Fix placement of doc comment on c++ method shim
diff --git a/macro/src/expand.rs b/macro/src/expand.rs
index 91208e6..1bc2fd1 100644
--- a/macro/src/expand.rs
+++ b/macro/src/expand.rs
@@ -302,8 +302,8 @@
             }
         },
         Some(receiver_type) => quote! {
-            #doc
             impl #receiver_type {
+                #doc
                 pub fn #ident(#(#all_args,)*) #ret {
                     extern "C" {
                         #decl