new lint: "no fancy createState"

[pq]

Follow-up from dart-archive/linter#1867 (and related to: #58075).

Bad:

MyState global;

class MyStateful extends StatefulWidget {
  @override
  MyState createState() {
    global = MyState();
    return global;
  } 
}

Good:

class MyStateful extends StatefulWidget {
  @override
  MyState createState() {
    return MyState();
  }
}

[pq]

Naming is hard. @rrousselGit, @bwilkerson: any ideas?

no_state_create_logic ?

[bwilkerson]

no_logic_in_create_state?

[pq]

@rrousselGit:

how literally should we interpret this advice?

Ultimately, createState has just a single possible implementation, that is:

@override
MyState createState() {
  return MyState();
}

With maybe replacing {} + return with () =>.
But other than that, it shouldn't change, ever.

Literally should we only except a block w/ one statement (a return statement instantiating a new State instance)?

[rrousselGit]

Yes, with no constructor parameter, no if, ternary, cascade...

[bwilkerson]

That does appear to trump the previous lint.