Make WriteFmtFuture must_use
Fixes Thanks to for pointing out the location of the issue.
@@ -6,6 +6,7 @@ use crate::task::{Context, Poll};
#[doc(hidden)]
#[allow(missing_debug_implementations)]
+#[must_use]
pub struct WriteFmtFuture<'a, T: Unpin + ?Sized> {
pub(crate) writer: &'a mut T,
pub(crate) res: Option<io::Result<Vec<u8>>>,
