diff --git a/src/future/future/mod.rs b/src/future/future/mod.rs
index 35651450..19432555 100644
--- a/src/future/future/mod.rs
+++ b/src/future/future/mod.rs
@@ -21,11 +21,6 @@ cfg_unstable_default! {
 }
 
 extension_trait! {
-    use core::pin::Pin;
-    use core::ops::{Deref, DerefMut};
-
-    use crate::task::{Context, Poll};
-
     #[doc = r#"
         A future represents an asynchronous computation.
 
@@ -393,40 +388,4 @@ extension_trait! {
             TimeoutFuture::new(self, dur)
         }
     }
-
-    impl<F: Future + Unpin + ?Sized> Future for Box<F> {
-        type Output = F::Output;
-
-        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<F: Future + Unpin + ?Sized> Future for &mut F {
-        type Output = F::Output;
-
-        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<P> Future for Pin<P>
-    where
-        P: DerefMut + Unpin,
-        <P as Deref>::Target: Future,
-    {
-        type Output = <<P as Deref>::Target as Future>::Output;
-
-        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<F: Future> Future for std::panic::AssertUnwindSafe<F> {
-        type Output = F::Output;
-
-        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
 }
diff --git a/src/io/buf_read/mod.rs b/src/io/buf_read/mod.rs
index 3ee6e30b..90bf339d 100644
--- a/src/io/buf_read/mod.rs
+++ b/src/io/buf_read/mod.rs
@@ -16,8 +16,6 @@ use crate::io;
 use crate::task::{Context, Poll};
 
 extension_trait! {
-    use std::ops::{Deref, DerefMut};
-
     #[doc = r#"
         Allows reading from a buffered byte stream.
 
@@ -283,62 +281,6 @@ extension_trait! {
             }
         }
     }
-
-    impl<T: BufRead + Unpin + ?Sized> BufRead for Box<T> {
-        fn poll_fill_buf(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-        ) -> Poll<io::Result<&[u8]>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-
-        fn consume(self: Pin<&mut Self>, amt: usize) {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<T: BufRead + Unpin + ?Sized> BufRead for &mut T {
-        fn poll_fill_buf(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-        ) -> Poll<io::Result<&[u8]>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-
-        fn consume(self: Pin<&mut Self>, amt: usize) {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<P> BufRead for Pin<P>
-    where
-        P: DerefMut + Unpin,
-        <P as Deref>::Target: BufRead,
-    {
-        fn poll_fill_buf(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-        ) -> Poll<io::Result<&[u8]>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-
-        fn consume(self: Pin<&mut Self>, amt: usize) {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl BufRead for &[u8] {
-        fn poll_fill_buf(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-        ) -> Poll<io::Result<&[u8]>> {
-            unreachable!()
-        }
-
-        fn consume(self: Pin<&mut Self>, amt: usize) {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
 }
 
 pub fn read_until_internal<R: BufReadExt + ?Sized>(
diff --git a/src/io/read/mod.rs b/src/io/read/mod.rs
index c8f4e28b..8c6d3a3e 100644
--- a/src/io/read/mod.rs
+++ b/src/io/read/mod.rs
@@ -22,12 +22,6 @@ pub use chain::Chain;
 pub use take::Take;
 
 extension_trait! {
-    use std::pin::Pin;
-    use std::ops::{Deref, DerefMut};
-
-    use crate::io;
-    use crate::task::{Context, Poll};
-
     #[doc = r#"
         Allows reading from a byte stream.
 
@@ -422,50 +416,6 @@ extension_trait! {
         }
 
     }
-
-    impl<T: Read + Unpin + ?Sized> Read for Box<T> {
-        fn poll_read(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            buf: &mut [u8],
-        ) -> Poll<io::Result<usize>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<T: Read + Unpin + ?Sized> Read for &mut T {
-        fn poll_read(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            buf: &mut [u8],
-        ) -> Poll<io::Result<usize>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<P> Read for Pin<P>
-    where
-        P: DerefMut + Unpin,
-        <P as Deref>::Target: Read,
-    {
-        fn poll_read(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            buf: &mut [u8],
-        ) -> Poll<io::Result<usize>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl Read for &[u8] {
-        fn poll_read(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            buf: &mut [u8],
-        ) -> Poll<io::Result<usize>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
 }
 
 /// Initializes a buffer if necessary.
diff --git a/src/io/seek/mod.rs b/src/io/seek/mod.rs
index 3b5036c8..748a1ed9 100644
--- a/src/io/seek/mod.rs
+++ b/src/io/seek/mod.rs
@@ -5,12 +5,6 @@ use seek::SeekFuture;
 use crate::io::SeekFrom;
 
 extension_trait! {
-    use std::ops::{Deref, DerefMut};
-    use std::pin::Pin;
-
-    use crate::io;
-    use crate::task::{Context, Poll};
-
     #[doc = r#"
         Allows seeking through a byte stream.
 
@@ -83,38 +77,4 @@ extension_trait! {
             SeekFuture { seeker: self, pos }
         }
     }
-
-    impl<T: Seek + Unpin + ?Sized> Seek for Box<T> {
-        fn poll_seek(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            pos: SeekFrom,
-        ) -> Poll<io::Result<u64>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<T: Seek + Unpin + ?Sized> Seek for &mut T {
-        fn poll_seek(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            pos: SeekFrom,
-        ) -> Poll<io::Result<u64>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<P> Seek for Pin<P>
-    where
-        P: DerefMut + Unpin,
-        <P as Deref>::Target: Seek,
-    {
-        fn poll_seek(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            pos: SeekFrom,
-        ) -> Poll<io::Result<u64>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
 }
diff --git a/src/io/write/mod.rs b/src/io/write/mod.rs
index 3dee9feb..b0ed8eec 100644
--- a/src/io/write/mod.rs
+++ b/src/io/write/mod.rs
@@ -13,11 +13,6 @@ use write_vectored::WriteVectoredFuture;
 use crate::io::{self, IoSlice};
 
 extension_trait! {
-    use std::pin::Pin;
-    use std::ops::{Deref, DerefMut};
-
-    use crate::task::{Context, Poll};
-
     #[doc = r#"
         Allows writing to a byte stream.
 
