Dart Analyzer can't seem to figure out whether a List child is const or new

[maryx]

• Dart SDK Version: dart --version didn't work but flutter --version gives Tools • Dart 2.0.0-dev.48.0.flutter-fe606f890b

• Linux

  It seems like the Dart Analyzer can't determine whether the child of a <Widget>[] is new or const, so we have to manually specify new. E.g. for this code:

  final rating = getRatingFromAPI();
  final numReviews = getReviewsFromAPI();
  ...
  Widget _buildRating() {
  return Row(
    mainAxisSize: MainAxisSize.min,
    children: <Widget>[
      Text( // this one doesn't need a `new` for some reason
        rating.toStringAsFixed(1),
        style: _secondaryTextStyle,
      ),
      Container( // this one doesn't need a `new` either
        margin: EdgeInsets.symmetric(horizontal: 8.0),
        child: Text('hello'),
      ),
      new Text( // this one needs a new. If omitted, see error below
        '(${numReviews})',
        style: _secondaryTextStyle,
      ),
    ],
  );
  }

  If I omit the new for the third child, I get error • Prefer const literals as parameters of constructors on @immutable classes at package:... • prefer_const_literals_to_create_immutables and a green squiggle under the word <Widget> in VS Code.

Is this expected?

[matanlurey]

@maryx:

It seems like the Dart Analyzer can't determine whether the child of a <Widget>[] is new or const, so we have to manually specify new. E.g. for this code:

This feature was reverted. There is no such thing as "automatic const" anymore, only "optional new". Once you specify the context as const once, then the remaining constructor calls are implicitly const. Consider:

class Animal {
  const Animal();
}

void main() {
  // Same as "final animals = [new Animal()]"
  final animals = [Animal()];

  // Same as "const animals = const [const Animal()]"
  const animals = [Animal()]
}

In your case children: is not a const context.

---

re: prefer_const_literals_to_create_immutables

You might want to also file this as dart-lang/linter, as it isn't part of the SDK proper: https://github.com/dart-lang/linter/issues

[maryx]

Ah thanks, I hadn't been sure where to file this - redirecting and closing this.