Equal LogicValue's may have unequal hash codes

[bbracker-int]

Describe the bug

Two LogicValue's which are equal according to == may have different hash codes.
This creates unintended behavior when LogicValue's are used in data structures which leverage hash codes, such as a Map.

Based on preliminary testing, my very rough guess is that LogicValue flavors which are based on the underlying _LogicValueEnum type have different hash codes than LogicValue flavors which are based on the int and BigInt types.

To Reproduce

I made a test which can be pasted into test/logic_value_test.dart
Try uncommenting the tests that fail to reproduce.

    test('hash', () {
      const lvEnum = LogicValue.one;
      final lvBool = LogicValue.ofBool(true);
      final lvInt = LogicValue.ofInt(1, 1);
      final lvBigInt = LogicValue.ofBigInt(BigInt.one, 1);
      final lvFilled = LogicValue.filled(1, lvEnum);

      // test hash codes directly
      // pass
      expect(lvEnum.hashCode == lvBool.hashCode, equals(true));
      expect(lvEnum.hashCode == lvFilled.hashCode, equals(true));
      expect(lvInt.hashCode == lvBigInt.hashCode, equals(true));
      // fail
      /*
      expect(lvEnum.hashCode == lvInt.hashCode, equals(true));
      expect(lvInt.hashCode == lvFilled.hashCode, equals(true));
      */

      // test hash codes through map usage
      Map<LogicValue, int> myLvMap;
      // pass
      myLvMap = {lvEnum: 7}..remove(lvBool);
      expect(myLvMap.length, equals(0));
      myLvMap = {lvEnum: 7}..remove(lvFilled);
      expect(myLvMap.length, equals(0));
      myLvMap = {lvInt: 7}..remove(lvBigInt);
      expect(myLvMap.length, equals(0));
      // fail
      /*
      myLvMap = {lvEnum: 7}..remove(lvInt);
      expect(myLvMap.length, equals(0));
      myLvMap = {lvInt: 7}..remove(lvFilled);
      expect(myLvMap.length, equals(0));
      */
    });

Expected behavior

Equality of value as judged by == implies equality of hash code.

Actual behavior

Equality of value as judged by == does not imply equality of hash code.

Additional: Dart SDK info

Dart SDK version: 2.18.4 (stable) (Unknown timestamp) on "linux_x64"

Additional: pubspec.yaml

name: rohd
description: The Rapid Open Hardware Development (ROHD) framework, a framework for describing and verifying hardware
version: 0.4.0
homepage: https://github.com/intel/rohd
repository: https://github.com/intel/rohd
issue_tracker: https://github.com/intel/rohd/issues
documentation: https://intel.github.io/rohd/rohd/rohd-library.html

environment:
  sdk: '>=2.18.0 <3.0.0'

dependencies:
  collection: ^1.15.0
  logging: ^1.0.1
  meta: ^1.3.0
  test: ^1.17.3

dev_dependencies:
  benchmark_harness: ^2.2.0

Additional: Context

I reproduced this bug in the most up-to-date version of the ROHD repo, on branch main, where the working directory is completely clean of local changes except for the aforementioned logic_value_test.dart file. That is where the pubspec.yaml comes from.

[mkorbel1]

A simple solution could be to use the _bigIntValue and _bigIntInvalid from #215 and compute the hash in LogicValue