Fix the problem that Description derived macro do not support generic objects.

derive/src/description.rs

@@ -7,9 +7,10 @@ pub fn generate(desc_args: &args::Description) -> GeneratorResult<TokenStream> {
     let crate_name = get_crate_name(desc_args.internal);
     let ident = &desc_args.ident;
     let generics = &desc_args.generics;
+    let where_clause = &generics.where_clause;
     let doc = get_rustdoc(&desc_args.attrs)?.unwrap_or_default();
     let expanded = quote! {
-        impl #crate_name::Description for #ident #generics {
+        impl #generics #crate_name::Description for #ident #generics #where_clause {
             fn description() -> &'static str {
                 #doc
             }

tests/use_type_description.rs

@@ -32,6 +32,40 @@ pub async fn test_object() {
     );
 }
 
+#[async_std::test]
+pub async fn test_object_with_lifetime() {
+    /// Haha
+    #[derive(Description, Default)]
+    struct MyObj<'a>(&'a str);
+
+    #[Object(use_type_description)]
+    impl<'a> MyObj<'a> {
+        async fn value(&self) -> &str {
+            self.0
+        }
+    }
+
+    struct Query;
+
+    #[Object]
+    impl Query {
+        async fn obj(&self) -> MyObj<'_> {
+            todo!()
+        }
+    }
+
+    let schema = Schema::new(Query, EmptyMutation, EmptySubscription);
+    assert_eq!(
+        schema
+            .execute(r#"{ __type(name: "MyObj") { description } }"#)
+            .await
+            .data,
+        value!({
+            "__type": { "description": "Haha" }
+        })
+    );
+}
+
 #[async_std::test]
 pub async fn test_scalar() {
     /// Haha