Also produce the wrapped token stream after the `compile_error!`

Otherwise we get a ton of unrelated error messages because we effectively
removed the tokens in the first place.

src/lib.rs

@@ -56,6 +56,7 @@ fn parse_function(item: syn::Item) -> Result<syn::ItemFn, TokenStream> {
         i => Err(quote_spanned! {
             i.span() =>
             compile_error!("`#[timed]` can only be used on functions");
+            #i
         }
         .into()),
     }