class RBS::Definition

def initialize(type_name:, entry:, self_type:, ancestors:)
  case entry
  when Environment::ClassEntry, Environment::ModuleEntry
    # ok
  else
    unless entry.decl.is_a?(AST::Declarations::Interface)
      raise "Declaration should be a class, module, or interface: #{type_name}"
    end
  end
  unless self_type.is_a?(Types::ClassSingleton) || self_type.is_a?(Types::Interface) || self_type.is_a?(Types::ClassInstance)
    raise "self_type should be the type of declaration: #{self_type}"
  end
  @type_name = type_name
  @self_type = self_type
  @entry = entry
  @methods = {}
  @instance_variables = {}
  @class_variables = {}
  @ancestors = ancestors
end