main.dart

void main(){
    final bar2= Bar2();
    assert(bar2.bar1 =='test1');
    assert(bar2.bar1 =='test2');

    final bar = Bar('test1');
    assert(bar.bar1 == 'test1');
    assert(bar.bar2 == 'test2');
}


abstract class Foo {
    String get bar2 => 'test1';

    final String foo2;

    Foo(this.foo2);
}


class Bar extends Foo {
    final String bar1;
    Bar(this.bar1) : super('test2');
}

class Foo1 {
    String get bar1 => 'test1';
}

mixin Foo2 {
    String get bar2 => 'test2';
}

class Bar2 with Foo1, Foo2 {
}

m