Analyzer and front end disagree on whether to report an error

[stereotype441]

I'm opening this bug as a placeholder while I investigate further. For now I'm assigning to area-language since I don't know whether the analyzer or front end is misbehaving. When I know more, I'll update the bug description and reassign to the appropriate area.

The analyzer and the front end disagree as to whether the following code (from #48952) is erroneous:

typedef SettingOrFunc = int? Function<T>(ContainsValue<T> tag);

class ContainsValue<T> {
  final T val;
  ContainsValue(this.val);
}

class UsesSetting {
  final SettingOrFunc? setting;
  UsesSetting({this.setting});

  /// Do stuff with wrappedValue here,
  /// for my project, if wrappedValue is/returns null,
  /// default values are used otherwise uses the wrappedValue's return.
}

void main(List<String> args) {
  UsesSetting(
    setting: <num>(t) => t.val == 50 ? 0 : null, // is fine
  );
  UsesSetting(
    setting: <num>(t) => t.val < 50 ? 0 : null, // throws analysis error:
                                                // The operator '<' isn't defined for the type 'Object'.
                                                // Try defining the operator '<'. dart(undefined_operator)
  );
}