fix warning

Cargo.toml

@@ -26,7 +26,6 @@ default = [
   "async-task",
   "crossbeam-channel",
   "crossbeam-deque",
-  "futures-timer",
   "kv-log-macro",
   "log",
   "mio",
@@ -42,6 +41,7 @@ std = [
   "crossbeam-utils",
   "futures-core/std",
   "futures-io",
+  "futures-timer",
   "memchr",
   "once_cell",
   "pin-utils",

src/utils.rs

@@ -257,11 +257,6 @@ macro_rules! extension_trait {
         $(#[cfg(feature = "docs")] $imp)*
     };
 
-    // Optimization: expand `$head` eagerly before starting a new method definition.
-    (@ext ($($head:tt)*) #[doc = $d:literal] $($tail:tt)*) => {
-        $($head)* extension_trait!(@ext (#[doc = $d]) $($tail)*);
-    };
-
     // Parse the return type in an extension method.
     (@doc ($($head:tt)*) -> impl Future<Output = $out:ty> $(+ $lt:lifetime)? [$f:ty] $($tail:tt)*) => {
         extension_trait!(@doc ($($head)* -> owned::ImplFuture<$out>) $($tail)*);