Allow @doNotStore on callback parameters

[nex3]

It would be useful to be able to apply the @doNotStore annotation to parameters passed to callbacks in method signatures. This would allow implementations of methods that call these callbacks to provide parameters that are only valid during the lifetime of the callback, such as views on collections that are later changed after the callback returns.

[scheglov]

@pq @bwilkerson

[pq]

Sounds reasonable to me. Thanks @nex3!

@jefflim-google: curious if this use case has come up at all for you?

[jefflim-google]

TBH, it sounds like something that could be useful, but hasn't come up as a case we've thought about so far.

[matanlurey]

I could give you an example @jefflim-google:

class Button {
  final void Function(@doNotStore UIContext) onPress;

  Button({this.onPress});
}

I'd love for this to trigger a lint:

UIContext store;

Button({
  onPress: (context) {
    // LINT: do_not_store
    store = context;
  }
});