diff --git a/src/future/future/mod.rs b/src/future/future/mod.rs
index e20f8bac..a244c285 100644
--- a/src/future/future/mod.rs
+++ b/src/future/future/mod.rs
@@ -22,7 +22,6 @@ cfg_unstable_default! {
 
 pub use core::future::Future as Future;
 
-extension_trait! {
     #[doc = r#"
         Extension methods for [`Future`].
 
@@ -45,7 +44,7 @@ extension_trait! {
         /// ```
         #[cfg(feature = "unstable")]
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
-        fn delay(self, dur: Duration) -> [DelayFuture<Self>]
+        fn delay(self, dur: Duration) -> DelayFuture<Self>
         where
             Self: Sized,
         {
@@ -70,7 +69,7 @@ extension_trait! {
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
         fn flatten(
             self,
-        ) -> [FlattenFuture<Self, <Self::Output as IntoFuture>::Future>]
+        ) -> FlattenFuture<Self, <Self::Output as IntoFuture>::Future>
         where
             Self: Sized,
             <Self as Future>::Output: IntoFuture,
@@ -112,7 +111,7 @@ extension_trait! {
         fn race<F>(
             self,
             other: F,
-        ) -> [Race<Self, F>]
+        ) -> Race<Self, F>
         where
             Self: std::future::Future + Sized,
             F: std::future::Future<Output = <Self as std::future::Future>::Output>,
@@ -158,7 +157,7 @@ extension_trait! {
         fn try_race<F, T, E>(
             self,
             other: F
-        ) -> [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>,
@@ -195,7 +194,7 @@ extension_trait! {
         fn join<F>(
             self,
             other: F
-        ) -> [Join<Self, F>]
+        ) -> Join<Self, F>
         where
             Self: std::future::Future + Sized,
             F: std::future::Future,
@@ -242,7 +241,7 @@ extension_trait! {
         fn try_join<F, A, B, E>(
             self,
             other: F
-        ) -> [TryJoin<Self, F>]
+        ) -> TryJoin<Self, F>
         where
             Self: std::future::Future<Output = Result<A, E>> + Sized,
             F: std::future::Future<Output = Result<B, E>>,
@@ -278,13 +277,12 @@ extension_trait! {
         "#]
         #[cfg(any(all(feature = "default", feature = "unstable"), feature = "docs"))]
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
-        fn timeout(self, dur: Duration) -> [TimeoutFuture<Self>]
+        fn timeout(self, dur: Duration) -> TimeoutFuture<Self>
             where Self: Sized
         {
             TimeoutFuture::new(self, dur)
         }
     }
-}
 
 impl<T: Future + ?Sized> FutureExt for T {}
 
diff --git a/src/io/buf_read/mod.rs b/src/io/buf_read/mod.rs
index 8f248e2b..f8bffaf3 100644
--- a/src/io/buf_read/mod.rs
+++ b/src/io/buf_read/mod.rs
@@ -17,7 +17,6 @@ use crate::task::{Context, Poll};
 
 pub use futures_io::AsyncBufRead as BufRead;
 
-extension_trait! {
     #[doc = r#"
         Extension methods for [`BufRead`].
 
@@ -78,7 +77,7 @@ extension_trait! {
             &'a mut self,
             byte: u8,
             buf: &'a mut Vec<u8>,
-        ) -> [ReadUntilFuture<'a, Self>]
+        ) -> ReadUntilFuture<'a, Self>
         where
             Self: Unpin,
         {
@@ -131,7 +130,7 @@ extension_trait! {
         fn read_line<'a>(
             &'a mut self,
             buf: &'a mut String,
-        ) -> [ReadLineFuture<'a, Self>]
+        ) -> ReadLineFuture<'a, Self>
         where
             Self: Unpin,
         {
@@ -237,7 +236,6 @@ extension_trait! {
             }
         }
     }
-}
 
 impl<T: BufRead + ?Sized> BufReadExt for T {}
 
diff --git a/src/io/read/mod.rs b/src/io/read/mod.rs
index f96b8154..0109a3ac 100644
--- a/src/io/read/mod.rs
+++ b/src/io/read/mod.rs
@@ -23,7 +23,6 @@ pub use take::Take;
 
 pub use futures_io::AsyncRead as Read;
 
-extension_trait! {
     #[doc = r#"
         Extension methods for [`Read`].
 
