DirStructureAsync: carry the struct's where clause over into the generated future enums

dir-structure-macros/src/dir_structure_async/read_from_async.rs

@@ -240,7 +240,8 @@ pub(super) fn future_impl_enum(
     let first_ty = &first.actual_field_ty_perform;
     let ty_name = &st.ident;
 
-    let where_clause_read_future = merge_where_clause(None, read_async.clauses.clone());
+    let where_clause_read_future =
+        merge_where_clause(st.generics.where_clause.clone(), read_async.clauses.clone());
 
     let vis = &st.vis;
 

dir-structure-macros/src/dir_structure_async/write_to_async_ref.rs

@@ -264,7 +264,10 @@ pub(super) fn future_impl_enum(
         quote! {}
     };
 
-    let where_clause_write_future = merge_where_clause(None, write_async_ref.clauses.clone());
+    let where_clause_write_future = merge_where_clause(
+        st.generics.where_clause.clone(),
+        write_async_ref.clauses.clone(),
+    );
 
     let vis = &st.vis;
 

dir-structure-tools/tests/async_tests.rs

@@ -467,3 +467,40 @@ async fn versioned_doesnt_call_write_if_not_changed() {
     assert_eq!(std::fs::read_to_string(d.join("f1.txt")).unwrap(), "f2");
     assert_eq!(dir.f1.count.load(Ordering::SeqCst), 1);
 }
+
+mod derive_where_clause {
+    //! Regression test: the future enums generated by `DirStructureAsync` must
+    //! inherit the derived struct's `where` clause.
+    //!
+    //! Compiling this module is the test: without the struct's bounds being
+    //! carried over into the generated code, the derive expansion fails with
+    //! `<Vfs as VfsCore>::Path: MyTrait is not satisfied`.
+
+    use dir_structure::DirStructureAsync;
+    use dir_structure::traits::vfs::{PathType, VfsCore};
+    use dir_structure_tools::dir_children::{DirChildren, Filter};
+
+    trait MyTrait {}
+    impl MyTrait for std::path::Path {}
+
+    struct MyFilter;
+    impl<P> Filter<P> for MyFilter
+    where
+        P: PathType + MyTrait + ?Sized,
+    {
+        fn allows(_path: &P) -> bool {
+            true
+        }
+    }
+
+    #[allow(dead_code)]
+    #[derive(DirStructureAsync)]
+    struct MyFilterDir<Vfs>
+    where
+        Vfs: VfsCore,
+        Vfs::Path: MyTrait,
+    {
+        #[dir_structure(path = self)]
+        children: DirChildren<String, MyFilter, Vfs::Path>,
+    }
+}