Support for @checked on fields

[scheglov]

import 'package:meta/meta.dart';

class A {
  get foo => '';
  set foo(_) {}
}

class B extends A {
  @checked
  int foo;
}

Currently this code reports an error ERROR: Invalid override. The type of B.foo= ((int) → void) is not a subtype of A.foo= ((dynamic) → void). ([analyzer] bin/test.dart:10).

But if I encapsulate the field, then it works fine.

import 'package:meta/meta.dart';

class A {
  get foo => '';
  set foo(_) {}
}

class B extends A {
  int _foo;

  int get foo => _foo;

  void set foo(@checked int foo) {
    _foo = foo;
  }
}

Can / should we make it work similarly for the field case?

[scheglov]

@keertip

[jmesserly]

Great question! -- @leafpetersen thoughts?

[leafpetersen]

This sounds good to me.

[leafpetersen]

@sethladd

[sethladd]

Related to #25578

[jmesserly]

https://codereview.chromium.org/2346143003/

[leafpetersen]

If this doesn't already, we may want to consider making this imply @virtual. There's kind of no point otherwise, and I'm not sure there's any benefit in requiring both annotations.

[jmesserly]

@leafpetersen - here's a possible counter example?

abstract class BaseView {
  List<View> get children { ... }
  set children(List<View> views) { ... }
}
// intended to be sealed
class MyAppView extends BaseView {
  @checked List<MyChildView> children = [];
}

edit: add setter & extends :)

[jmesserly]

I'd hit send too fast, updated above example.

[leafpetersen]

Ah good point.