`=>` closures formatting in named argument list

[goderbauer]

The new dart formatter wants to format this as follows:

void _showDialog(Widget child, BuildContext context) {
  showCupertinoModalPopup<void>(
    context: context,
    builder:
        (BuildContext context) => Container(
          height: 216,
          padding: const EdgeInsets.only(top: 6.0),
          // The Bottom margin is provided to align the popup above the system
          // navigation bar.
          margin: EdgeInsets.only(
            bottom: MediaQuery.of(context).viewInsets.bottom,
          ),
          // Provide a background color for the popup.
          color: CupertinoColors.systemBackground.resolveFrom(context),
          // Use a SafeArea widget to avoid system overlaps.
          child: SafeArea(top: false, child: child),
        ),
  );
}

This gives the closure a lot of prominence over the other parameters and also causes more indentation reducing the effective line length for code inside the closure.

void _showDialog(Widget child, BuildContext context) {
  showCupertinoModalPopup<void>(
    context: context,
    builder: (BuildContext context) => Container(
      height: 216,
      padding: const EdgeInsets.only(top: 6.0),
      // The Bottom margin is provided to align the popup above the system
      // navigation bar.
      margin: EdgeInsets.only(
        bottom: MediaQuery.of(context).viewInsets.bottom,
      ),
      // Provide a background color for the popup.
      color: CupertinoColors.systemBackground.resolveFrom(context),
      // Use a SafeArea widget to avoid system overlaps.
      child: SafeArea(top: false, child: child),
    ),
  );
}

This formatting would visually also be more in line with the formatting I'd expect if builder were a list argument:

void _showDialog(Widget child, BuildContext context) {
  showCupertinoModalPopup<void>(
    context: context, 
    builder: <Widget>[
      longNameForAWidgetToMakeSureThisDoesNotFit,
      longNameForAWidgetToMakeSureThisDoesNotFit2,
      longNameForAWidgetToMakeSureThisDoesNotFit3,
    ],
  );
}

@munificent did mention that there are cases were this kind of formatting for => closures looks worse. I'm interested in seeing examples for that.

[FMorschel]

The same happens in https://github.com/dart-lang/dart_style/issues/1525 although it is not a named argument case but a cascade case.