Avoid single void argument

[ykmnkmi]

A feature that allows you to pass a function with no arguments to a function that accepts function with one void argument:

void doSomething() {}

Stream<void> stream;
Future<void> future;
stream.listen(doSomething);
future.then(doSomething);
doSomething();

instead

void doSomething([void _]) {}

[lrhn]

For this to work, we'd likely have to wrap the function going in so that it has the correct type. That is, assigning a function f of type X Function() to a context expecting an X Function(void) (or X Function([void])) will automatically wrap it as (void _) => f();.
That's type coercion, something Dart has so far shied away from. It has a number of consequences, the main one is that it introduces a new function with a different identity. If you do Set<void Function(void)> s = {}; s.add(f); s.remove(f);, there is a real risk that the two functions won't be identical. They might be equal, but that's something we have to work for.

Would the feature only work for void parameters? Would it work for more than one void parameter? Would it work if there are more non-void parameters, and only trailing (or named) void parameters are missing?

I'm not sure that complexity outweighs just doing stream.listen((_) => something());.

[mateusfccp]

If you feel like, you can make an extension method, like:

import 'dart:async';

void main() {
  final s = StreamController<void>();
  s.stream.listen(doSomething.v);
}

void doSomething() {}

extension FunctionVoider<T> on T Function() {
  T Function(void) get v => (_) => this();
}

[ykmnkmi]

Due to strong typing, I have to write a type for _, without void type Missing parameter type for '_' error thrown:

request.response.close().then((void _) { /* */ });

Can we use void like in C without _:

request.response.close().then((void) { /* */ });