Warp::query with lifetime

I’m trying to do something like this:

let whatever = path!(String / "whatever")
    .map(|_, _| "");

pub struct WhateverQuery<'a> {
    x: &'a str,

When I run it like this, I get an error:

error[E0279]: the requirement `for<'de> 'de : ` is not satisfied (`expected bound lifetime parameter 'de, found concrete lifetime`)
  --> src/main.rs:29:14

    29 |         .and(warp::query::query::<WhateverQuery<'_>>())
       |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
       = note: required because of the requirements on the impl of `for<'de> _IMPL_DESERIALIZE_FOR_WhateverQuery::_serde::Deserialize<'de>` for `WhateverQuery<'_>`
       = note: required because of the requirements on the impl of `_IMPL_DESERIALIZE_FOR_WhateverQuery::_serde::de::DeserializeOwned` for `WhateverQuery<'_>`
       = note: required by `warp::query`

I’m honestly not sure what this error means, so I’ve just tried to replace the hidden lifetime parameter with a static one - for testing - when I ran into this issue:

error: internal compiler error: broken MIR in DefId(0/0:11 ~ app[df35]::main[0]) (NoSolution): could not prove Binder(TraitPredicate(<WhateverQuery<'_> as _IMPL_DESERIALIZE_FOR_WhateverQuery::_serde::de::DeserializeOwned>))

thread 'main' panicked at 'no errors encountered even though `delay_span_bug` issued', librustc_errors/lib.rs:313:17
note: Run with `RUST_BACKTRACE=1` for a backtrace.

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.30.0-nightly (73c78734b 2018-08-05) running on x86_64-unknown-linux-gnu

note: compiler flags: -C debuginfo=2 -C incremental --crate-type bin

note: some of the compiler flags provided by cargo are hidden

Could someone please explain what exactly the problem is and how could it be solved? Thanks!

I think Serde needs extra annotations if you want to make the result a temporary struct dependent on the input: https://serde.rs/lifetimes.html#borrowing-data-in-a-derived-impl