Flutter / Dart Error: The argument type 'Null Function(Key)' can't be assigned to the parameter type 'void Function(Object)'

Question

Android Studio: Launching lib/main.dart on iPhone 11 Pro Max in debug mode...

Compiler message:
/Users/[User]/.pub-cache/hosted/pub.dartlang.org/reorderables-0.2.12/lib/src/widgets/reorderable_flex.dart:727:18: Error: The argument type 'Null Function(Key)' can't be assigned to the parameter type 'void Function(Object)'.
 - 'Key' is from 'package:flutter/src/foundation/key.dart' ('/Users/[User]/Development/flutter/packages/flutter/lib/src/foundation/key.dart').
 - 'Object' is from 'dart:core'.
        onLeave: (Key leaving) {},
                 ^
/Users/[User]/.pub-cache/hosted/pub.dartlang.org/reorderables-0.2.12/lib/src/widgets/reorderable_wrap.dart:951:18: Error: The argument type 'Null Function(int)' can't be assigned to the parameter type 'void Function(Object)'.
 - 'Object' is from 'dart:core'.
        onLeave: (int leaving) {},
                 ^
/Users/[User]/.pub-cache/hosted/pub.dartlang.org/reorderables-0.2.12/lib/src/widgets/reorderable_wrap.dart:957:18: Error: The argument type 'Null Function(int)' can't be assigned to the parameter type 'void Function(Object)'.
 - 'Object' is from 'dart:core'.
        onLeave: (int leaving) {},
                 ^
/Users/[User]/.pub-cache/hosted/pub.dartlang.org/reorderables-0.2.12/lib/src/widgets/reorderable_sliver.dart:842:18: Error: The argument type 'Null Function(int)' can't be assigned to the parameter type 'void Function(Object)'.
 - 'Object' is from 'dart:core'.
        onLeave: (int leaving) {},
                 ^
Target kernel_snapshot failed: Exception: Errors during snapshot creation: null
Failed to build bundle.
Error launching application on iPhone 11 Pro Max.

Can't get an answer to pass trough this issue, any help will be greatly appreciated ☃

Solution

Answered by Simon Binder via dart-lang/TALK-general:

This is an error in the reorderables package, which you probably depend on. A report and workaround is here: hanshengchiu/reorderables#52

Change in pubspec.yaml:

#  reorderables: ^0.2.12
  reorderables:
    git:
      url: git://github.com/hanshengchiu/reorderables.git