diff --git a/src/io/buf_read/mod.rs b/src/io/buf_read/mod.rs
index 7a0ecc60..3ee6e30b 100644
--- a/src/io/buf_read/mod.rs
+++ b/src/io/buf_read/mod.rs
@@ -124,7 +124,7 @@ extension_trait! {
             &'a mut self,
             byte: u8,
             buf: &'a mut Vec<u8>,
-        ) -> impl Future<Output = usize> + 'a [ReadUntilFuture<'a, Self>]
+        ) -> impl Future<Output = usize> [ReadUntilFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -177,7 +177,7 @@ extension_trait! {
         fn read_line<'a>(
             &'a mut self,
             buf: &'a mut String,
-        ) -> impl Future<Output = io::Result<usize>> + 'a [ReadLineFuture<'a, Self>]
+        ) -> impl Future<Output = io::Result<usize>> [ReadLineFuture<'a, Self>]
         where
             Self: Unpin,
         {
diff --git a/src/io/read/mod.rs b/src/io/read/mod.rs
index 388237c8..c8f4e28b 100644
--- a/src/io/read/mod.rs
+++ b/src/io/read/mod.rs
@@ -112,7 +112,7 @@ extension_trait! {
         fn read<'a>(
             &'a mut self,
             buf: &'a mut [u8],
-        ) -> impl Future<Output = io::Result<usize>> + 'a [ReadFuture<'a, Self>]
+        ) -> impl Future<Output = io::Result<usize>> [ReadFuture<'a, Self>]
         where
             Self: Unpin
         {
@@ -134,7 +134,7 @@ extension_trait! {
         fn read_vectored<'a>(
             &'a mut self,
             bufs: &'a mut [IoSliceMut<'a>],
-        ) -> impl Future<Output = io::Result<usize>> + 'a [ReadVectoredFuture<'a, Self>]
+        ) -> impl Future<Output = io::Result<usize>> [ReadVectoredFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -171,7 +171,7 @@ extension_trait! {
         fn read_to_end<'a>(
             &'a mut self,
             buf: &'a mut Vec<u8>,
-        ) -> impl Future<Output = io::Result<usize>> + 'a [ReadToEndFuture<'a, Self>]
+        ) -> impl Future<Output = io::Result<usize>> [ReadToEndFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -210,7 +210,7 @@ extension_trait! {
         fn read_to_string<'a>(
             &'a mut self,
             buf: &'a mut String,
-        ) -> impl Future<Output = io::Result<usize>> + 'a [ReadToStringFuture<'a, Self>]
+        ) -> impl Future<Output = io::Result<usize>> [ReadToStringFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -265,7 +265,7 @@ extension_trait! {
         fn read_exact<'a>(
             &'a mut self,
             buf: &'a mut [u8],
-        ) -> impl Future<Output = io::Result<()>> + 'a [ReadExactFuture<'a, Self>]
+        ) -> impl Future<Output = io::Result<()>> [ReadExactFuture<'a, Self>]
         where
             Self: Unpin,
         {
diff --git a/src/io/seek/mod.rs b/src/io/seek/mod.rs
index f565ca46..3b5036c8 100644
--- a/src/io/seek/mod.rs
+++ b/src/io/seek/mod.rs
@@ -76,7 +76,7 @@ extension_trait! {
         fn seek(
             &mut self,
             pos: SeekFrom,
-        ) -> impl Future<Output = io::Result<u64>> + '_ [SeekFuture<'_, Self>]
+        ) -> impl Future<Output = io::Result<u64>> [SeekFuture<'_, Self>]
         where
             Self: Unpin,
         {
diff --git a/src/io/write/mod.rs b/src/io/write/mod.rs
index 0ed91dda..3dee9feb 100644
--- a/src/io/write/mod.rs
+++ b/src/io/write/mod.rs
@@ -110,7 +110,7 @@ extension_trait! {
         fn write<'a>(
             &'a mut self,
             buf: &'a [u8],
-        ) -> impl Future<Output = io::Result<usize>> + 'a [WriteFuture<'a, Self>]