@@ -64,7 +63,7 @@ extension_trait! {
         fn read<'a>(
             &'a mut self,
             buf: &'a mut [u8],
-        ) -> [ReadFuture<'a, Self>]
+        ) -> ReadFuture<'a, Self>
         where
             Self: Unpin
         {
@@ -86,7 +85,7 @@ extension_trait! {
         fn read_vectored<'a>(
             &'a mut self,
             bufs: &'a mut [IoSliceMut<'a>],
-        ) -> [ReadVectoredFuture<'a, Self>]
+        ) -> ReadVectoredFuture<'a, Self>
         where
             Self: Unpin,
         {
@@ -123,7 +122,7 @@ extension_trait! {
         fn read_to_end<'a>(
             &'a mut self,
             buf: &'a mut Vec<u8>,
-        ) -> [ReadToEndFuture<'a, Self>]
+        ) -> ReadToEndFuture<'a, Self>
         where
             Self: Unpin,
         {
@@ -162,7 +161,7 @@ extension_trait! {
         fn read_to_string<'a>(
             &'a mut self,
             buf: &'a mut String,
-        ) -> [ReadToStringFuture<'a, Self>]
+        ) -> ReadToStringFuture<'a, Self>
         where
             Self: Unpin,
         {
@@ -217,7 +216,7 @@ extension_trait! {
         fn read_exact<'a>(
             &'a mut self,
             buf: &'a mut [u8],
-        ) -> [ReadExactFuture<'a, Self>]
+        ) -> ReadExactFuture<'a, Self>
         where
             Self: Unpin,
         {
@@ -373,7 +372,6 @@ extension_trait! {
             Chain { first: self, second: next, done_first: false }
         }
     }
-}
 
 impl<T: Read + ?Sized> ReadExt for T {}
 
diff --git a/src/io/seek/mod.rs b/src/io/seek/mod.rs
index af7cafcf..f2b60932 100644
--- a/src/io/seek/mod.rs
+++ b/src/io/seek/mod.rs
@@ -6,7 +6,6 @@ use crate::io::SeekFrom;
 
 pub use futures_io::AsyncSeek as Seek;
 
-extension_trait! {
     #[doc = r#"
         Extension methods for [`Seek`].
 
@@ -40,13 +39,12 @@ extension_trait! {
         fn seek(
             &mut self,
             pos: SeekFrom,
-        ) -> [SeekFuture<'_, Self>]
+        ) -> SeekFuture<'_, Self>
         where
             Self: Unpin,
         {
             SeekFuture { seeker: self, pos }
         }
     }
-}
 
 impl<T: Seek + ?Sized> SeekExt for T {}
diff --git a/src/io/write/mod.rs b/src/io/write/mod.rs
index b18d80f0..d73c40d8 100644
--- a/src/io/write/mod.rs
+++ b/src/io/write/mod.rs
@@ -14,7 +14,6 @@ use crate::io::{self, IoSlice};
 
 pub use futures_io::AsyncWrite as Write;
 
-extension_trait! {
     #[doc = r#"
         Extension methods for [`Write`].
 
@@ -49,7 +48,7 @@ extension_trait! {
         fn write<'a>(
             &'a mut self,
             buf: &'a [u8],
-        ) -> [WriteFuture<'a, Self>]
+        ) -> WriteFuture<'a, Self>
         where
             Self: Unpin,
         {
@@ -75,7 +74,7 @@ extension_trait! {
             # Ok(()) }) }
             ```
         "#]
-        fn flush(&mut self) -> [FlushFuture<'_, Self>]
+        fn flush(&mut self) -> FlushFuture<'_, Self>
         where
             Self: Unpin,
         {
@@ -97,7 +96,7 @@ extension_trait! {
         fn write_vectored<'a>(
             &'a mut self,
             bufs: &'a [IoSlice<'a>],
-        ) -> [WriteVectoredFuture<'a, Self>]
+        ) -> WriteVectoredFuture<'a, Self>
         where
             Self: Unpin,
         {
@@ -133,7 +132,7 @@ extension_trait! {
         fn write_all<'a>(
             &'a mut self,
             buf: &'a [u8],
-        ) -> [WriteAllFuture<'a, Self>]
+        ) -> WriteAllFuture<'a, Self>
         where
             Self: Unpin,
         {
@@ -170,7 +169,7 @@ extension_trait! {
         fn write_fmt<'a>(
             &'a mut self,
             fmt: std::fmt::Arguments<'_>,
-        ) -> [WriteFmtFuture<'a, Self>]
+        ) -> WriteFmtFuture<'a, Self>
         where
             Self: Unpin,
         {
@@ -184,6 +183,5 @@ extension_trait! {
             WriteFmtFuture { writer: self, res: Some(res), buffer: None, amt: 0 }
         }
     }
-}
 
