Cannot derive Deserialize for a type that contains a type which contains a static reference

[shepmaster]

use serde::Deserialize; // 1.0.104

#[derive(Deserialize)]
pub struct Foo(&'static str);

#[derive(Deserialize)]
pub struct Bar(Foo);

error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'de` due to conflicting requirements
 --> src/lib.rs:7:16
  |
7 | pub struct Bar(Foo);
  |                ^^^
  |
note: first, the lifetime cannot outlive the lifetime `'de` as defined on the impl at 6:10...
 --> src/lib.rs:6:10
  |
6 | #[derive(Deserialize)]
  |          ^^^^^^^^^^^
  = note: ...so that the types are compatible:
          expected _IMPL_DESERIALIZE_FOR_Foo::_serde::Deserializer<'_>
             found _IMPL_DESERIALIZE_FOR_Foo::_serde::Deserializer<'de>
  = note: but, the lifetime must be valid for the static lifetime...
  = note: ...so that the types are compatible:
          expected _IMPL_DESERIALIZE_FOR_Foo::_serde::Deserialize<'_>
             found _IMPL_DESERIALIZE_FOR_Foo::_serde::Deserialize<'static>

error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'de` due to conflicting requirements
 --> src/lib.rs:7:16
  |
7 | pub struct Bar(Foo);
  |                ^^^
  |
note: first, the lifetime cannot outlive the lifetime `'de` as defined on the impl at 6:10...
 --> src/lib.rs:6:10
  |
6 | #[derive(Deserialize)]
  |          ^^^^^^^^^^^
  = note: ...so that the types are compatible:
          expected _IMPL_DESERIALIZE_FOR_Foo::_serde::de::SeqAccess<'_>
             found _IMPL_DESERIALIZE_FOR_Foo::_serde::de::SeqAccess<'de>
  = note: but, the lifetime must be valid for the static lifetime...
  = note: ...so that the types are compatible:
          expected _IMPL_DESERIALIZE_FOR_Foo::_serde::Deserialize<'_>
             found _IMPL_DESERIALIZE_FOR_Foo::_serde::Deserialize<'static>

Notably, #[serde(borrow)], as suggested by #1417, doesn't work:

use serde::Deserialize; // 1.0.104

#[derive(Deserialize)]
pub struct Foo(&'static str);

#[derive(Deserialize)]
pub struct Bar(#[serde(borrow = "'static")] Foo);

error: field `0` has no lifetimes to borrow
 --> src/lib.rs:7:16
  |
7 | pub struct Bar(#[serde(borrow = "'static")] Foo);
  |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Related, but seemingly different:

• DeserializedOwned doesn't work for structs with &'static refs? #1597

[dtolnay]

Foo's Deserialize impl looks like:

impl<'de> Deserialize<'de> for Foo
where
    'de: 'static

so that additional constraint would need to be provided on Bar's impl by a serde bound attribute.

use serde::Deserialize;

#[derive(Deserialize)]
pub struct Foo(&'static str);

#[derive(Deserialize)]
#[serde(bound(deserialize = "'de: 'static"))]
pub struct Bar(Foo);

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=c99fa29f3b2539cbba570eea4979d809

[bblum]

Sorry for thread necro, but I find that solution emits the warning "unnecessary lifetime parameter 'de ... you can use the 'static lifetime directly, in place of 'de".

Worse, due to rust-lang/rust#96956, the warning un-silenceable. Even #[allow(warnings)] doesn't work. Is there a way around this?

[LLFourn]

@bblum if you are desperate for a quick fix you can do:

#[derive(Deserialize, Debug)]
pub struct Bar(
    #[serde(bound(deserialize = "Foo: Deserialize<'de>"))]
    Foo
);