RSCG – UnionGen

name UnionGen
nuget https://www.nuget.org/packages/UnionGen/
link https://github.com/markushaslinger/union_source_generator
author M. Haslinger

Generating unions between types

 

This is how you can use UnionGen .

The code that you start with is

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<Project Sdk="Microsoft.NET.Sdk">
 
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net8.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
 
    <PropertyGroup>
        <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
        <CompilerGeneratedFilesOutputPath>$(BaseIntermediateOutputPath)\GX</CompilerGeneratedFilesOutputPath>
    </PropertyGroup>
 
    <ItemGroup>
      <PackageReference Include="UnionGen" Version="1.4.0" />
    </ItemGroup>
 
</Project>

The code that you will use is

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using UnionTypesDemo;
 
Console.WriteLine("Save or not");
var data = SaveToDatabase.Save(0);
Console.WriteLine(data.IsNotFound);
data = SaveToDatabase.Save(1);
Console.WriteLine(data.IsResultOfInt32);
 
Console.WriteLine(data.AsResultOfInt32());
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using UnionGen.Types;
using UnionGen;
namespace UnionTypesDemo;
 
[Union<Result<int>, NotFound>]
public partial struct ResultSave
{
}
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using UnionGen.Types;
 
namespace UnionTypesDemo;
 
public class SaveToDatabase
{
    public static ResultSave Save(int i)
    {
        if(i ==0)
        {
            return new NotFound();
        }
        return new Result<int>(i);
    }
}

 

The code that is generated is

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// <auto-generated by UnionSourceGen />
#nullable enable
using System;
namespace UnionTypesDemo
{
 
    public readonly partial struct ResultSave : IEquatable<ResultSave>
    {
        private readonly UnionGen.Types.Result<int> _value0;
        private readonly UnionGen.Types.NotFound _value1;
        private readonly UnionGen.InternalUtil.StateByte _state;
 
        private ResultSave(int index, int actualTypeIndex)
        {
            _state = new UnionGen.InternalUtil.StateByte(index, actualTypeIndex);
        }
 
        public ResultSave(UnionGen.Types.Result<int> value): this(0, 0)
        {
            _value0 = value;
        }
 
        public ResultSave(UnionGen.Types.NotFound value): this(1, 1)
        {
            _value1 = value;
        }
 
        [Obsolete(UnionGen.InternalUtil.UnionGenInternalConst.DefaultConstructorWarning, true)]
        public ResultSave(): this(0, 0) {}
 
        public bool IsResultOfInt32 => _state.Index == 0;
        public bool IsNotFound => _state.Index == 1;
 
        public UnionGen.Types.Result<int> AsResultOfInt32() =>
            IsResultOfInt32
                ? _value0
                : throw UnionGen.InternalUtil.ExceptionHelper.ThrowNotOfType(GetTypeName(0), GetTypeName(_state.ActualTypeIndex));
         
        public UnionGen.Types.NotFound AsNotFound() =>
            IsNotFound
                ? _value1
                : throw UnionGen.InternalUtil.ExceptionHelper.ThrowNotOfType(GetTypeName(1), GetTypeName(_state.ActualTypeIndex));
 
        public static implicit operator ResultSave(UnionGen.Types.Result<int> value) => new ResultSave(value);
        public static implicit operator ResultSave(UnionGen.Types.NotFound value) => new ResultSave(value);
        public static bool operator ==(ResultSave left, ResultSave right) => left.Equals(right);
        public static bool operator !=(ResultSave left, ResultSave right) => !left.Equals(right);
 
        public TResult Match<TResult>(Func<UnionGen.Types.Result<int>, TResult> withResultOfInt32, Func<UnionGen.Types.NotFound, TResult> withNotFound) =>      
            _state.ActualTypeIndex switch
            {
                0 => withResultOfInt32(_value0),
                1 => withNotFound(_value1),
                _ => throw UnionGen.InternalUtil.ExceptionHelper.ThrowUnknownTypeIndex(_state.ActualTypeIndex)
            };
 
        public void Switch(Action<UnionGen.Types.Result<int>> forResultOfInt32, Action<UnionGen.Types.NotFound> forNotFound)     
        {
            switch (_state.ActualTypeIndex)
            {
                case 0: forResultOfInt32(_value0); break;
                case 1: forNotFound(_value1); break;
                default: throw UnionGen.InternalUtil.ExceptionHelper.ThrowUnknownTypeIndex(_state.ActualTypeIndex);
            }
        }
 
        public override string ToString() =>        
            _state.Index switch
            {
                0 => _value0.ToString()!,
                1 => _value1.ToString()!,
                _ => throw UnionGen.InternalUtil.ExceptionHelper.ThrowUnknownTypeIndex(_state.Index)
            };
 
        public bool Equals(ResultSave other) =>
            _state.Index == other._state.Index
                && _state.Index switch
                {
                    0 => _value0.Equals(other._value0),
                    1 => _value1.Equals(other._value1),
                    _ => false
                };
 
        public override bool Equals(object? obj)
        {
            if (ReferenceEquals(null, obj))
            {
                return false;
            }
            return obj is ResultSave other && Equals(other);
        }
 
        public override int GetHashCode(){     
            unchecked
            {
                var hash = _state.Index switch
                {
                    0 => _value0.GetHashCode(),
                    1 => _value1.GetHashCode(),
                    _ => 0
                };
                return (hash * 397) ^ _state.Index;
            }
        }
 
        public string GetTypeName(int index) =>
            index switch
            {
                0 => "UnionGen.Types.Result<int>",
                1 => "UnionGen.Types.NotFound",
                _ => throw UnionGen.InternalUtil.ExceptionHelper.ThrowUnknownTypeIndex(index)
            };
 
    }
 
}

Code and pdf at

https://ignatandrei.github.io/RSCG_Examples/v2/docs/UnionGen