Macro delegate_disposal 

macro_rules! delegate_disposal {
    (
        $(#[$meta:meta])*
        $name:ident<$($generic:tt),+ $(,)?>,
        $inner:ty $(,)?
        where $($where_clause:tt)+
    ) => { ... };
    (
        $(#[$meta:meta])*
        $name:ident<$($generic:tt),+ $(,)?>,
        $inner:ty
        $(,)?
    ) => { ... };
    (
        @impl
        [$($meta:tt)*]
        [$name:ident]
        [$($generic:tt),+]
        [$inner:ty]
        [$($struct_where:tt)*]
        [$($where_clause:tt)*]
    ) => { ... };
}

Defines a named disposal type that delegates Disposable::dispose to an inner disposal value.

This macro is specifically intended to put a short, stable name in front of a disposal type with two or more nested type-wrapper layers. Count layers along the deepest path through the type: Outer<D> has one layer, while Outer<Inner<D>> has two. Use this macro for the latter and for deeper compositions. Every instantiated concrete generic type counts as a layer; for example, OptionDisposal<ConcreteDisposal<'a, T>> has two layers.

Do not use this macro for a disposal type with only one wrapper layer. Write and return that concrete type directly instead.

The generated type implements Disposable by forwarding to the inner value. It also implements conversion from the inner value to the generated type. Use DisposableExt::into_subscription to convert the inner value directly into a Subscription of the generated type.