7.8.2 Interface Members
The members of an interface consist of the members introduced by its member declarations and the members inherited from its base interfaces.
Only nested types, methods, properties, and events may be members of an interface. Methods and properties may not have a body. Interface members are implicitly Public and may not specify an access modifier. Interface members have no scope, and they must always be qualified.
InterfaceMemberDeclaration ::= NonModuleDeclaration | EventMemberDeclaration | MethodMemberDeclaration | PropertyMemberDeclaration