added NotEqualTo

.gitea/workflows/publish-nuget.yaml

@@ -22,13 +22,17 @@ jobs:
       run: dotnet restore Railway/Railway.csproj
 
     - name: Setup nuget source
-      run: dotnet nuget add source --name gitea_registry https://gitea.jstdev.ru/api/packages/just/nuget/index.json
+      run: dotnet nuget add source --name gitea_registry ${{ vars.OUTPUT_NUGET_REGISTRY }} 
 
     - name: Create the package
       env:
         RELEASE_VERSION: ${{ gitea.ref_name }}
-      run: dotnet pack --no-restore --configuration Release --output nupkgs Railway/Railway.csproj `echo $RELEASE_VERSION | sed -E 's|^(v([0-9]+(\.[0-9]+){2}))(-([a-z0-9]+)){1}|/p:ReleaseVersion=\2 /p:VersionSuffix=\5|; s|^(v([0-9]+(\.[0-9]+){2}))$|/p:ReleaseVersion=\2|'`
+      run: >
+        dotnet pack --no-restore --configuration Release --output nupkgs Railway/Railway.csproj
+        `echo $RELEASE_VERSION | sed -E 's|^(v([0-9]+(\.[0-9]+){2}))(-([a-z0-9]+)){1}|/p:ReleaseVersion=\2 /p:VersionSuffix=\5|; s|^(v([0-9]+(\.[0-9]+){2}))$|/p:ReleaseVersion=\2|'`
 
     - name: Publish the package to Gitea
-      run: dotnet nuget push --source gitea_registry --api-key ${{ secrets.NUGET_PACKAGE_TOKEN }} nupkgs/*.nupkg
+      run: dotnet nuget push --source gitea_registry --api-key ${{ secrets.LOCAL_NUGET_PACKAGE_TOKEN }} nupkgs/*.nupkg
 
+    - name: Publish the package to NuGet.org
+      run: dotnet nuget push --source https://api.nuget.org/v3/index.json --api-key ${{ secrets.NUGET_PACKAGE_TOKEN }} nupkgs/*.nupkg

.vscode/settings.json

@@ -1,3 +1,4 @@
 {
-    "dotnet.defaultSolution": "Just.Railway.sln"
+    "dotnet.defaultSolution": "Just.Railway.sln",
+    "dotnetAcquisitionExtension.enableTelemetry": false
 }

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2023 JustFixMe
+Copyright (c) 2023-2024 JustFixMe
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -4,6 +4,117 @@ This library uses features of C# to achieve railway-oriented programming.
 
 The desire is to make somewhat user-friendly experience while using result-object pattern.
 
-## Contents
+## Features
 
-_Coming soon..._
+- Immutable ```Error``` class
+- ```Result``` object
+- A bunch of extensions to use result-object pattern with
+- ```Try``` extensions to wrap function calls with result-object
+- ```Ensure``` extensions to utilize result-object in validation scenarios
+
+## Getting Started
+
+### Install from NuGet.org
+
+```sh
+# install the package using NuGet
+dotnet add package Just.Railway
+```
+
+## Examples
+
+### Error
+
+```csharp
+using Just.Railway;
+Error expectedError = Error.New(type: "Some Error", message: "Some error detail");
+Error exceptionalError = Error.New(new Exception("Some Exception"));
+Error manyErrors = Error.Many(expectedError, exceptionalError);
+// the same result while using .Append(..) or +
+manyErrors = expectedError.Append(exceptionalError);
+manyErrors = expectedError + exceptionalError;
+```
+
+> **Note**
+> You can easily serialize/deserialize Error to and from JSON
+
+### Result
+
+#### As return value:
+
+```csharp
+Result Foo()
+{
+    // ...
+    if (SomeCondition())
+        return Result.Failure(Error.New("Some Error"));
+        // or just: return Error.New("Some Error");
+    // ...
+    return Result.Success();
+}
+
+Result<T> Bar()
+{
+    T value;
+    // ...
+    if (SomeCondition())
+        return Error.New("Some Error");
+    // ...
+    return value;
+}
+```
+
+#### Consume Result object
+
+```csharp
+Result<int> result = GetResult();
+
+string value = result
+    .Append("new") // -> Result<(int, string)>
+    .Map((i, s) => $"{s} result {i}") // -> Result<string>
+    .Match(
+        onSuccess: x => x,
+        onFailure: err => err.ToString()
+    );
+// value: "new result 1"
+
+Result<int> GetResult() => Result.Success(1);
+```
+
+#### Recover from failure
+
+```csharp
+Result<string> failed = new NotImplementedException();
+
+Result<string> result = failed.TryRecover(err => err.Type == "System.NotImplementedException"
+    ? "recovered"
+    : err);
+// result with value: "recovered"
+```
+
+### Try
+
+```csharp
+Result result = Try.Run(SomeAction);
+// you can pass up to 5 arguments like this
+result = Try.Run(SomeActionWithArguments, 1, 2.0, "3");
+
+// you also can call functions
+Result<int> resultWithValue = Try.Run(SomeFunction);
+
+void SomeAction() {}
+void SomeActionWithArguments(int a1, double a2, string? a3) {}
+int SomeFunction() => 1;
+```
+
+### Ensure
+
+```csharp
+int? value = GetValue();
+Result<int> result = Ensure.That(value) // -> Ensure<int?>
+    .NotNull() // -> Ensure<int>
+    .Satisfies(i => i < 100)
+    .Result();
+
+int? GetValue() => 1;
+```

