erased_serde/
macros.rs

1/// Implement `serde::Serialize` for a trait object that has
2/// `erased_serde::Serialize` as a supertrait.
3///
4/// ```
5/// use erased_serde::serialize_trait_object;
6///
7/// trait Event: erased_serde::Serialize {
8///     /* ... */
9/// }
10///
11/// erased_serde::serialize_trait_object!(Event);
12/// ```
13///
14/// The macro supports traits that have type parameters and/or `where` clauses.
15///
16/// ```
17/// # use erased_serde::serialize_trait_object;
18/// #
19/// trait Difficult<T>: erased_serde::Serialize where T: Copy {
20///     /* ... */
21/// }
22///
23/// serialize_trait_object!(<T> Difficult<T> where T: Copy);
24/// ```
25#[macro_export]
26macro_rules! serialize_trait_object {
27    ($($path:tt)+) => {
28        $crate::__internal_serialize_trait_object!(begin $($path)+);
29    };
30}
31
32#[doc(hidden)]
33#[macro_export]
34macro_rules! __internal_serialize_trait_object {
35    // Invocation started with `<`, parse generics.
36    (begin < $($rest:tt)*) => {
37        $crate::__internal_serialize_trait_object!(generics () () $($rest)*);
38    };
39
40    // Invocation did not start with `<`.
41    (begin $first:tt $($rest:tt)*) => {
42        $crate::__internal_serialize_trait_object!(path () ($first) $($rest)*);
43    };
44
45    // End of generics with trailing comma.
46    (generics ($($generics:tt)*) () , > $($rest:tt)*) => {
47        $crate::__internal_serialize_trait_object!(path ($($generics)* ,) () $($rest)*);
48    };
49
50    // End of generics without trailing comma.
51    (generics ($($generics:tt)*) () > $($rest:tt)*) => {
52        $crate::__internal_serialize_trait_object!(path ($($generics)* ,) () $($rest)*);
53    };
54
55    // Generics open bracket.
56    (generics ($($generics:tt)*) ($($brackets:tt)*) < $($rest:tt)*) => {
57        $crate::__internal_serialize_trait_object!(generics ($($generics)* <) ($($brackets)* <) $($rest)*);
58    };
59
60    // Generics close bracket.
61    (generics ($($generics:tt)*) (< $($brackets:tt)*) > $($rest:tt)*) => {
62        $crate::__internal_serialize_trait_object!(generics ($($generics)* >) ($($brackets)*) $($rest)*);
63    };
64
65    // Token inside of generics.
66    (generics ($($generics:tt)*) ($($brackets:tt)*) $first:tt $($rest:tt)*) => {
67        $crate::__internal_serialize_trait_object!(generics ($($generics)* $first) ($($brackets)*) $($rest)*);
68    };
69
70    // End with `where` clause.
71    (path ($($generics:tt)*) ($($path:tt)*) where $($rest:tt)*) => {
72        $crate::__internal_serialize_trait_object!(sendsync ($($generics)*) ($($path)*) ($($rest)*));
73    };
74
75    // End without `where` clause.
76    (path ($($generics:tt)*) ($($path:tt)*)) => {
77        $crate::__internal_serialize_trait_object!(sendsync ($($generics)*) ($($path)*) ());
78    };
79
80    // Token inside of path.
81    (path ($($generics:tt)*) ($($path:tt)*) $first:tt $($rest:tt)*) => {
82        $crate::__internal_serialize_trait_object!(path ($($generics)*) ($($path)* $first) $($rest)*);
83    };
84
85    // Expand into four impls.
86    (sendsync ($($generics:tt)*) ($($path:tt)*) ($($bound:tt)*)) => {
87        $crate::__internal_serialize_trait_object!(impl ($($generics)*) ($($path)*) ($($bound)*) {
88            fn __check_erased_serialize_supertrait<$($generics)* __T>()
89            where
90                __T: ?$crate::__private::Sized + $($path)*,
91                $($bound)*
92            {
93                $crate::__private::require_erased_serialize_impl::<__T>();
94            }
95        });
96        $crate::__internal_serialize_trait_object!(impl ($($generics)*) ($($path)* + $crate::__private::Send) ($($bound)*));
97        $crate::__internal_serialize_trait_object!(impl ($($generics)*) ($($path)* + $crate::__private::Sync) ($($bound)*));
98        $crate::__internal_serialize_trait_object!(impl ($($generics)*) ($($path)* + $crate::__private::Send + $crate::__private::Sync) ($($bound)*));
99    };
100
101    // The impl.
102    (impl ($($generics:tt)*) ($($path:tt)*) ($($bound:tt)*) $({$($body:tt)*})*) => {
103        impl<'erased, $($generics)*> $crate::__private::serde::Serialize for dyn $($path)* + 'erased
104        where
105            $($bound)*
106        {
107            fn serialize<S>(&self, serializer: S) -> $crate::__private::Result<S::Ok, S::Error>
108            where
109                S: $crate::__private::serde::Serializer,
110            {
111                $($($body)*)*
112                $crate::serialize(self, serializer)
113            }
114        }
115    };
116}
117
118// TEST ////////////////////////////////////////////////////////////////////////
119
120#[cfg(test)]
121mod tests {
122    use crate::Serialize;
123
124    fn assert_serialize<T: ?Sized + serde::Serialize>() {}
125
126    #[test]
127    fn test_plain() {
128        trait Trait: Serialize {}
129
130        serialize_trait_object!(Trait);
131        assert_serialize::<dyn Trait>();
132        assert_serialize::<dyn Trait + Send>();
133    }
134
135    #[test]
136    fn test_type_parameter() {
137        trait Trait<T>: Serialize {}
138
139        serialize_trait_object!(<T> Trait<T>);
140        assert_serialize::<dyn Trait<u32>>();
141        assert_serialize::<dyn Trait<u32> + Send>();
142    }
143
144    #[test]
145    fn test_generic_bound() {
146        trait Trait<T: PartialEq<T>, U>: Serialize {}
147
148        serialize_trait_object!(<T: PartialEq<T>, U> Trait<T, U>);
149        assert_serialize::<dyn Trait<u32, ()>>();
150        assert_serialize::<dyn Trait<u32, ()> + Send>();
151    }
152
153    #[test]
154    fn test_where_clause() {
155        trait Trait<T>: Serialize
156        where
157            T: Clone,
158        {
159        }
160
161        serialize_trait_object!(<T> Trait<T> where T: Clone);
162        assert_serialize::<dyn Trait<u32>>();
163        assert_serialize::<dyn Trait<u32> + Send>();
164    }
165}
erased_serde/macros.rs

erased_serde/
macros.rs
