Remove unnecessary types in extension_trait.

The remaining type requires the square brackets (for now) because a `ty`
cannot immediately precede a `$(tt)*`.

Author: nnethercote

src/future/future/mod.rs

@@ -45,7 +45,7 @@ extension_trait! {
         /// ```
         #[cfg(feature = "unstable")]
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
-        fn delay(self, dur: Duration) -> impl Future<Output = Self::Output> [DelayFuture<Self>]
+        fn delay(self, dur: Duration) -> [DelayFuture<Self>]
         where
             Self: Sized,
         {
@@ -70,8 +70,7 @@ extension_trait! {
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
         fn flatten(
             self,
-        ) -> impl Future<Output = <Self::Output as IntoFuture>::Output>
-            [FlattenFuture<Self, <Self::Output as IntoFuture>::Future>]
+        ) -> [FlattenFuture<Self, <Self::Output as IntoFuture>::Future>]
         where
             Self: Sized,
             <Self as Future>::Output: IntoFuture,
@@ -113,7 +112,7 @@ extension_trait! {
         fn race<F>(
             self,
             other: F,
-        ) -> impl Future<Output = <Self as std::future::Future>::Output> [Race<Self, F>]
+        ) -> [Race<Self, F>]
         where
             Self: std::future::Future + Sized,
             F: std::future::Future<Output = <Self as std::future::Future>::Output>,
@@ -159,7 +158,7 @@ extension_trait! {
         fn try_race<F, T, E>(
             self,
             other: F
-        ) -> impl Future<Output = <Self as std::future::Future>::Output> [TryRace<Self, F>]
+        ) -> [TryRace<Self, F>]
         where
             Self: std::future::Future<Output = Result<T, E>> + Sized,
             F: std::future::Future<Output = <Self as std::future::Future>::Output>,
@@ -196,7 +195,7 @@ extension_trait! {
         fn join<F>(
             self,
             other: F
-        ) -> impl Future<Output = (<Self as std::future::Future>::Output, <F as std::future::Future>::Output)> [Join<Self, F>]
+        ) -> [Join<Self, F>]
         where
             Self: std::future::Future + Sized,
             F: std::future::Future,
@@ -243,7 +242,7 @@ extension_trait! {
         fn try_join<F, A, B, E>(
             self,
             other: F
-        ) -> impl Future<Output = Result<(A, B), E>> [TryJoin<Self, F>]
+        ) -> [TryJoin<Self, F>]
         where
             Self: std::future::Future<Output = Result<A, E>> + Sized,
             F: std::future::Future<Output = Result<B, E>>,
@@ -279,7 +278,7 @@ extension_trait! {
         "#]
         #[cfg(any(all(feature = "default", feature = "unstable"), feature = "docs"))]
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
-        fn timeout(self, dur: Duration) -> impl Future<Output = Self::Output> [TimeoutFuture<Self>]
+        fn timeout(self, dur: Duration) -> [TimeoutFuture<Self>]
             where Self: Sized
         {
             TimeoutFuture::new(self, dur)

src/io/buf_read/mod.rs

@@ -78,7 +78,7 @@ extension_trait! {
             &'a mut self,
             byte: u8,
             buf: &'a mut Vec<u8>,
-        ) -> impl Future<Output = usize> [ReadUntilFuture<'a, Self>]
+        ) -> [ReadUntilFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -131,7 +131,7 @@ extension_trait! {
         fn read_line<'a>(
             &'a mut self,
             buf: &'a mut String,
-        ) -> impl Future<Output = io::Result<usize>> [ReadLineFuture<'a, Self>]
+        ) -> [ReadLineFuture<'a, Self>]
         where
             Self: Unpin,
         {

src/io/read/mod.rs

@@ -64,7 +64,7 @@ extension_trait! {
         fn read<'a>(
             &'a mut self,
             buf: &'a mut [u8],
-        ) -> impl Future<Output = io::Result<usize>> [ReadFuture<'a, Self>]
+        ) -> [ReadFuture<'a, Self>]
         where
             Self: Unpin
         {
@@ -86,7 +86,7 @@ extension_trait! {
         fn read_vectored<'a>(
             &'a mut self,
             bufs: &'a mut [IoSliceMut<'a>],
-        ) -> impl Future<Output = io::Result<usize>> [ReadVectoredFuture<'a, Self>]
+        ) -> [ReadVectoredFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -123,7 +123,7 @@ extension_trait! {
         fn read_to_end<'a>(
             &'a mut self,
             buf: &'a mut Vec<u8>,
-        ) -> impl Future<Output = io::Result<usize>> [ReadToEndFuture<'a, Self>]
+        ) -> [ReadToEndFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -162,7 +162,7 @@ extension_trait! {
         fn read_to_string<'a>(
             &'a mut self,
             buf: &'a mut String,
-        ) -> impl Future<Output = io::Result<usize>> [ReadToStringFuture<'a, Self>]
+        ) -> [ReadToStringFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -217,7 +217,7 @@ extension_trait! {
         fn read_exact<'a>(
             &'a mut self,
             buf: &'a mut [u8],
-        ) -> impl Future<Output = io::Result<()>> [ReadExactFuture<'a, Self>]
+        ) -> [ReadExactFuture<'a, Self>]
         where
             Self: Unpin,
         {

src/io/seek/mod.rs

@@ -40,7 +40,7 @@ extension_trait! {
         fn seek(
             &mut self,
             pos: SeekFrom,
-        ) -> impl Future<Output = io::Result<u64>> [SeekFuture<'_, Self>]
+        ) -> [SeekFuture<'_, Self>]
         where
             Self: Unpin,
         {

src/io/write/mod.rs

@@ -49,7 +49,7 @@ extension_trait! {
         fn write<'a>(
             &'a mut self,
             buf: &'a [u8],
-        ) -> impl Future<Output = io::Result<usize>> [WriteFuture<'a, Self>]
+        ) -> [WriteFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -75,7 +75,7 @@ extension_trait! {
             # Ok(()) }) }
             ```
         "#]
-        fn flush(&mut self) -> impl Future<Output = io::Result<()>> [FlushFuture<'_, Self>]
+        fn flush(&mut self) -> [FlushFuture<'_, Self>]
         where
             Self: Unpin,
         {
@@ -97,7 +97,7 @@ extension_trait! {
         fn write_vectored<'a>(
             &'a mut self,
             bufs: &'a [IoSlice<'a>],
-        ) -> impl Future<Output = io::Result<usize>> [WriteVectoredFuture<'a, Self>]
+        ) -> [WriteVectoredFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -133,7 +133,7 @@ extension_trait! {
         fn write_all<'a>(
             &'a mut self,
             buf: &'a [u8],
-        ) -> impl Future<Output = io::Result<()>> [WriteAllFuture<'a, Self>]
+        ) -> [WriteAllFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -170,7 +170,7 @@ extension_trait! {
         fn write_fmt<'a>(
             &'a mut self,
             fmt: std::fmt::Arguments<'_>,
-        ) -> impl Future<Output = io::Result<()>> [WriteFmtFuture<'a, Self>]
+        ) -> [WriteFmtFuture<'a, Self>]
         where
             Self: Unpin,
         {