feat: to no_std future::ready

Author: k-nasa

src/future/ready.rs

@@ -1,3 +1,8 @@
+use core::future::Future;
+use core::pin::Pin;
+
+use crate::task::{Context, Poll};
+
 /// Resolves to the provided value.
 ///
 /// This function is an async version of [`std::convert::identity`].
@@ -15,6 +20,22 @@
 /// #
 /// # })
 /// ```
-pub async fn ready<T>(val: T) -> T {
-    val
+pub fn ready<T>(val: T) -> Ready<T> {
+    Ready(Some(val))
+}
+
+/// This future is constructed by the [`ready`] function.
+///
+/// [`ready`]: fn.ready.html
+#[derive(Debug)]
+pub struct Ready<T>(Option<T>);
+
+impl<T> Unpin for Ready<T> {}
+
+impl<T> Future for Ready<T> {
+    type Output = T;
+
+    fn poll(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<T> {
+        Poll::Ready(self.0.take().unwrap())
+    }
 }