use auto-enums instead of hand-rolling the future

tokio-epoll-uring/Cargo.toml

@@ -8,6 +8,7 @@ repository = "https://github.com/neondatabase/tokio-epoll-uring"
 license = "MIT OR Apache-2.0"
 
 [dependencies]
+auto_enums = "0.8.2"
 futures = "0.3.28"
 io-uring = "0.6.0"
 once_cell = "1.18.0"

tokio-epoll-uring/src/system/submission/op_fut.rs

@@ -1,4 +1,4 @@
-use std::{fmt::Display, pin::Pin, sync::Arc};
+use std::{fmt::Display, sync::Arc};
 
 /// An io_uring operation and the resources it operates on.
 ///
@@ -156,42 +156,11 @@ where
 }
 
 // Used by `execute_op` to avoid boxing the future returned by the `with_submit_side` closure.
-enum Fut<Output, A, B, C, D, E>
-where
-    A: std::future::Future<Output = Output>,
-    B: std::future::Future<Output = Output>,
-    C: std::future::Future<Output = Output>,
-    D: std::future::Future<Output = Output>,
-    E: std::future::Future<Output = Output>,
-{
+#[auto_enums::enum_derive(Future)]
+enum Fut<A, B, C, D, E> {
     A(A),
     B(B),
     C(C),
     D(D),
     E(E),
 }
-impl<Output, A, B, C, D, E> std::future::Future for Fut<Output, A, B, C, D, E>
-where
-    A: std::future::Future<Output = Output>,
-    B: std::future::Future<Output = Output>,
-    C: std::future::Future<Output = Output>,
-    D: std::future::Future<Output = Output>,
-    E: std::future::Future<Output = Output>,
-{
-    type Output = Output;
-
-    fn poll(
-        self: std::pin::Pin<&mut Self>,
-        cx: &mut std::task::Context<'_>,
-    ) -> std::task::Poll<Self::Output> {
-        unsafe {
-            match self.get_unchecked_mut() {
-                Self::A(x) => Pin::new_unchecked(x).poll(cx),
-                Self::B(x) => Pin::new_unchecked(x).poll(cx),
-                Self::C(x) => Pin::new_unchecked(x).poll(cx),
-                Self::D(x) => Pin::new_unchecked(x).poll(cx),
-                Self::E(x) => Pin::new_unchecked(x).poll(cx),
-            }
-        }
-    }
-}