"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;
}
​