@@ -245,80 +240,4 @@ extension_trait! {
             WriteFmtFuture { writer: self, res: Some(res), buffer: None, amt: 0 }
         }
     }
-
-    impl<T: Write + Unpin + ?Sized> Write for Box<T> {
-        fn poll_write(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            buf: &[u8],
-        ) -> Poll<io::Result<usize>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-
-        fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-
-        fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<T: Write + Unpin + ?Sized> Write for &mut T {
-        fn poll_write(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            buf: &[u8],
-        ) -> Poll<io::Result<usize>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-
-        fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-
-        fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<P> Write for Pin<P>
-    where
-        P: DerefMut + Unpin,
-        <P as Deref>::Target: Write,
-    {
-        fn poll_write(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            buf: &[u8],
-        ) -> Poll<io::Result<usize>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-
-        fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-
-        fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl Write for Vec<u8> {
-        fn poll_write(
-            self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            buf: &[u8],
-        ) -> Poll<io::Result<usize>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-
-        fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-
-        fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<()>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
 }
diff --git a/src/stream/stream/mod.rs b/src/stream/stream/mod.rs
index af7407a2..90c5cb7a 100644
--- a/src/stream/stream/mod.rs
+++ b/src/stream/stream/mod.rs
@@ -144,10 +144,6 @@ cfg_unstable! {
 }
 
 extension_trait! {
-    use std::ops::{Deref, DerefMut};
-
-    use crate::task::{Context, Poll};
-
     #[doc = r#"
         An asynchronous stream of values.
 
@@ -2389,40 +2385,4 @@ extension_trait! {
             Product::product(self)
         }
     }
-
-    impl<S: Stream + Unpin + ?Sized> Stream for Box<S> {
-        type Item = S::Item;
-
-        fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<S: Stream + Unpin + ?Sized> Stream for &mut S {
-        type Item = S::Item;
-
-        fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<P> Stream for Pin<P>
-    where
-        P: DerefMut + Unpin,
-        <P as Deref>::Target: Stream,
-    {
-        type Item = <<P as Deref>::Target as Stream>::Item;
-
-        fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
-
-    impl<S: Stream> Stream for std::panic::AssertUnwindSafe<S> {
-        type Item = S::Item;
-
-        fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-            unreachable!("this impl only appears in the rendered docs")
-        }
-    }
 }
diff --git a/src/utils.rs b/src/utils.rs
index 77111143..8b8ee23f 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -259,26 +259,8 @@ macro_rules! extension_trait {
         pub trait $ext:ident: $base:path {
             $($body_ext:tt)*
         }
-
-        // Shim trait impls that only appear in docs.
-        $($imp:item)*
     ) => {
-        // A fake `impl Future` type that doesn't borrow.
-        #[allow(dead_code)]
-        mod owned {
-            #[doc(hidden)]
-            pub struct ImplFuture<T>(core::marker::PhantomData<T>);
-        }
-
-        // Render a fake trait combining the bodies of the base trait and the extension trait.
-        #[cfg(feature = "docs")]
-        #[doc = $doc]
-        pub trait $name {
-            extension_trait!(@doc [$($body_base)* $($body_ext)*] -> []);
-        }
-
-        // When not rendering docs, re-export the base trait from the futures crate.
-        #[cfg(not(feature = "docs"))]
+        // Re-export the base trait from the futures crate.
         pub use $base as $name;
 
         // The extension trait that adds methods to any type implementing the base trait.
@@ -289,36 +271,18 @@ macro_rules! extension_trait {
 
         // Blanket implementation of the extension trait for any type implementing the base trait.
         impl<T: $name + ?Sized> $ext for T {}
-
-        // Shim trait impls that only appear in docs.
-        $(#[cfg(feature = "docs")] $imp)*
     };
 
     // Parse the return type in an extension method.
-    (@doc [-> impl Future<Output = $out:ty> [$f:ty] $($tail:tt)*] -> [$($accum:tt)*]) => {
-        extension_trait!(@doc [$($tail)*] -> [$($accum)* -> owned::ImplFuture<$out>]);
-    };
     (@ext [-> impl Future<Output = $out:ty> [$f:ty] $($tail:tt)*] -> [$($accum:tt)*]) => {
         extension_trait!(@ext [$($tail)*] -> [$($accum)* -> $f]);
     };
 
     // Parse a token.
-    (@doc [$token:tt $($tail:tt)*] -> [$($accum:tt)*]) => {
-        extension_trait!(@doc [$($tail)*] -> [$($accum)* $token]);
-    };
     (@ext [$token:tt $($tail:tt)*] -> [$($accum:tt)*]) => {
         extension_trait!(@ext [$($tail)*] -> [$($accum)* $token]);
     };
 
     // Handle the end of the token list.
-    (@doc [] -> [$($accum:tt)*]) => { $($accum)* };
     (@ext [] -> [$($accum:tt)*]) => { $($accum)* };
-
-    // Parse imports at the beginning of the macro.
-    ($import:item $($tail:tt)*) => {
-        #[cfg(feature = "docs")]
-        $import
-
-        extension_trait!($($tail)*);
-    };
 }