 impl<T: Write + ?Sized> WriteExt for T {}
diff --git a/src/stream/stream/mod.rs b/src/stream/stream/mod.rs
index 0ead0800..25aadfac 100644
--- a/src/stream/stream/mod.rs
+++ b/src/stream/stream/mod.rs
@@ -145,7 +145,6 @@ cfg_unstable! {
 
 pub use futures_core::stream::Stream as Stream;
 
-extension_trait! {
     #[doc = r#"
         Extension methods for [`Stream`].
 
@@ -177,7 +176,7 @@ extension_trait! {
             # }) }
             ```
         "#]
-        fn next(&mut self) -> [NextFuture<'_, Self>]
+        fn next(&mut self) -> NextFuture<'_, Self>
         where
             Self: Unpin,
         {
@@ -629,7 +628,7 @@ extension_trait! {
         "#]
         fn last(
             self,
-        ) -> [LastFuture<Self, Self::Item>]
+        ) -> LastFuture<Self, Self::Item>
         where
             Self: Sized,
         {
@@ -839,7 +838,7 @@ extension_trait! {
         fn min_by_key<B, F>(
             self,
             key_by: F,
-        ) -> [MinByKeyFuture<Self, Self::Item, F>]
+        ) -> MinByKeyFuture<Self, Self::Item, F>
         where
             Self: Sized,
             B: Ord,
@@ -875,7 +874,7 @@ extension_trait! {
         fn max_by_key<B, F>(
             self,
             key_by: F,
-        ) -> [MaxByKeyFuture<Self, Self::Item, F>]
+        ) -> MaxByKeyFuture<Self, Self::Item, F>
         where
             Self: Sized,
             B: Ord,
@@ -914,7 +913,7 @@ extension_trait! {
         fn min_by<F>(
             self,
             compare: F,
-        ) -> [MinByFuture<Self, F, Self::Item>]
+        ) -> MinByFuture<Self, F, Self::Item>
         where
             Self: Sized,
             F: FnMut(&Self::Item, &Self::Item) -> Ordering,
@@ -947,7 +946,7 @@ extension_trait! {
         "#]
         fn max(
             self,
-        ) -> [MaxFuture<Self, Self::Item>]
+        ) -> MaxFuture<Self, Self::Item>
         where
             Self: Sized,
             Self::Item: Ord,
@@ -980,7 +979,7 @@ extension_trait! {
         "#]
         fn min(
             self,
-        ) -> [MinFuture<Self, Self::Item>]
+        ) -> MinFuture<Self, Self::Item>
         where
             Self: Sized,
             Self::Item: Ord,
@@ -1018,7 +1017,7 @@ extension_trait! {
         fn max_by<F>(
             self,
             compare: F,
-        ) -> [MaxByFuture<Self, F, Self::Item>]
+        ) -> MaxByFuture<Self, F, Self::Item>
         where
             Self: Sized,
             F: FnMut(&Self::Item, &Self::Item) -> Ordering,
@@ -1082,7 +1081,7 @@ extension_trait! {
         fn nth(
             &mut self,
             n: usize,
-        ) -> [NthFuture<'_, Self>]
+        ) -> NthFuture<'_, Self>
         where
             Self: Unpin + Sized,
         {
@@ -1138,7 +1137,7 @@ extension_trait! {
         fn all<F>(
             &mut self,
             f: F,
-        ) -> [AllFuture<'_, Self, F, Self::Item>]
+        ) -> AllFuture<'_, Self, F, Self::Item>
         where
             Self: Unpin + Sized,
             F: FnMut(Self::Item) -> bool,
@@ -1187,7 +1186,7 @@ extension_trait! {
         fn find<P>(
             &mut self,
             p: P,
-        ) -> [FindFuture<'_, Self, P>]
+        ) -> FindFuture<'_, Self, P>
         where
             Self: Unpin + Sized,
             P: FnMut(&Self::Item) -> bool,
@@ -1215,7 +1214,7 @@ extension_trait! {
         fn find_map<F, B>(
             &mut self,
             f: F,
-        ) -> [FindMapFuture<'_, Self, F>]
+        ) -> FindMapFuture<'_, Self, F>
         where
             Self: Unpin + Sized,
             F: FnMut(Self::Item) -> Option<B>,
@@ -1249,7 +1248,7 @@ extension_trait! {
             self,
             init: B,
             f: F,
-        ) -> [FoldFuture<Self, F, B>]
+        ) -> FoldFuture<Self, F, B>
         where
             Self: Sized,
             F: FnMut(B, Self::Item) -> B,
@@ -1286,7 +1285,7 @@ extension_trait! {
         fn partition<B, F>(
             self,
             f: F,
-        ) -> [PartitionFuture<Self, F, B>]
+        ) -> PartitionFuture<Self, F, B>
         where
             Self: Sized,
             F: FnMut(&Self::Item) -> bool,
@@ -1322,7 +1321,7 @@ extension_trait! {
         fn for_each<F>(
             self,
             f: F,
-        ) -> [ForEachFuture<Self, F>]
+        ) -> ForEachFuture<Self, F>
         where
             Self: Sized,
             F: FnMut(Self::Item),
@@ -1378,7 +1377,7 @@ extension_trait! {
         fn any<F>(
             &mut self,
             f: F,
-        ) -> [AnyFuture<'_, Self, F, Self::Item>]
+        ) -> AnyFuture<'_, Self, F, Self::Item>
         where
             Self: Unpin + Sized,
             F: FnMut(Self::Item) -> bool,