Railway.SourceGenerator/Constants.cs

@@ -2,6 +2,5 @@ namespace Just.Railway.SourceGen;
 
 internal static class Constants
 {
-    public const int MaxResultTupleSize = 4;
+    public const int MaxResultTupleSize = 5;
-    
 }

Railway.SourceGenerator/EnsureExtensionsExecutor.cs

@@ -0,0 +1,504 @@
+using System.Collections.Generic;
+using System.Text;
+using Microsoft.CodeAnalysis;
+
+namespace Just.Railway.SourceGen;
+
+public sealed class EnsureExtensionsExecutor : IGeneratorExecutor
+{
+    public void Execute(SourceProductionContext context, Compilation source)
+    {
+        var methods = GenerateMethods();
+        var code = $$"""
+        #nullable enable
+        using System;
+        using System.Linq;
+        using System.Collections.Generic;
+        using System.Diagnostics.Contracts;
+        using System.CodeDom.Compiler;
+
+        namespace Just.Railway;
+
+        public static partial class Ensure
+        {
+        {{methods}}
+        }
+        """;
+
+        context.AddSource("Ensure.Extensions.g.cs", code);
+    }
+
+    private string GenerateMethods()
+    {
+        List<(string ErrorParameterDecl, string ErrorValueExpr)> errorGenerationDefinitions =
+        [
+            ("Error error = default!", "error"),
+            ("ErrorFactory errorFactory", "errorFactory(ensure.ValueExpression)")
+        ];
+
+        var sb = new StringBuilder();
+
+        sb.AppendLine("#region Satisfies");
+        errorGenerationDefinitions.ForEach(def => GenerateSatisfiesExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region Null");
+        errorGenerationDefinitions.ForEach(def => GenerateNullExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region NotNull");
+        errorGenerationDefinitions.ForEach(def => GenerateNotNullExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region NotEmpty");
+        errorGenerationDefinitions.ForEach(def => GenerateNotEmptyExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region NotWhitespace");
+        errorGenerationDefinitions.ForEach(def => GenerateNotWhitespaceExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region True");
+        errorGenerationDefinitions.ForEach(def => GenerateTrueExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region False");
+        errorGenerationDefinitions.ForEach(def => GenerateFalseExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region EqualTo");
+        errorGenerationDefinitions.ForEach(def => GenerateEqualToExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region NotEqualTo");
+        errorGenerationDefinitions.ForEach(def => GenerateNotEqualToExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region LessThan");
+        errorGenerationDefinitions.ForEach(def => GenerateLessThanExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region GreaterThan");
+        errorGenerationDefinitions.ForEach(def => GenerateGreaterThanExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region LessThanOrEqualTo");
+        errorGenerationDefinitions.ForEach(def => GenerateLessThanOrEqualToExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        sb.AppendLine("#region GreaterThanOrEqualTo");
+        errorGenerationDefinitions.ForEach(def => GenerateGreaterThanOrEqualToExtensions(sb, def.ErrorParameterDecl, def.ErrorValueExpr));
+        sb.AppendLine("#endregion");
+
+        return sb.ToString();
+    }
+
+    private void GenerateNotWhitespaceExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is empty or consists exclusively of white-space characters.\")";
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<string> NotWhitespace(this in Ensure<string> ensure, {{errorParameterDecl}})
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => string.IsNullOrWhiteSpace(ensure.Value)
+                    ? new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression)
+                    : new(ensure.Value!, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+
+    private void GenerateNotEmptyExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is empty.\")";
+        List<(string TemplateDef, string CollectionType, string NotEmptyTest)> typeOverloads =
+        [
+            ("<T>", "IEnumerable<T>", "ensure.Value?.Any() == true"),
+            ("<T>", "ICollection<T>", "ensure.Value?.Count > 0"),
+            ("<T>", "IReadOnlyCollection<T>", "ensure.Value?.Count > 0"),
+            ("<T>", "IList<T>", "ensure.Value?.Count > 0"),
+            ("<T>", "IReadOnlyList<T>", "ensure.Value?.Count > 0"),
+            ("<T>", "ISet<T>", "ensure.Value?.Count > 0"),
+            ("<T>", "IReadOnlySet<T>", "ensure.Value?.Count > 0"),
+            ("<TKey,TValue>", "IDictionary<TKey,TValue>", "ensure.Value?.Count > 0"),
+            ("<TKey,TValue>", "IReadOnlyDictionary<TKey,TValue>", "ensure.Value?.Count > 0"),
+            ("<T>", "T[]", "ensure.Value?.Length > 0"),
+            ("<T>", "List<T>", "ensure.Value?.Count > 0"),
+            ("<T>", "Queue<T>", "ensure.Value?.Count > 0"),
+            ("<T>", "HashSet<T>", "ensure.Value?.Count > 0"),
+            ("", "string", "!string.IsNullOrEmpty(ensure.Value)"),
+        ];
+
+        typeOverloads.ForEach(def => sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<{{def.CollectionType}}> NotEmpty{{def.TemplateDef}}(this in Ensure<{{def.CollectionType}}> ensure, {{errorParameterDecl}})
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => {{def.NotEmptyTest}}
+                    ? new(ensure.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """));
+    }
+
+    private void GenerateNullExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is not null.\")";
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<T?> Null<T>(this in Ensure<T?> ensure, {{errorParameterDecl}})
+            where T : struct
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => !ensure.Value.HasValue
+                    ? new(default(T?)!, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<T?> Null<T>(this in Ensure<T?> ensure, {{errorParameterDecl}})
+            where T : class
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value is null
+                    ? new(default(T?)!, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+
+    private void GenerateNotNullExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is null.\")";
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<T> NotNull<T>(this in Ensure<T?> ensure, {{errorParameterDecl}})
+            where T : struct
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value.HasValue
+                    ? new(ensure.Value.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<T> NotNull<T>(this in Ensure<T?> ensure, {{errorParameterDecl}})
+            where T : notnull
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value is not null
+                    ? new(ensure.Value!, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+
