[PROPOSAL] Operator overload for function calls

[EliteMasterEric]

Haxe currently allows for abstracts to redefine unary operators such as a++, as well as binary operators, such as a + b, and even other operators such as ternary, range, or array access. However, based on the documentation I have read, it does not currently allow overriding the function call operation.

I would imagine this would look something like so:

abstract CallableThing(CallableThingBase) {
  @:op(Int, Bool)
  public function call(arg1:Int, arg2:Bool):Void {
    trace('Arg 1: $arg1');
    trace('Arg 2: $arg2');
  }
}

...

var c:CallableThing = new CallableThing();
// You can now make calls to C as though it were an Int->Bool->Void function.
c(1, true);

At compilation time, c(1, true) would be replaced with CallableThing_Impl_.call(c, 1, true).

The main sticking points here is the actual syntax; @:op(Int, Bool) is redundant since we already have the function signature, @:op(()) can't necessarily be interpreted by the compiler I don't think, and the @:callable metadata is already in use.

[Simn]

See #93 for an discussion on this topic.

[EliteMasterEric]

Hey @Simn,

After reading your linked discussion, I concluded that #93 is related (and possibly a prerequisite for this) but does not directly supersede this proposal.

This proposal is not referring to the overload keyword but to this specific feature:

https://haxe.org/manual/types-abstract-operator-overloading.html

I am essentially proposing that a new operator be added (which abstracts could replace) which would allow for abstract objects to be called as though they were anonymous functions.

[EliteMasterEric]

Was reading through proposals and re-discovered this old issue I raised.

For anyone searching here, this feature was actually implemented in Haxe 4.3.0, in the form of @:op(a()).

https://try.haxe.org/#25e52a54