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// build-pass
fn main() {
let mut log_service = LogService { inner: Inner };
log_service.call(());
}
pub trait Service<Request> {
type Response;
fn call(&mut self, req: Request) -> Self::Response;
}
pub struct LogService<S> {
inner: S,
}
impl<T, U, S> Service<T> for LogService<S>
where
S: Service<T, Response = U>,
U: Extension + 'static,
for<'a> U::Item<'a>: std::fmt::Debug,
{
type Response = S::Response;
fn call(&mut self, req: T) -> Self::Response {
self.inner.call(req)
}
}
pub struct Inner;
impl Service<()> for Inner {
type Response = Resp;
fn call(&mut self, req: ()) -> Self::Response {
Resp::A(req)
}
}
pub trait Extension {
type Item<'a>;
fn touch<F>(self, f: F) -> Self
where
for<'a> F: Fn(Self::Item<'a>);
}
pub enum Resp {
A(()),
}
impl Extension for Resp {
type Item<'a> = RespItem<'a>;
fn touch<F>(self, _f: F) -> Self
where
for<'a> F: Fn(Self::Item<'a>),
{
match self {
Self::A(a) => Self::A(a),
}
}
}
pub enum RespItem<'a> {
A(&'a ()),
}
impl<'a> std::fmt::Debug for RespItem<'a> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
Self::A(arg0) => f.debug_tuple("A").field(arg0).finish(),
}
}
}
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