(...)->void must be a subtype of (...)->dynamic.

[floitschG]

Strong mode needs to allow functions that return void when a function that returns dynamic is expected.

Example use case:

T run<T>(T f()) {
  print("running");
  var t = f();
  print("done running");
  return t;
}

void printRunning() { print("running"); }
run<dynamic>(printRunning);

Ideally, we would like to write void in the generic type (or infer it): #27504

While this issue should stand on its own, it decreases the priority of #27504.

[leafpetersen]

@bwilkerson @jmesserly There's an analyzer and a DDC component to this, could you each take the respective parts?

[jmesserly]

Yeah I can take a shot at this. Shouldn't be too hard.

edit: and presumably we also want to allow "void" in inference.

[dgrove]

I'll split this up into analyzer and DDC pieces.

[jmesserly]

thanks. I don't mind doing both BTW, it's probably pretty simple.

[leafpetersen]

Status: out for implementation.

[jmesserly]

Huh. I might be missing something but this seems to be implemented already in Analyzer strong mode.

[jmesserly]

DDC also appears to work already. I added an Analyzer and DDC test using the code example provided. Tentatively closing, let me know if there was something else we'd like to fix here.