tokio: use cfg-if to actually fix windows build

Author: Keruspe

Cargo.lock

@@ -21,6 +21,7 @@ tokio = ["dep:tokio", "dep:tokio-stream"]
 
 [dependencies]
 async-trait = "^0.1.89"
+cfg-if = "^1.0"
 futures-core = "^0.3"
 futures-io = "^0.3"
 

Cargo.toml

@@ -2,6 +2,7 @@
 
 use crate::{AsyncIOHandle, Executor, IOHandle, Reactor, Runtime, RuntimeKit, Task, sys::IO};
 use async_trait::async_trait;
+use cfg_if::cfg_if;
 use futures_core::Stream;
 use std::{
     future::Future,
@@ -117,14 +118,16 @@ impl Reactor for Tokio {
         socket: IOHandle<H>,
     ) -> io::Result<impl AsyncIOHandle + Send> {
         let _enter = self.handle().as_ref().map(|handle| handle.enter());
-        if cfg!(unix) {
-            Ok(Box::new(unix::AsyncFdWrapper(
-                tokio::io::unix::AsyncFd::new(socket)?,
-            )))
-        } else {
-            Err(io::Error::other(
-                "Registering FD on tokio reactor is only supported on unix",
-            ))
+        cfg_if! {
+            if #[cfg(unix)] {
+                Ok(Box::new(unix::AsyncFdWrapper(
+                    tokio::io::unix::AsyncFd::new(socket)?,
+                )))
+            } else {
+                Err(io::Error::other(
+                    "Registering FD on tokio reactor is only supported on unix",
+                ))
+            }
         }
     }