Ink widget decoration visible or/and renders outside the ListView boundary up to the cacheExtent.

main.dart

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      height: 300,
      width: 100,
      child: ListView(
        // switching cache extent to 0 stop this.
        // cacheExtent: 0,
        children: List<int>.generate(50, (x) => x)
            .map((y) => Ink(
                  decoration: BoxDecoration(
                    color: Colors.pink,
                    border: Border(
                      bottom: BorderSide(color: Colors.green),
                    ),
                  ),
                  child: InkWell(
                    splashColor: Colors.green,
                    child: Icon(
                      Icons.plus_one,
                      size: 22,
                    ),
                    onTap: () {},
                  ),
                ))
            .toList(),
      ),
    );
  }
}