules! __internal_serialize_trait_object { |
| // Invocation started with `<`, parse generics. |
| (begin < $($rest:tt)*) => { |
| __internal_serialize_trait_object!(generics () () $($rest)*); |
| }; |
| |
| // Invocation did not start with `<`. |
| (begin $first:tt $($rest:tt)*) => { |
| __internal_serialize_trait_object!(path () ($first) $($rest)*); |
| }; |
| |
| // End of generics. |
| (generics ($($generics:tt)*) () > $($rest:tt)*) => { |
| __internal_serialize_trait_object!(path ($($generics)*) () $($rest)*); |
| }; |
| |
| // Generics open bracket. |
| (generics ($($generics:tt)*) ($($brackets:tt)*) < $($rest:tt)*) => { |
| __internal_serialize_trait_object!(generics ($($generics)* <) ($($brackets)* <) $($rest)*); |
| }; |
| |
| // Generics close bracket. |
| (generics ($($generics:tt)*) (< $($brackets:tt)*) > $($rest:tt)*) => { |
| __internal_serialize_trait_object!(generics ($($generics)* >) ($($brackets)*) $($rest)*); |
| }; |
| |
| // Token inside of generics. |
| (generics ($($generics:tt)*) ($($brackets:tt)*) $first:tt $($rest:tt)*) => { |
| __internal_serialize_trait_object!(generics ($($generics)* $first) ($($brackets)*) $($rest)*); |
| }; |
| |
| // End with `where` clause. |
| (path ($($generics:tt)*) ($($path:tt)*) where $($rest:tt)*) => { |
| __internal_serialize_trait_object!(sendsync ($($generics)*) ($($path)*) ($($rest)*)); |
| }; |
| |
| // End without `where` clause. |
| (path ($($generics:tt)*) ($($path:tt)*)) => { |
| __internal_serialize_trait_object!(sendsync ($($generics)*) ($($path)*) ()); |
| }; |
| |
| // Token inside of path. |
| (path ($($generics:tt)*) ($($path:tt)*) $first:tt $($rest:tt)*) => { |
| __internal_serialize_trait_object!(path ($($generics)*) ($($path)* $first) $($rest)*); |
| }; |
| |
| // Expand into four impls. |
| (sendsync ($($generics:tt)*) ($($path:tt)*) ($($bound:tt)*)) => { |
| __internal_serialize_trait_object!(impl ($($generics)*) ($($path)*) ($($bound)*)); |
| __internal_serialize_trait_object!(impl ($($generics)*) ($($path)* + $crate::private::Send) ($($bound)*)); |
| __internal_serialize_trait_object!(impl ($($generics)*) ($($path)* + $crate::private::Sync) ($($bound)*)); |
| __internal_serialize_trait_object!(impl ($($generics)*) ($($path)* + $crate::private::Send + $crate::private::Sync) ($($bound)*)); |
| }; |
| |
| // The impl. |
| (impl ($($generics:tt)*) ($($path:tt)*) ($($bound:tt)*)) => { |
| impl<'erased, $($generics)*> $crate::private::serde::Serialize for $($path)* + 'erased where $($bound)* { |
| fn serialize<S>(&self, serializer: S) -> $crate::private::Result<S::Ok, S::Error> where S: $crate::private::serde::Serializer { |
| $crate::serialize(self, serializer) |
| } |
| } |
| }; |
| } |
| |
| // TEST //////////////////////////////////////////////////////////////////////// |
| |
| #[cfg(test)] |
| mod tests { |
| use serde; |
| use Serialize; |
| |
| fn assert_serialize<T: ?Sized + serde::Serialize>() {} |
| |
| #[test] |
| fn test_plain() { |
| trait Trait: Serialize {} |
| |
| serialize_trait_object!(Trait); |
| assert_serialize::<Trait>(); |
| assert_serialize::<Trait + Send>(); |
| } |
| |
| #[test] |
| fn test_type_parameter() { |
| trait Trait<T>: Serialize {} |
| |
| serialize_trait_object!(<T> Trait<T>); |
| assert_serialize::<Trait<u32>>(); |
| assert_serialize::<Trait<u32> + Send>(); |
| } |
| |
| #[test] |
| fn test_generic_bound() { |
| trait Trait<T: PartialEq<T>, U>: Serialize {} |
| |
| serialize_trait_object!(<T: PartialEq<T>, U> Trait<T, U>); |
| assert_serialize::<Trait<u32, ()>>(); |
| assert_serialize::<Trait<u32, ()> + Send>(); |
| } |
| |
| #[test] |
| fn test_where_clause() { |
| trait Trait<T>: Serialize where T: Clone {} |
| |
| serialize_trait_object!(<T> Trait<T> where T: Clone); |
| assert_serialize::<Trait<u32>>(); |
| assert_serialize::<Trait<u32> + Send>(); |
| } |
| } |