+    private void GenerateSatisfiesExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} does not satisfy the requirement.\")";
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<T> Satisfies<T>(this in Ensure<T> ensure, Func<T, bool> requirement, {{errorParameterDecl}})
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => requirement(ensure.Value)
+                    ? new(ensure.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+
+        GenerateSatisfiesAsyncExtensions(sb, "Task", errorParameterDecl, errorValueExpr, defaultErrorExpr);
+        GenerateSatisfiesAsyncExtensions(sb, "ValueTask", errorParameterDecl, errorValueExpr, defaultErrorExpr);
+    }
+
+    private void GenerateSatisfiesAsyncExtensions(StringBuilder sb, string taskType, string errorParameterDecl, string errorValueExpr, string defaultErrorExpr)
+    {
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<Ensure<T>> Satisfies<T>(this {{taskType}}<Ensure<T>> ensureTask, Func<T, bool> requirement, {{errorParameterDecl}})
+        {
+            var ensure = await ensureTask.ConfigureAwait(false);
+            return ensure.State switch
+            {
+                ResultState.Success => requirement(ensure.Value)
+                    ? new(ensure.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensureTask))
+            };
+        }
+        """);
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<Ensure<T>> Satisfies<T>(this Ensure<T> ensure, Func<T, {{taskType}}<bool>> requirement, {{errorParameterDecl}})
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => await requirement(ensure.Value).ConfigureAwait(false)
+                    ? new(ensure.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<Ensure<T>> Satisfies<T>(this {{taskType}}<Ensure<T>> ensureTask, Func<T, {{taskType}}<bool>> requirement, {{errorParameterDecl}})
+        {
+            var ensure = await ensureTask.ConfigureAwait(false);
+            return ensure.State switch
+            {
+                ResultState.Success => await requirement(ensure.Value).ConfigureAwait(false)
+                    ? new(ensure.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensureTask))
+            };
+        }
+        """);
+    }
+
+    private void GenerateTrueExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is not true.\")";
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<bool> True(this in Ensure<bool> ensure, {{errorParameterDecl}})
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value == true
+                    ? new(ensure.Value!, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<bool> True(this in Ensure<bool?> ensure, {{errorParameterDecl}})
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value == true
+                    ? new(ensure.Value.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+
+    private void GenerateFalseExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is not false.\")";
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<bool> False(this in Ensure<bool> ensure, {{errorParameterDecl}})
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value == false
+                    ? new(ensure.Value!, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<bool> False(this in Ensure<bool?> ensure, {{errorParameterDecl}})
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value == false
+                    ? new(ensure.Value.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+
+    private void GenerateEqualToExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is not equal to requirement.\")";
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<T> EqualTo<T>(this in Ensure<T> ensure, T requirement, {{errorParameterDecl}})
+            where T : IEquatable<T>
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value.Equals(requirement)
+                    ? new(ensure.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+
+    private void GenerateNotEqualToExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is equal to requirement.\")";
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<T> NotEqualTo<T>(this in Ensure<T> ensure, T requirement, {{errorParameterDecl}})
+            where T : IEquatable<T>
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => !ensure.Value.Equals(requirement)
+                    ? new(ensure.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+
+    private void GenerateLessThanExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is not less than requirement.\")";
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<T> LessThan<T>(this in Ensure<T> ensure, T requirement, {{errorParameterDecl}})
+            where T : IComparable<T>
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value.CompareTo(requirement) < 0
+                    ? new(ensure.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+
+    private void GenerateGreaterThanExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is not greater than requirement.\")";
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<T> GreaterThan<T>(this in Ensure<T> ensure, T requirement, {{errorParameterDecl}})
+            where T : IComparable<T>
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value.CompareTo(requirement) > 0
+                    ? new(ensure.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+
+    private void GenerateLessThanOrEqualToExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is greater than requirement.\")";
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<T> LessThanOrEqualTo<T>(this in Ensure<T> ensure, T requirement, {{errorParameterDecl}})
+            where T : IComparable<T>
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value.CompareTo(requirement) <= 0
+                    ? new(ensure.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+
+    private void GenerateGreaterThanOrEqualToExtensions(StringBuilder sb, string errorParameterDecl, string errorValueExpr)
+    {
+        string defaultErrorExpr = "?? Error.New(DefaultErrorType, $\"Value {{{ensure.ValueExpression}}} is less than requirement.\")";
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(EnsureExtensionsExecutor)}}", "1.0.0.0")]
+        public static Ensure<T> GreaterThanOrEqualTo<T>(this in Ensure<T> ensure, T requirement, {{errorParameterDecl}})
+            where T : IComparable<T>
+        {
+            return ensure.State switch
+            {
+                ResultState.Success => ensure.Value.CompareTo(requirement) >= 0
+                    ? new(ensure.Value, ensure.ValueExpression)
+                    : new({{errorValueExpr}} {{defaultErrorExpr}}, ensure.ValueExpression),
+                ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
+                _ => throw new EnsureNotInitializedException(nameof(ensure))
+            };
+        }
+        """);
+    }
+}

