Macro wrap_resolve_callback 

macro_rules! wrap_resolve_callback {
    ($ vis : vis struct $ name : ident ; impl ResolveCallback { $ ($ (# [$ attrs_name : meta]) * fn $ method_name : ident (& $ self : ident $ (, $ arg_name : ident : $ arg_type : ty) * $ (,) ?) $ (-> $ return_type : ty) ? { $ ($ body : tt) * }) * }) => { ... };
    ($ vis : vis struct $ name : ident $ (< $ ($ generic_type : ident : $ first_generic_type_bound : tt $ (+ $ generic_type_bound : tt) *) , + $ (,) ? >) ? { $ ($ field_vis : vis $ field_name : ident : $ field_type : ty) , * $ (,) ? } impl ResolveCallback { $ ($ (# [$ attrs_name : meta]) * fn $ method_name : ident (& $ self : ident $ (, $ arg_name : ident : $ arg_type : ty) * $ (,) ?) $ (-> $ return_type : ty) ? { $ ($ body : tt) * }) * }) => { ... };
}

Implement the WrapResolveCallback trait for the specified struct. You can declare more members for your struct, and in the impl ResolveCallback block you can override default methods implemented by the ImplResolveCallback trait.

Example

wrap_resolve_callback! {
    struct MyResolveCallback {
        payload: String,
    }

    impl ResolveCallback {
        // ...
    }
}

fn make_my_struct() -> ResolveCallback {
    MyResolveCallback::new("payload".to_string())
}