Flutter 'bug'

main.dart

import 'package:flutter/material.dart';

void main() {
  return runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: SegmentsView(),
    );
  }
}

typedef InSegment = bool Function(String m);
class SegmentArguments {
  final String title;
  final InSegment inSegment;

  SegmentArguments(this.title, this.inSegment);
}

class SegmentViewState extends State<SegmentView> {
  List<String> mc = ["Hi!"];

  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    final SegmentArguments args = ModalRoute.of(context).settings.arguments;
    return Scaffold(
      appBar: AppBar(
        title: Text(args.title),
      ),
      body: Center(
        child: finiteList(mc.where((String s) => args.inSegment(s)).toList(), (String s) => ListTile(title: Text(s))),
      ),
    );
  }
}

class SegmentView extends StatefulWidget {
  SegmentView({Key key}) : super(key: key);
  @override
  SegmentViewState createState() => SegmentViewState();
}

ListView finiteList<A>(List<A> data, ListTile Function(A) tile) {
  return ListView.builder(
    padding: const EdgeInsets.all(16.0),
    itemCount: data.length * 2 - 1, // BUG BUG BUG
    itemBuilder: (context, i) {
      if(i.isOdd) return Divider();
      final index = i ~/ 2;
      return tile(data[index]);
    }
  );
}

class SegmentsView extends StatelessWidget {
  final List<SegmentArguments> segments = [
    SegmentArguments("Has elements", (m) => true),
    SegmentArguments("No elements", (m) => false),
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Bug example"),
      ),
      body: Center(
        child: finiteList<SegmentArguments>(segments, (SegmentArguments args) {
          return ListTile(
            title: Text(args.title),
            trailing: Icon(Icons.keyboard_arrow_right),
            onTap: () {
              Navigator.push(
                context,
                MaterialPageRoute(
                  builder: (context) => SegmentView(),
                  settings: RouteSettings(
                    arguments: args,
                  ),
                ),
              );
            }
          );
        })
      ),
    );
  }
}