Railway.SourceGenerator/ExtensionsMethodGenerator.cs

@@ -1,14 +1,10 @@
-using System;
 using System.Collections.Generic;
-using System.Collections.Immutable;
-using System.Linq;
-using System.Text;
 using Microsoft.CodeAnalysis;
 
 namespace Just.Railway.SourceGen;
 
 [Generator]
-public class ResultMethodGenerator : IIncrementalGenerator
+public class ExtensionsMethodGenerator : IIncrementalGenerator
 {
     private readonly IEnumerable<IGeneratorExecutor> _executors = new IGeneratorExecutor[]
     {
@@ -17,6 +13,10 @@ public class ResultMethodGenerator : IIncrementalGenerator
         new ResultMapExecutor(),
         new ResultBindExecutor(),
         new ResultTapExecutor(),
+        new ResultTryRecoverExecutor(),
+        new ResultAppendExecutor(),
+        new TryExtensionsExecutor(),
+        new EnsureExtensionsExecutor(),
     };
 
     public void Initialize(IncrementalGeneratorInitializationContext context)

Railway.SourceGenerator/IGeneratorExecutor.cs

@@ -1,4 +1,3 @@
-using System;
 using Microsoft.CodeAnalysis;
 
 namespace Just.Railway.SourceGen;

Railway.SourceGenerator/ResultAppendExecutor.cs

@@ -0,0 +1,471 @@
+using System.Collections.Immutable;
+using System.Linq;
+using System.Text;
+using Microsoft.CodeAnalysis;
+
+namespace Just.Railway.SourceGen;
+
+internal sealed class ResultAppendExecutor : ResultExtensionsExecutor
+{
+    protected override string ExtensionType => "Append";
+
+    protected override void GenerateHelperMethods(StringBuilder sb)
+    {
+        sb.AppendLine("""
+        private static IEnumerable<string> GetBottom(ResultState r1, ResultState r2, string firstArg = "result", string secondArg = "next")
+        {
+            if (r1 == ResultState.Bottom)
+                yield return firstArg;
+            if (r2 == ResultState.Bottom)
+                yield return secondArg;
+        }
+        """);
+    }
+
+    protected override void GenerateMethodsForArgCount(StringBuilder sb, int argCount)
+    {
+        var templateArgNames = Enumerable.Range(1, argCount)
+            .Select(i => $"T{i}")
+            .ToImmutableArray();
+
+        string resultTypeDef = GenerateResultTypeDef(templateArgNames);
+        string resultValueExpansion = GenerateResultValueExpansion(templateArgNames);
+        string methodTemplateDecl = GenerateTemplateDecl(templateArgNames);
+
+        sb.AppendLine($"#region {resultTypeDef}");
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static {{resultTypeDef}} Append{{methodTemplateDecl}}(this in {{resultTypeDef}} result, Result next)
+        {
+            Error? error = null;
+            if ((result.State & next.State) == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
+            }
+
+            if (result.IsFailure)
+            {
+                error += result.Error;
+            }
+            if (next.IsFailure)
+            {
+                error += next.Error;
+            }
+
+            return error is null
+                ? Result.Success({{resultValueExpansion}})
+                : error;
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static {{resultTypeDef}} Append{{methodTemplateDecl}}(this in {{resultTypeDef}} result, Func<Result> nextFunc)
+        {
+            if (result.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(result));
+            }
+            else if (result.IsFailure)
+            {
+                return result.Error!;
+            }
+
+            var next = nextFunc();
+            if (next.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(nextFunc));
+            }
+            else if (next.IsFailure)
+            {
+                return next.Error!;
+            }
+
+            return Result.Success({{resultValueExpansion}});
+        }
+        """);
+
+        GenerateAsyncMethods("Task", sb, templateArgNames, resultTypeDef, resultValueExpansion);
+        GenerateAsyncMethods("ValueTask", sb, templateArgNames, resultTypeDef, resultValueExpansion);
+
+        if (argCount < Constants.MaxResultTupleSize)
+        {
+            GenerateExpandedMethods(sb, templateArgNames, resultTypeDef, resultValueExpansion);
+            GenerateExpandedAsyncMethods("Task", sb, templateArgNames, resultTypeDef, resultValueExpansion);
+            GenerateExpandedAsyncMethods("ValueTask", sb, templateArgNames, resultTypeDef, resultValueExpansion);
+        }
+
+        sb.AppendLine("#endregion");
+    }
+
+    private void GenerateAsyncMethods(string taskType, StringBuilder sb, ImmutableArray<string> templateArgNames, string resultTypeDef, string resultValueExpansion)
+    {
+        string methodTemplateDecl = GenerateTemplateDecl(templateArgNames);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultTypeDef}}> Append{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func<Result> nextFunc)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            if (result.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(result));
+            }
+            else if (result.IsFailure)
+            {
+                return result.Error!;
+            }
+
+            var next = nextFunc();
