Extract subcommands into separate trait

.gitignore

@@ -28,3 +28,5 @@ clap-rs.iml
 
 # Auxiliary files
 test-results.test
+expanded.rs
+clap_derive/expanded.rs

clap_derive/examples/doc_comments.rs

@@ -1,6 +1,6 @@
 //! How to use doc comments in place of `help/long_help`.
 
-use clap::Clap;
+use clap::{Clap, Subcommand};
 
 /// A basic example for the usage of doc comments as replacement
 /// of the arguments `help`, `long_help`, `about` and `long_about`.
@@ -52,7 +52,7 @@ code) in the description:
     sub_command: SubCommand,
 }
 
-#[derive(Clap, Debug)]
+#[derive(Clap, Subcommand, Debug)]
 #[clap()]
 enum SubCommand {
     /// The same rules described previously for flags. Are

clap_derive/src/derives/attrs.rs

@@ -104,10 +104,7 @@ pub struct Attrs {
 /// The output of a generation method is not only the stream of new tokens but also the attribute
 /// information of the current element. These attribute information may contain valuable information
 /// for any kind of child arguments.
-pub struct GenOutput {
-    pub tokens: proc_macro2::TokenStream,
-    pub attrs: Attrs,
-}
+pub type GenOutput = (proc_macro2::TokenStream, Attrs);
 
 impl Method {
     pub fn new(name: Ident, args: TokenStream) -> Self {