    import ceylon.language.meta.model {
        Applicable,
        FunctionModel,
        Type,
        Qualified,
        IncompatibleTypeException,
        TypeApplicationException
    }

    """A function declaration.

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

       Because some functions have type parameters, getting a model requires applying type arguments to the
       function declaration with [[apply]] in order to be able to invoke that function. For example, here is how you would
       obtain a function model that you can invoke from a toplevel function declaration:

           String foo<T>(){
               return "Hello, our T is: ``typeLiteral<T>()``";
           }

           void test(){
               // We need to apply the Integer closed type to the foo declaration in order to get the foo<Integer> function model
               Function<String,[]> functionModel = `function foo`.apply<String,[]>(`Integer`);
               // This will print: Hello, our T is: ceylon.language::Integer
               print(functionModel());
           }

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

       For methods it is a bit longer, because methods need to be applied not only their type arguments but also
       the containing type, so you should use [[memberApply]] and start by giving the containing closed type:

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

           void test(){
               // apply the containing closed type `Outer` to the method declaration `Outer.hello`
               Method<Outer,String,[]> methodModel = `function Outer.hello`.memberApply<Outer,String,[]>(`Outer`);
               // We now have a Method, which needs to be applied to a containing instance in order to become an
               // invokable function:
               Function<String,[]> boundMethodModel = methodModel(Outer());
               // This will print: Hello
               print(boundMethodModel());
           }
       """
    shared sealed interface FunctionalDeclaration
            satisfies GenericDeclaration {

        "True if the current declaration is an annotation class or function."
        shared formal Boolean annotation;

        "The list of parameter declarations for this functional declaration."
        shared formal FunctionOrValueDeclaration[] parameterDeclarations;

        "Gets a parameter declaration by name. Returns `null` if no such parameter exists."
        shared formal FunctionOrValueDeclaration? getParameterDeclaration(String name);

        "Applies the given closed type arguments to this function declaration in order to obtain a function model.
         See [this code sample](#toplevel-sample) for an example on how to use this."
        throws(`class IncompatibleTypeException`, "If the specified `Return` or `Arguments` type arguments are not compatible with the actual result.")
        throws(`class TypeApplicationException`, "If the specified closed type argument values are not compatible with the actual result's type parameters.")
        since("1.2.0")
        shared formal FunctionModel<Return, Arguments>& Applicable<Return, Arguments> apply<Return=Anything, Arguments=Nothing>(Type<>* typeArguments)
                given Arguments satisfies Anything[];

        "Applies the given closed container type and type arguments to this method declaration in order to obtain a method model.
         See [this code sample](#member-sample) for an example on how to use this."
        throws(`class IncompatibleTypeException`, "If the specified `Container`, `Return` or `Arguments` type arguments are not compatible with the actual result.")
        throws(`class TypeApplicationException`, "If the specified closed container type or type argument values are not compatible with the actual result's container type or type parameters.")
        since("1.2.0")
        shared formal FunctionModel<Return, Arguments>&Qualified<FunctionModel<Return, Arguments>, Container> memberApply<Container=Nothing, Return=Anything, Arguments=Nothing>(Type<Object> containerType, Type<>* typeArguments)
                given Arguments satisfies Anything[];
        //shared formal FunctionModel<Return, Arguments>& Applicable<Return, Arguments>&Qualified<FunctionModel<Return, Arguments>&Applicable<Return, Arguments>, Container> memberApply<Container=Nothing, Return=Anything, Arguments=Nothing>(Type<Object> containerType, Type<>* typeArguments)
                //given Arguments satisfies Anything[];

        "Invokes the underlying toplevel function, by applying the specified type arguments and value arguments."
        throws(`class IncompatibleTypeException`, "If the specified type or value arguments are not compatible with this toplevel function.")
        since("1.2.0")
        shared default Anything invoke(Type<>[] typeArguments = [], Anything* arguments)
                => apply<Anything, Nothing>(*typeArguments).apply(*arguments);

        "Invokes the underlying method, by applying the specified type arguments and value arguments."
        throws(`class IncompatibleTypeException`, "If the specified container, type or value arguments are not compatible with this method.")
        since("1.2.0")
        shared formal Anything memberInvoke(Object container, Type<>[] typeArguments = [], Anything* arguments)/*
                => memberApply<Nothing, Anything, Nothing>(`Nothing`, *typeArguments).bind(container).apply(*arguments)*/;
    }