+            if (next.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(nextFunc));
+            }
+            else if (next.IsFailure)
+            {
+                return next.Error!;
+            }
+
+            return Result.Success({{resultValueExpansion}});
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultTypeDef}}> Append{{methodTemplateDecl}}(this {{resultTypeDef}} result, Func<{{taskType}}<Result>> nextFunc)
+        {
+            if (result.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(result));
+            }
+            else if (result.IsFailure)
+            {
+                return result.Error!;
+            }
+
+            var next = await nextFunc().ConfigureAwait(false);
+            if (next.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(nextFunc));
+            }
+            else if (next.IsFailure)
+            {
+                return next.Error!;
+            }
+
+            return Result.Success({{resultValueExpansion}});
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultTypeDef}}> Append{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func<{{taskType}}<Result>> nextFunc)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            if (result.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(resultTask));
+            }
+            else if (result.IsFailure)
+            {
+                return result.Error!;
+            }
+
+            var next = await nextFunc().ConfigureAwait(false);
+            if (next.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(nextFunc));
+            }
+            else if (next.IsFailure)
+            {
+                return next.Error!;
+            }
+
+            return Result.Success({{resultValueExpansion}});
+        }
+        """);
+    }
+
+    private void GenerateExpandedAsyncMethods(string taskType, StringBuilder sb, ImmutableArray<string> templateArgNames, string resultTypeDef, string resultValueExpansion)
+    {
+        var expandedTemplateArgNames = templateArgNames.Add("TNext");
+        string resultExpandedTypeDef = GenerateResultTypeDef(expandedTemplateArgNames);
+        string methodExpandedTemplateDecl = GenerateTemplateDecl(expandedTemplateArgNames);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultExpandedTypeDef}}> Append{{methodExpandedTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, TNext next)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            return result.State switch
+            {
+                ResultState.Success => Result.Success({{JoinArguments(resultValueExpansion, "next")}}),
+                ResultState.Error => result.Error!,
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultExpandedTypeDef}}> Append{{methodExpandedTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Result<TNext> next)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            if ((result.State & next.State) == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
+            }
+
+            Error? error = null;
+            if (result.IsFailure)
+            {
+                error += result.Error;
+            }
+            if (next.IsFailure)
+            {
+                error += next.Error;
+            }
+
+            return error is null
+                ? Result.Success({{JoinArguments(resultValueExpansion, "next.Value")}})
+                : error;
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultExpandedTypeDef}}> Append{{methodExpandedTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func<TNext> nextFunc)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            return result.State switch
+            {
+                ResultState.Success => Result.Success({{JoinArguments(resultValueExpansion, "nextFunc()")}}),
+                ResultState.Error => result.Error!,
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultExpandedTypeDef}}> Append{{methodExpandedTemplateDecl}}(this {{resultTypeDef}} result, Func<{{taskType}}<TNext>> nextFunc)
+        {
+            return result.State switch
+            {
+                ResultState.Success => Result.Success({{JoinArguments(resultValueExpansion, "await nextFunc().ConfigureAwait(false)")}}),
+                ResultState.Error => result.Error!,
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultExpandedTypeDef}}> Append{{methodExpandedTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func<{{taskType}}<TNext>> nextFunc)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            return result.State switch
+            {
+                ResultState.Success => Result.Success({{JoinArguments(resultValueExpansion, "await nextFunc().ConfigureAwait(false)")}}),
+                ResultState.Error => result.Error!,
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultExpandedTypeDef}}> Append{{methodExpandedTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func<Result<TNext>> nextFunc)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            if (result.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(resultTask));
+            }