@@ -1614,7 +1613,7 @@ extension_trait! {
             &mut self,
             init: T,
             f: F,
-        ) -> [TryFoldFuture<'_, Self, F, T>]
+        ) -> TryFoldFuture<'_, Self, F, T>
         where
             Self: Unpin + Sized,
             F: FnMut(B, Self::Item) -> Result<T, E>,
@@ -1659,7 +1658,7 @@ extension_trait! {
         fn try_for_each<F, E>(
             &mut self,
             f: F,
-        ) -> [TryForEachFuture<'_, Self, F>]
+        ) -> TryForEachFuture<'_, Self, F>
         where
             Self: Unpin + Sized,
             F: FnMut(Self::Item) -> Result<(), E>,
@@ -1741,7 +1740,7 @@ extension_trait! {
         "#]
         #[cfg(feature = "unstable")]
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
-        fn unzip<A, B, FromA, FromB>(self) -> [UnzipFuture<Self, FromA, FromB>]
+        fn unzip<A, B, FromA, FromB>(self) -> UnzipFuture<Self, FromA, FromB>
         where
         FromA: Default + Extend<A>,
         FromB: Default + Extend<B>,
@@ -1805,7 +1804,7 @@ extension_trait! {
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
         fn collect<'a, B>(
             self,
-        ) -> [Pin<Box<dyn Future<Output = B> + 'a + Send>>]
+        ) -> Pin<Box<dyn Future<Output = B> + 'a + Send>>
         where
             Self: Sized + 'a + Send,
             B: FromStream<Self::Item>,
@@ -1879,7 +1878,7 @@ extension_trait! {
         fn partial_cmp<S>(
            self,
            other: S
-        ) -> [PartialCmpFuture<Self, S>]
+        ) -> PartialCmpFuture<Self, S>
         where
             Self: Sized + Stream,
             S: Stream,
@@ -1919,7 +1918,7 @@ extension_trait! {
         fn position<P>(
            &mut self,
            predicate: P,
-        ) -> [PositionFuture<'_, Self, P>]
+        ) -> PositionFuture<'_, Self, P>
         where
             Self: Unpin + Sized,
             P: FnMut(Self::Item) -> bool,
@@ -1957,7 +1956,7 @@ extension_trait! {
         fn cmp<S>(
            self,
            other: S
-        ) -> [CmpFuture<Self, S>]
+        ) -> CmpFuture<Self, S>
         where
             Self: Sized + Stream,
             S: Stream,
@@ -1988,7 +1987,7 @@ extension_trait! {
         "#]
         #[cfg(feature = "unstable")]
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
-        fn count(self) -> [CountFuture<Self>]
+        fn count(self) -> CountFuture<Self>
         where
             Self: Sized,
         {
@@ -2023,7 +2022,7 @@ extension_trait! {
         fn ne<S>(
            self,
            other: S
-        ) -> [NeFuture<Self, S>]
+        ) -> NeFuture<Self, S>
         where
             Self: Sized,
             S: Sized + Stream,
@@ -2060,7 +2059,7 @@ extension_trait! {
         fn ge<S>(
            self,
            other: S
-        ) -> [GeFuture<Self, S>]
+        ) -> GeFuture<Self, S>
         where
             Self: Sized + Stream,
             S: Stream,
@@ -2097,7 +2096,7 @@ extension_trait! {
         fn eq<S>(
            self,
            other: S
-        ) -> [EqFuture<Self, S>]
+        ) -> EqFuture<Self, S>
         where
             Self: Sized + Stream,
             S: Sized + Stream,
@@ -2134,7 +2133,7 @@ extension_trait! {
         fn gt<S>(
            self,
            other: S
-        ) -> [GtFuture<Self, S>]
+        ) -> GtFuture<Self, S>
         where
             Self: Sized + Stream,
             S: Stream,
@@ -2171,7 +2170,7 @@ extension_trait! {
         fn le<S>(
            self,
            other: S
-        ) -> [LeFuture<Self, S>]
+        ) -> LeFuture<Self, S>
         where
             Self: Sized + Stream,
             S: Stream,
@@ -2208,7 +2207,7 @@ extension_trait! {
         fn lt<S>(
            self,
            other: S
-        ) -> [LtFuture<Self, S>]
+        ) -> LtFuture<Self, S>
         where
             Self: Sized + Stream,
             S: Stream,
@@ -2252,7 +2251,7 @@ extension_trait! {
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
         fn sum<'a, S>(
             self,
-        ) -> [Pin<Box<dyn Future<Output = S> + 'a>>]
+        ) -> Pin<Box<dyn Future<Output = S> + 'a>>
         where
             Self: Sized + Stream<Item = S> + 'a,
             S: Sum<Self::Item>,
@@ -2298,7 +2297,7 @@ extension_trait! {
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
         fn product<'a, P>(
             self,
-        ) -> [Pin<Box<dyn Future<Output = P> + 'a>>]
+        ) -> Pin<Box<dyn Future<Output = P> + 'a>>
         where
             Self: Sized + Stream<Item = P> + 'a,
             P: Product,
@@ -2306,7 +2305,6 @@ extension_trait! {
             Product::product(self)
         }
     }
-}
 
