Allow not typing brackets in functions declaration if there are no args

[me2beats]

Ruby:

def f
  puts 'hi'
end

f()

In GDScript it could be like

func f:
    print('hi')

Or even without : (See #4699)

func f
    print('hi')

[dalexeev]

We prefer not to have multiple syntax options doing the same thing. For example, we have two dictionary styles, but the Lua style allows you to omit quotes for keys. We have two setter/getter styles, but the alternative style allows you to use a separate function like setget in 3.x. An alternative function declaration syntax would not bring any bonuses other than aesthetic ones. I think it's not worth it, it would only complicate parser, clutter documentation, etc.

Also, judging by the reactions and activity over almost 2 years, this proposal did not receive support.

However, we have 2 precedents for optional empty parentheses:

• signal my_signal vs signal my_signal();
• get: vs get(): (see Allow declaring a getter using get(): additionally to get: #8057).

Of course, we can say that they exist for historical reasons and this is not a sufficient reason to introduce another exception. It is also unclear what benefits the optional empty parentheses provide. #8057 requested support for parentheses, not their optionality.

Let's keep this discussion open for a while and see if the community shows interest in it, maybe new arguments will appear.