+            else if (result.IsFailure)
+            {
+                return result.Error!;
+            }
+
+            var next = nextFunc();
+            if (next.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(nextFunc));
+            }
+            else if (next.IsFailure)
+            {
+                return next.Error!;
+            }
+
+            return Result.Success({{JoinArguments(resultValueExpansion, "next.Value")}});
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultExpandedTypeDef}}> Append{{methodExpandedTemplateDecl}}(this {{resultTypeDef}} result, Func<{{taskType}}<Result<TNext>>> nextFunc)
+        {
+            if (result.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(result));
+            }
+            else if (result.IsFailure)
+            {
+                return result.Error!;
+            }
+
+            var next = await nextFunc().ConfigureAwait(false);
+            if (next.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(nextFunc));
+            }
+            else if (next.IsFailure)
+            {
+                return next.Error!;
+            }
+
+            return Result.Success({{JoinArguments(resultValueExpansion, "next.Value")}});
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultExpandedTypeDef}}> Append{{methodExpandedTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func<{{taskType}}<Result<TNext>>> nextFunc)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            if (result.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(resultTask));
+            }
+            else if (result.IsFailure)
+            {
+                return result.Error!;
+            }
+
+            var next = await nextFunc().ConfigureAwait(false);
+            if (next.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(nextFunc));
+            }
+            else if (next.IsFailure)
+            {
+                return next.Error!;
+            }
+
+            return Result.Success({{JoinArguments(resultValueExpansion, "next.Value")}});
+        }
+        """);
+    }
+
+    private static void GenerateExpandedMethods(StringBuilder sb, ImmutableArray<string> templateArgNames, string resultTypeDef, string resultValueExpansion)
+    {
+        var expandedTemplateArgNames = templateArgNames.Add("TNext");
+        string resultExpandedTypeDef = GenerateResultTypeDef(expandedTemplateArgNames);
+        string methodExpandedTemplateDecl = GenerateTemplateDecl(expandedTemplateArgNames);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static {{resultExpandedTypeDef}} Append{{methodExpandedTemplateDecl}}(this in {{resultTypeDef}} result, TNext next)
+        {
+            return result.State switch
+            {
+                ResultState.Success => Result.Success({{JoinArguments(resultValueExpansion, "next")}}),
+                ResultState.Error => result.Error!,
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static {{resultExpandedTypeDef}} Append{{methodExpandedTemplateDecl}}(this in {{resultTypeDef}} result, Func<TNext> nextFunc)
+        {
+            return result.State switch
+            {
+                ResultState.Success => Result.Success({{JoinArguments(resultValueExpansion, "nextFunc()")}}),
+                ResultState.Error => result.Error!,
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static {{resultExpandedTypeDef}} Append{{methodExpandedTemplateDecl}}(this in {{resultTypeDef}} result, Result<TNext> next)
+        {
+            Error? error = null;
+            if ((result.State & next.State) == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
+            }
+
+            if (result.IsFailure)
+            {
+                error += result.Error;
+            }
+            if (next.IsFailure)
+            {
+                error += next.Error;
+            }
+
+            return error is null
+                ? Result.Success({{JoinArguments(resultValueExpansion, "next.Value")}})
+                : error;
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultAppendExecutor)}}", "1.0.0.0")]
+        public static {{resultExpandedTypeDef}} Append{{methodExpandedTemplateDecl}}(this in {{resultTypeDef}} result, Func<Result<TNext>> nextFunc)
+        {
+            if (result.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(result));
+            }
+            else if (result.IsFailure)
+            {
+                return result.Error!;
+            }
+
+            var next = nextFunc();
+            if (next.State == ResultState.Bottom)
+            {
+                throw new ResultNotInitializedException(nameof(nextFunc));
+            }
+            else if (next.IsFailure)
+            {
+                return next.Error!;
+            }
+
+            return Result.Success({{JoinArguments(resultValueExpansion, "next.Value")}});
+        }
+        """);
+    }
+
+    internal static string JoinArguments(string arg1, string arg2) => (arg1, arg2) switch
+    {
+        ("", "") => "",
+        (string arg, "") => arg,
+        ("", string arg) => arg,
+        _ => $"{arg1}, {arg2}"
+    };
+}

