Linter: Lint for `dynamic?`

[davidmorgan]

I'm surprised to find that dynamic? is allowed and we even see a few uses in google3 ...

Could we lint that you can always switch it to just dynamic? :)

[pq]

Or perhaps this should be an analyzer diagnostic? (Would anyone ever want to opt-out?)

/fyi @srawlins @bwilkerson

[srawlins]

@leafpetersen @munificent is dynamic? different from dynamic in any way? It'd be awkward to immediately default report against using something specified in the spec...

[srawlins]

Currently the analyzer even allows dynamic dispatch on dynamic?:

void f(dynamic? a) {
  print(a + 2);
}

[bwilkerson]

There's no difference between dynamic and dynamic?, so there's no value in allowing it in code. I doubt that there would be any objections to making it a hint, especially given that hints can be ignored if necessary.

[leafpetersen]

Yeah, dynamic? and void? are completely useless. Never? could be hinted to be equivalent to Null. Null? is also useless. FutureOr<T>? is useless if T is nullable, but you could argue that it's useful documentation.

[srawlins]

Thanks for the responses! I agree that it should be Hinted then; dynamic?, void?, etc. would look to me like I'm supposed to read some sort of signal from that ? and I would carefully tiptoe around it for a few minutes before realizing it is meaningless.

[move[bot]]

This issue was moved by pq to dart-lang/sdk#45165.