Attribute Macro provides 

#[provides]

Annotates an impl block containing a function that provides an instance of a certain type

Static inject (default)

#[provides] or #[provides(static_inject)] on an impl of type T provides instances of type T, without any specialities.

 #[provides]
 impl ProvidedStatic {
     pub fn new(inner: usize) -> Self {
         Self {
            inner    
        }
     }
 }

Scoped inject

#[provides(scoped_inject)] on an impl of type T provides instances of type Rc<RefCell<T>>.

The provided instance will be a reference-counted pointer (Rc) that is shared in the outer scope, i.e., pointers provided by an individual scoped binding will point to the same instance.

 #[provides(scoped_inject)]
 impl ProvidedScoped {
     pub fn new(inner: usize) -> Self {
         Self {
            inner    
        }
     }
 }

Singleton inject

#[provides(singleton_inject)] on an impl of type T provides instances of type Arc<RwLock<T>>.

The provided instance will be an atomically reference-counted pointer (Arc) that is shared globally, i.e., pointers provided by any singleton binding will point to the same instance.

Functions providing a singleton instance cannot depend on any arguments.

 #[provides(singleton_inject)]
 impl ProvidedSingleton {
     pub fn new() -> Self {
         Self { }
     }
 }