Railway.SourceGenerator/ResultBindExecutor.cs

@@ -14,17 +14,18 @@ internal sealed class ResultBindExecutor : ResultExtensionsExecutor
         var templateArgNames = Enumerable.Range(1, argCount)
             .Select(i => $"T{i}")
             .ToImmutableArray();
-        string separatedTemplateArgs = string.Join(", ", templateArgNames);
 
-        sb.AppendLine($"#region <{separatedTemplateArgs}>");
+        string resultTypeDef = GenerateResultTypeDef(templateArgNames);
-
-        string resultValueType = templateArgNames.Length == 1 ? separatedTemplateArgs : $"({separatedTemplateArgs})";
         string resultValueExpansion = GenerateResultValueExpansion(templateArgNames);
+        string methodTemplateDecl = GenerateTemplateDecl(templateArgNames.Add("R"));
+        string bindTemplateDecl = GenerateTemplateDecl(templateArgNames.Add("Result<R>"));
+
+        sb.AppendLine($"#region {resultTypeDef}");
 
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultBindExecutor)}}", "1.0.0.0")]
-        public static Result<R> Bind<{{separatedTemplateArgs}}, R>(this in Result<{{resultValueType}}> result, Func<{{separatedTemplateArgs}}, Result<R>> binding)
+        public static Result<R> Bind{{methodTemplateDecl}}(this in {{resultTypeDef}} result, Func{{bindTemplateDecl}} binding)
         {
             return result.State switch
             {
@@ -35,24 +36,22 @@ internal sealed class ResultBindExecutor : ResultExtensionsExecutor
         }
         """);
 
-        sb.AppendLine($$"""
+        GenerateAsyncMethods("Task", sb, templateArgNames, resultTypeDef, resultValueExpansion);
-        [PureAttribute]
+        GenerateAsyncMethods("ValueTask", sb, templateArgNames, resultTypeDef, resultValueExpansion);
-        [GeneratedCodeAttribute("{{nameof(ResultBindExecutor)}}", "1.0.0.0")]
+
-        public static Task<Result<R>> Bind<{{separatedTemplateArgs}}, R>(this in Result<{{resultValueType}}> result, Func<{{separatedTemplateArgs}}, Task<Result<R>>> binding)
+        sb.AppendLine("#endregion");
-        {
-            return result.State switch
-            {
-                ResultState.Success => binding({{resultValueExpansion}}),
-                ResultState.Error => Task.FromResult<Result<R>>(result.Error!),
-                _ => throw new ResultNotInitializedException(nameof(result))
-            };
     }
-        """);
+
+    private static void GenerateAsyncMethods(string taskType, StringBuilder sb, ImmutableArray<string> templateArgNames, string resultTypeDef, string resultValueExpansion)
+    {
+        string methodTemplateDecl = GenerateTemplateDecl(templateArgNames.Add("R"));
+        string bindTemplateDecl = GenerateTemplateDecl(templateArgNames.Add("Result<R>"));
+        string asyncActionTemplateDecl = GenerateTemplateDecl(templateArgNames.Add($"{taskType}<Result<R>>"));
 
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultBindExecutor)}}", "1.0.0.0")]
-        public static async Task<Result<R>> Bind<{{separatedTemplateArgs}}, R>(this Task<Result<{{resultValueType}}>> resultTask, Func<{{separatedTemplateArgs}}, Result<R>> binding)
+        public static async {{taskType}}<Result<R>> Bind{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func{{bindTemplateDecl}} binding)
         {
             var result = await resultTask.ConfigureAwait(false);
             return result.State switch
@@ -67,7 +66,21 @@ internal sealed class ResultBindExecutor : ResultExtensionsExecutor
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultBindExecutor)}}", "1.0.0.0")]
-        public static async Task<Result<R>> Bind<{{separatedTemplateArgs}}, R>(this Task<Result<{{resultValueType}}>> resultTask, Func<{{separatedTemplateArgs}}, Task<Result<R>>> binding)
+        public static {{taskType}}<Result<R>> Bind{{methodTemplateDecl}}(this in {{resultTypeDef}} result, Func{{asyncActionTemplateDecl}} binding)
+        {
+            return result.State switch
+            {
+                ResultState.Success => binding({{resultValueExpansion}}),
+                ResultState.Error => {{taskType}}.FromResult<Result<R>>(result.Error!),
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultBindExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<Result<R>> Bind{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func{{asyncActionTemplateDecl}} binding)
         {
             var result = await resultTask.ConfigureAwait(false);
             return result.State switch
@@ -78,7 +91,5 @@ internal sealed class ResultBindExecutor : ResultExtensionsExecutor
             };
         }
         """);
-
-        sb.AppendLine("#endregion");
     }
 }

