    "A function or value declaration."
    shared sealed interface FunctionOrValueDeclaration
        of FunctionDeclaration
         | ValueDeclaration
        satisfies NestableDeclaration {

        "True if this function or value is a parameter to a [[FunctionalDeclaration]]."
        shared formal Boolean parameter;

        "True if this function or value is a parameter and has a default value."
        shared formal Boolean defaulted;

        "True if this function or value is a parameter and is variadic (accepts a list of values)."
        shared formal Boolean variadic;
    }