class RuboCop::Cop::Style::DefWithParentheses

end
do_something
def Baz.foo
# good
end
do_something
def Baz.foo()
# bad
@example
def foo() do_something end
# good (without parentheses it’s a syntax error)
def foo = do_something
# good
def foo() = do_something
# bad
end
do_something
def foo
# good
end
do_something
def foo()
# bad
@example
class/singleton methods are checked.
that does not take any arguments. Both instance and
Checks for parentheses in the definition of a method,

def on_def(node) 

def on_def(node)
  return if node.single_line? && !node.endless?
  return unless !node.arguments? && (node_arguments = node.arguments.source_range)
  add_offense(node_arguments) do |corrector|
    corrector.remove(node_arguments)
  end
end