+        ) -> impl Future<Output = io::Result<usize>> [WriteFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -136,7 +136,7 @@ extension_trait! {
             # Ok(()) }) }
             ```
         "#]
-        fn flush(&mut self) -> impl Future<Output = io::Result<()>> + '_ [FlushFuture<'_, Self>]
+        fn flush(&mut self) -> impl Future<Output = io::Result<()>> [FlushFuture<'_, Self>]
         where
             Self: Unpin,
         {
@@ -158,7 +158,7 @@ extension_trait! {
         fn write_vectored<'a>(
             &'a mut self,
             bufs: &'a [IoSlice<'a>],
-        ) -> impl Future<Output = io::Result<usize>> + 'a [WriteVectoredFuture<'a, Self>]
+        ) -> impl Future<Output = io::Result<usize>> [WriteVectoredFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -194,7 +194,7 @@ extension_trait! {
         fn write_all<'a>(
             &'a mut self,
             buf: &'a [u8],
-        ) -> impl Future<Output = io::Result<()>> + 'a [WriteAllFuture<'a, Self>]
+        ) -> impl Future<Output = io::Result<()>> [WriteAllFuture<'a, Self>]
         where
             Self: Unpin,
         {
@@ -231,7 +231,7 @@ extension_trait! {
         fn write_fmt<'a>(
             &'a mut self,
             fmt: std::fmt::Arguments<'_>,
-        ) -> impl Future<Output = io::Result<()>> + 'a [WriteFmtFuture<'a, Self>]
+        ) -> impl Future<Output = io::Result<()>> [WriteFmtFuture<'a, Self>]
         where
             Self: Unpin,
         {
diff --git a/src/stream/stream/mod.rs b/src/stream/stream/mod.rs
index 4e074a2f..af7407a2 100644
--- a/src/stream/stream/mod.rs
+++ b/src/stream/stream/mod.rs
@@ -260,7 +260,7 @@ extension_trait! {
             # }) }
             ```
         "#]
-        fn next(&mut self) -> impl Future<Output = Option<Self::Item>> + '_ [NextFuture<'_, Self>]
+        fn next(&mut self) -> impl Future<Output = Option<Self::Item>> [NextFuture<'_, Self>]
         where
             Self: Unpin,
         {
@@ -1165,7 +1165,7 @@ extension_trait! {
         fn nth(
             &mut self,
             n: usize,
-        ) -> impl Future<Output = Option<Self::Item>> + '_ [NthFuture<'_, Self>]
+        ) -> impl Future<Output = Option<Self::Item>> [NthFuture<'_, Self>]
         where
             Self: Unpin + Sized,
         {
@@ -1221,7 +1221,7 @@ extension_trait! {
         fn all<F>(
             &mut self,
             f: F,
-        ) -> impl Future<Output = bool> + '_ [AllFuture<'_, Self, F, Self::Item>]
+        ) -> impl Future<Output = bool> [AllFuture<'_, Self, F, Self::Item>]
         where
             Self: Unpin + Sized,
             F: FnMut(Self::Item) -> bool,
@@ -1270,7 +1270,7 @@ extension_trait! {
         fn find<P>(
             &mut self,
             p: P,
-        ) -> impl Future<Output = Option<Self::Item>> + '_ [FindFuture<'_, Self, P>]
+        ) -> impl Future<Output = Option<Self::Item>> [FindFuture<'_, Self, P>]
         where
             Self: Unpin + Sized,
             P: FnMut(&Self::Item) -> bool,
@@ -1298,7 +1298,7 @@ extension_trait! {
         fn find_map<F, B>(
             &mut self,
             f: F,
-        ) -> impl Future<Output = Option<B>> + '_ [FindMapFuture<'_, Self, F>]
+        ) -> impl Future<Output = Option<B>> [FindMapFuture<'_, Self, F>]
         where
             Self: Unpin + Sized,
             F: FnMut(Self::Item) -> Option<B>,
@@ -1461,7 +1461,7 @@ extension_trait! {