 impl<T: Stream + ?Sized> StreamExt for T {}
 
diff --git a/src/utils.rs b/src/utils.rs
index 96f24fd2..d1b49727 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -233,41 +233,3 @@ macro_rules! cfg_default {
         )*
     }
 }
-
-/// Defines an extension trait for a base trait.
-///
-/// In generated docs, the base trait will contain methods from the extension trait. In actual
-/// code, the base trait will be re-exported and the extension trait will be hidden. We then
-/// re-export the extension trait from the prelude.
-///
-/// Inside invocations of this macro, we write a definitions that looks similar to the final
-/// rendered docs, and the macro then generates all the boilerplate for us.
-#[allow(unused_macros)]
-#[doc(hidden)]
-macro_rules! extension_trait {
-    (
-        #[doc = $doc_ext:tt]
-        pub trait $ext:ident: $name:ident {
-            $($body_ext:tt)*
-        }
-    ) => {
-        // The extension trait that adds methods to any type implementing the base trait.
-        #[doc = $doc_ext]
-        pub trait $ext: $name {
-            extension_trait!(@ext [$($body_ext)*] -> []);
-        }
-    };
-
-    // Parse the return type in an extension method.
-    (@ext [-> [$f:ty] $($tail:tt)*] -> [$($accum:tt)*]) => {
-        extension_trait!(@ext [$($tail)*] -> [$($accum)* -> $f]);
-    };
-
-    // Parse a token.
-    (@ext [$token:tt $($tail:tt)*] -> [$($accum:tt)*]) => {
-        extension_trait!(@ext [$($tail)*] -> [$($accum)* $token]);
-    };
-
-    // Handle the end of the token list.
-    (@ext [] -> [$($accum:tt)*]) => { $($accum)* };
-}