From 0c22a9df6ce36fadc1fc4df312d75e9df41ada4b Mon Sep 17 00:00:00 2001
From: Pavan Kumar Sunkara <pavan.sss1991@gmail.com>
Date: Mon, 2 Mar 2020 11:46:40 +0100
Subject: [PATCH] Added support for unit-struct

---
 clap_derive/src/derives/clap.rs | 11 +++++++++++
 clap_derive/tests/basic.rs      |  8 ++++++++
 2 files changed, 19 insertions(+)

diff --git a/clap_derive/src/derives/clap.rs b/clap_derive/src/derives/clap.rs
index 08fb5144..cca20aec 100644
--- a/clap_derive/src/derives/clap.rs
+++ b/clap_derive/src/derives/clap.rs
@@ -31,6 +31,17 @@ pub fn derive_clap(input: &syn::DeriveInput) -> proc_macro2::TokenStream {
             dummies::clap_struct(ident);
             gen_for_struct(ident, &fields.named, &input.attrs)
         }
+        Struct(syn::DataStruct {
+            fields: syn::Fields::Unit,
+            ..
+        }) => {
+            dummies::clap_struct(ident);
+            gen_for_struct(
+                ident,
+                &punctuated::Punctuated::<syn::Field, token::Comma>::new(),
+                &input.attrs,
+            )
+        }
         Enum(ref e) => {
             dummies::clap_enum(ident);
             gen_for_enum(ident, &input.attrs, e)
diff --git a/clap_derive/tests/basic.rs b/clap_derive/tests/basic.rs
index a3d31fbd..6091ef9a 100644
--- a/clap_derive/tests/basic.rs
+++ b/clap_derive/tests/basic.rs
@@ -28,3 +28,11 @@ fn basic() {
         Opt::parse_from(&["test", "-a24", "--arg", "42"])
     );
 }
+
+#[test]
+fn unit_struct() {
+    #[derive(Clap, PartialEq, Debug)]
+    struct Opt;
+
+    assert_eq!(Opt {}, Opt::parse_from(&["test"]));
+}