A tiny fix for define_client_side.

The return type can only appear once.

Author: nnethercote

library/proc_macro/src/bridge/client.rs

@@ -223,10 +223,10 @@ pub(crate) use super::symbol::Symbol;
 
 macro_rules! define_client_side {
     ($($name:ident {
-        $(fn $method:ident($($arg:ident: $arg_ty:ty),* $(,)?) $(-> $ret_ty:ty)*;)*
+        $(fn $method:ident($($arg:ident: $arg_ty:ty),* $(,)?) $(-> $ret_ty:ty)?;)*
     }),* $(,)?) => {
         $(impl $name {
-            $(pub(crate) fn $method($($arg: $arg_ty),*) $(-> $ret_ty)* {
+            $(pub(crate) fn $method($($arg: $arg_ty),*) $(-> $ret_ty)? {
                 Bridge::with(|bridge| {
                     let mut buf = bridge.cached_buffer.take();