Derive serde Deserialize with generic constraint

I'm trying to create a struct like so:


pub struct MyStruct<T: Serialize + DeserializeOwned>
where
    T: 'static,
{
   pub field: Type,
...
pub generic_field:T
}

But I can't see how to satisfy the Deserialize. Rust emits this message:

type annotations needed: cannot satisfy `T: _::_serde::Deserialize<'de>`
cannot satisfy `T: _::_serde::Deserialize<'de>`

Here is part of output of the Deserializer derive from ra:

#[automatically_derived]
  impl < 'de,T:Serialize+DeserializeOwned>_serde::Deserialize< 'de>for MyStruct<T>where T: 'static,T:_serde::Deserialize< 'de>{
    fn deserialize<__D>(__deserializer:__D) -> _serde::__private::Result<Self,__D::Error>where __D:_serde::Deserializer< 'de> ,{
      #[allow(non_camel_case_types)]
      enum __Field {
        __field0,__field1,__field2,__field3,__field4,__field5,__field6,__ignore,
      }

The line it specifically complains at is:
''static,T:_serde::Deserialize< 'de>'

Any help would be appreciated!

I expect this has probably been asked before, but I have not been able to word it in a satisfactory for google to be of much help.

You can just remove the constraints, the derive will take care of it.

#[derive(Serialize, Deserialize)]
pub struct MyStruct<T>
where
    T: 'static,
{
   pub field: Type,
   pub generic_field: T,
}

In general, you don't need to add constraints to structs. You can just add the exact constraints you need to whatever functions or methods need them.

2 Likes

If you need to, you can add a #[serde(bound = "T: Serialize + DeserializeOwned")] attribute to MyStruct if you only want it to be deserialized under certain conditions.

use serde::{de::DeserializeOwned, Deserialize, Serialize};

#[derive(Serialize, Deserialize)]
#[serde(bound = "T: Serialize + DeserializeOwned")]
struct MyStruct<T: DeserializeOwned> {
    generic_field: T,
}

(playground)

1 Like

Thank you!

1 Like

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