class T::Private::Methods::DeclBuilder

def generated
  check_live!
  if !decl.generated.equal?(ARG_NOT_PROVIDED)
    raise BuilderError.new("You can't call .generated multiple times in a signature.")
  end
  if !decl.checked.equal?(ARG_NOT_PROVIDED)
    raise BuilderError.new("You can't use .generated with .checked.")
  end
  if !decl.on_failure.equal?(ARG_NOT_PROVIDED)
    raise BuilderError.new("You can't use .generated with .on_failure.")
  end
  decl.generated = true
  self
end