Create Signal type for better autocomplete and compiler errors

[AaronRecord]

Describe the project you are working on

Godot

Describe the problem or limitation you are having in your project

Using strings for signals results in worse compiler errors/autocomplete/refactoring tools

Describe the feature / enhancement and how it helps to overcome the problem or limitation

I think there should be a Signal type for signals that (maybe) inherits Callable (kind of like C# events).
Object would no longer need connect(), disconnect(), emit_signal()

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Here's some of my ideas for how it could look:

GDScript:

# player.gd
signal on_death(score: int)

func die():
	on_death.call(score)
	# or if callables ever support this
	on_death(score)
	# or maybe if using callables wouldn't make sense, something like
	on_death.emit(score)


# death_screen.gd
player.on_death.connect(show)

func show(score: int):
	# do stuff

C++:

// base_button.h
public:
	Signal pressed; // something like this

// my_class.cpp
my_button->pressed.connect(callable_mp(this, &MyClass::do_stuff));
// or maybe like C#
my_button->pressed += callable_mp(this, &MyClass::do_stuff);

If this enhancement will not be used often, can it be worked around with a few lines of script?

No

Is there a reason why this should be core and not an add-on in the asset library?

Signals are core

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See also: #2557

[dalexeev]

This has already been done.

[KoBeWi]

Yep, closing.

[AaronRecord]

I guess I got confused because most places in the c++ codebase still use strings for the signal name, is this just a gdscript thing?

[Calinou]

I guess I got confused because most places in the c++ codebase still use strings for the signal name, is this just a gdscript thing?

Indeed, it's only used in GDScript for now. I'm not sure if there are plans to use the Signal type in C++. See also #2152.

[YuriSizov]

Yes, engine uses strings for that. To make the process a bit more controlled you can use the CoreStringNames singleton.

_curve->connect(CoreStringNames::get_singleton()->changed, callable_mp(this, &CurveTexture::_update));
emit_signal(CoreStringNames::get_singleton()->changed);

Edit: Though Calinou's proposal would be better.