    import ceylon.language.meta.model { Value, Attribute, AppliedType = Type, IncompatibleTypeException }

    """A value declaration.

       <a name="toplevel-sample"></a>
       ### Usage sample for toplevel value

       Getting a model requires applying type arguments to the
       value declaration with [[apply]] in order to be able to read that value. For example, here is how you would
       obtain a value model that you can read from a toplevel attribute declaration:

           String foo = "Hello";

           void test(){
               // We need to apply the the foo declaration in order to get the foo value model
               Value<String> valueModel = `value foo`.apply<String>();
               // This will print: Hello
               print(valueModel.get());
           }

       <a name="member-sample"></a>
       ### Usage sample for attributes

       For attributes it is a bit longer, because attributes need to be applied the containing type, so you should
       use [[memberApply]] and start by giving the containing closed type:

           class Outer(){
               shared String foo => "Hello";
           }

           void test(){
               // Apply the containing closed type `Outer` to the attribute declaration `Outer.foo`
               Attribute<Outer,String> valueModel = `value Outer.foo`.memberApply<Outer,String>(`Outer`);
               // We now have an Attribute, which needs to be applied to a containing instance in order to become a
               // readable value:
               Value<String> boundValueModel = valueModel(Outer());
               // This will print: Hello
               print(boundValueModel.get());
           }
       """
    shared sealed interface ValueDeclaration
            satisfies FunctionOrValueDeclaration {

        "True if this declaration is annotated with [[variable|ceylon.language::variable]]."
        shared formal Boolean variable;

        "True if this declaration is an `object` declaration, whose type is an anonymous class."
        shared formal Boolean objectValue;

        "This value's anonymous class declaration if this value is an object declaration. `null` otherwise."
        shared formal ClassDeclaration? objectClass;

        "Applies this value declaration in order to obtain a value model.
         See [this code sample](#toplevel-sample) for an example on how to use this."
        throws(`class IncompatibleTypeException`, "If the specified `Get` or `Set` type arguments are not compatible with the actual result.")
        shared formal Value<Get, Set> apply<Get=Anything, Set=Nothing>();

        "Applies the given closed container type to this attribute declaration in order to obtain an attribute model.
         See [this code sample](#member-sample) for an example on how to use this."
        throws(`class IncompatibleTypeException`, "If the specified `Container`, `Get` or `Set` type arguments are not compatible with the actual result.")
        shared formal Attribute<Container, Get, Set> memberApply<Container=Nothing, Get=Anything, Set=Nothing>(AppliedType<Container> containerType);

        "Reads the current value of this toplevel value."
        shared default Anything get()
                => apply<Anything, Nothing>().get();

        "Reads the current value of this attribute on the given container instance."
        throws(`class IncompatibleTypeException`, "If the specified container is not compatible with this attribute.")
        shared default Anything memberGet(Object container)
                => memberApply<Nothing, Anything, Nothing>(`Nothing`).bind(container).get();

        "Sets the current value of this toplevel value."
        shared default void set(Anything newValue)
            => apply<Anything,Nothing>().setIfAssignable(newValue);

        "Sets the current value of this attribute on the given container instance."
        throws(`class IncompatibleTypeException`, "If the specified container or new value type is not compatible with this attribute.")
        shared formal void memberSet(Object container, Anything newValue);
        //=> memberApply<Nothing, Anything, Nothing>(`Nothing`).bind(container).setIfAssignable(newValue);

        "Returns the setter declaration for this variable.

         For modelling purposes `variable` reference
         values have a SetterDeclaration even though there is no
         such setter explicit in the source code."
        shared formal SetterDeclaration? setter;

    }