declare.rs

com::declare! {
    // A COM interface declared here
    #[uuid(...)]
    pub interface IOldSchool {
        fn foo();
        fn bar();
    }

    // A COM class declared here (not defined here)
    #[uuid(...)]
    pub class ExternalClass : IOldSchool;

    // A COM class defined here
    #[uuid(...)]
    pub class ExportedClass : IOldSchool {
        my_field: usize,
    }

    // A local COM class defined here (no uuid needed)
    class LocalClass : IOldSchool {...}
}

impl ExportedClass {
    fn foo() { ... }
    fn bar() { ... }
}

impl Default for ExportedClass {
  fn default() -> Self { ... }
}

impl Default for LocalClass {
  fn default() -> Self { ... }
}