         fn any<F>(
             &mut self,
             f: F,
-        ) -> impl Future<Output = bool> + '_ [AnyFuture<'_, Self, F, Self::Item>]
+        ) -> impl Future<Output = bool> [AnyFuture<'_, Self, F, Self::Item>]
         where
             Self: Unpin + Sized,
             F: FnMut(Self::Item) -> bool,
@@ -1697,7 +1697,7 @@ extension_trait! {
             &mut self,
             init: T,
             f: F,
-        ) -> impl Future<Output = Result<T, E>> + '_ [TryFoldFuture<'_, Self, F, T>]
+        ) -> impl Future<Output = Result<T, E>> [TryFoldFuture<'_, Self, F, T>]
         where
             Self: Unpin + Sized,
             F: FnMut(B, Self::Item) -> Result<T, E>,
@@ -1742,7 +1742,7 @@ extension_trait! {
         fn try_for_each<F, E>(
             &mut self,
             f: F,
-        ) -> impl Future<Output = E> + 'a [TryForEachFuture<'_, Self, F>]
+        ) -> impl Future<Output = E> [TryForEachFuture<'_, Self, F>]
         where
             Self: Unpin + Sized,
             F: FnMut(Self::Item) -> Result<(), E>,
@@ -1888,7 +1888,7 @@ extension_trait! {
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
         fn collect<'a, B>(
             self,
-        ) -> impl Future<Output = B> + 'a [Pin<Box<dyn Future<Output = B> + 'a + Send>>]
+        ) -> impl Future<Output = B> [Pin<Box<dyn Future<Output = B> + 'a + Send>>]
         where
             Self: Sized + 'a + Send,
             B: FromStream<Self::Item>,
@@ -2002,7 +2002,7 @@ extension_trait! {
         fn position<P>(
            &mut self,
            predicate: P,
-        ) -> impl Future<Output = Option<usize>> + '_ [PositionFuture<'_, Self, P>]
+        ) -> impl Future<Output = Option<usize>> [PositionFuture<'_, Self, P>]
         where
             Self: Unpin + Sized,
             P: FnMut(Self::Item) -> bool,
@@ -2335,7 +2335,7 @@ extension_trait! {
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
         fn sum<'a, S>(
             self,
-        ) -> impl Future<Output = S> + 'a [Pin<Box<dyn Future<Output = S> + 'a>>]
+        ) -> impl Future<Output = S> [Pin<Box<dyn Future<Output = S> + 'a>>]
         where
             Self: Sized + Stream<Item = S> + 'a,
             S: Sum<Self::Item>,
@@ -2381,7 +2381,7 @@ extension_trait! {
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
         fn product<'a, P>(
             self,
-        ) -> impl Future<Output = P> + 'a [Pin<Box<dyn Future<Output = P> + 'a>>]
+        ) -> impl Future<Output = P> [Pin<Box<dyn Future<Output = P> + 'a>>]
         where
             Self: Sized + Stream<Item = P> + 'a,
             P: Product,
diff --git a/src/utils.rs b/src/utils.rs
index 6ae49115..88731d28 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -302,10 +302,10 @@ macro_rules! extension_trait {
     };
 
     // Parse the return type in an extension method.
-    (@doc [-> impl Future<Output = $out:ty> $(+ $lt:lifetime)? [$f:ty] $($tail:tt)*] -> [$($accum:tt)*]) => {
+    (@doc [-> impl Future<Output = $out:ty> [$f:ty] $($tail:tt)*] -> [$($accum:tt)*]) => {
         extension_trait!(@doc [$($tail)*] -> [$($accum)* -> owned::ImplFuture<$out>]);
     };
-    (@ext [-> impl Future<Output = $out:ty> $(+ $lt:lifetime)? [$f:ty] $($tail:tt)*] -> [$($accum:tt)*]) => {
+    (@ext [-> impl Future<Output = $out:ty> [$f:ty] $($tail:tt)*] -> [$($accum:tt)*]) => {
         extension_trait!(@ext [$($tail)*] -> [$($accum)* -> $f]);
     };