fix(derive): Allow other attributes with subcommand that has subcommands

This was overlooked when we added support for `#[clap(subcommand)]` to
variants.

Fixes #3504

clap_derive/src/attrs.rs

@@ -127,15 +127,9 @@ impl Attrs {
                         "parse attribute is not allowed for subcommand"
                     );
                 }
-                if res.has_explicit_methods() {
-                    abort!(
-                        res.kind.span(),
-                        "methods in attributes are not allowed for subcommand"
-                    );
-                }
+
                 use syn::Fields::*;
                 use syn::FieldsUnnamed;
-
                 let field_ty = match variant.fields {
                     Named(_) => {
                         abort!(variant.span(), "structs are not allowed for subcommand");

tests/derive/subcommands.rs

@@ -296,7 +296,9 @@ fn external_subcommand_optional() {
 fn enum_in_enum_subsubcommand() {
     #[derive(Parser, Debug, PartialEq)]
     pub enum Opt {
-        #[clap(subcommand)]
+        #[clap(alias = "l")]
+        List,
+        #[clap(subcommand, alias = "d")]
         Daemon(DaemonCommand),
     }
 
@@ -309,11 +311,20 @@ fn enum_in_enum_subsubcommand() {
     let result = Opt::try_parse_from(&["test"]);
     assert!(result.is_err());
 
+    let result = Opt::try_parse_from(&["test", "list"]).unwrap();
+    assert_eq!(Opt::List, result);
+
+    let result = Opt::try_parse_from(&["test", "l"]).unwrap();
+    assert_eq!(Opt::List, result);
+
     let result = Opt::try_parse_from(&["test", "daemon"]);
     assert!(result.is_err());
 
     let result = Opt::try_parse_from(&["test", "daemon", "start"]).unwrap();
     assert_eq!(Opt::Daemon(DaemonCommand::Start), result);
+
+    let result = Opt::try_parse_from(&["test", "d", "start"]).unwrap();
+    assert_eq!(Opt::Daemon(DaemonCommand::Start), result);
 }
 
 #[test]