Railway.SourceGenerator/ResultCombineExecutor.cs

@@ -49,10 +49,19 @@ internal sealed class ResultCombineExecutor : IGeneratorExecutor
 
         GenerateGetBottomMethod(sb, argCount);
 
-        var argsResultTupleSizes = new List<ImmutableArray<int>>();
+        var permutations = 1 << argCount;
-        Span<int> templateCounts = stackalloc int[argCount];
+        var argsResultTupleSizes = new ImmutableArray<int>[permutations];
 
-        Permute(templateCounts, argsResultTupleSizes);
+        Span<int> templateCounts = stackalloc int[argCount];
+        for (int i = 0; i < permutations; i++)
+        {
+            templateCounts.Fill(0);
+            for (int j = 0; j < argCount; j++)
+            {
+                templateCounts[j] = (i & (1 << j)) > 0 ? 1 : 0;
+            }
+            argsResultTupleSizes[i] = templateCounts.ToImmutableArray();
+        }
 
         foreach (var argResultTupleSizes in argsResultTupleSizes)
         {
@@ -61,23 +70,6 @@ internal sealed class ResultCombineExecutor : IGeneratorExecutor
 
         sb.AppendLine("#endregion");
 
-        static void Permute(Span<int> templateCounts, ICollection<ImmutableArray<int>> argsResultTupleSizes, int lvl = 0)
-        {
-            int sum = 0;
-            for (int i = 0; i < lvl; i++)
-            {
-                sum += templateCounts[i];
-            }
-            for (templateCounts[lvl] = 0; templateCounts[lvl] <= Constants.MaxResultTupleSize - sum; templateCounts[lvl]++)
-            {
-                if (lvl == templateCounts.Length - 1)
-                {
-                    argsResultTupleSizes.Add(templateCounts.ToImmutableArray());
-                    continue;
-                }
-                Permute(templateCounts, argsResultTupleSizes, lvl + 1);
-            }
-        }
     }
 
     private static void GenerateGetBottomMethod(StringBuilder sb, int argCount)

Railway.SourceGenerator/ResultExtensionsExecutor.cs

@@ -31,7 +31,8 @@ internal abstract class ResultExtensionsExecutor : IGeneratorExecutor
     {
         var sb = new StringBuilder();
 
-        for (int i = 1; i <= Constants.MaxResultTupleSize; i++)
+        GenerateHelperMethods(sb);
+        for (int i = 0; i <= Constants.MaxResultTupleSize; i++)
         {
             GenerateMethodsForArgCount(sb, argCount: i);
         }
@@ -39,11 +40,32 @@ internal abstract class ResultExtensionsExecutor : IGeneratorExecutor
         return sb.ToString();
     }
 
-    protected string GenerateResultValueExpansion(ImmutableArray<string> templateArgNames)
+    protected static string GenerateTemplateDecl(ImmutableArray<string> templateArgNames) => templateArgNames.Length > 0
+        ? $"<{string.Join(", ", templateArgNames)}>"
+        : string.Empty;
+
+    protected static string GenerateResultTypeDef(ImmutableArray<string> templateArgNames) => templateArgNames.Length switch
+        {
+            0 => "Result",
+            1 => $"Result<{string.Join(", ", templateArgNames)}>",
+            _ => $"Result<({string.Join(", ", templateArgNames)})>",
+        };
+
+    protected static string GenerateResultValueExpansion(ImmutableArray<string> templateArgNames)
     {
         string resultExpansion;
-        if (templateArgNames.Length > 1)
+
+        switch (templateArgNames.Length)
         {
+            case 0:
+            resultExpansion = string.Empty;
+            break;
+
+            case 1:
+            resultExpansion = "result.Value";
+            break;
+
+            default:
             var resultExpansionBuilder = new StringBuilder();
             for (int i = 1; i <= templateArgNames.Length; i++)
             {
@@ -51,10 +73,7 @@ internal abstract class ResultExtensionsExecutor : IGeneratorExecutor
             }
             resultExpansionBuilder.Remove(resultExpansionBuilder.Length - 2, 2);
             resultExpansion = resultExpansionBuilder.ToString();
-        }
+            break;
-        else
-        {
-            resultExpansion = "result.Value";
         }
 
         return resultExpansion;
@@ -62,4 +81,5 @@ internal abstract class ResultExtensionsExecutor : IGeneratorExecutor
 
     protected abstract string ExtensionType { get; }
     protected abstract void GenerateMethodsForArgCount(StringBuilder sb, int argCount);
+    protected virtual void GenerateHelperMethods(StringBuilder sb) {}
 }

Railway.SourceGenerator/ResultMapExecutor.cs

@@ -13,17 +13,17 @@ internal sealed class ResultMapExecutor : ResultExtensionsExecutor
         var templateArgNames = Enumerable.Range(1, argCount)
             .Select(i => $"T{i}")
             .ToImmutableArray();
-        string separatedTemplateArgs = string.Join(", ", templateArgNames);
 
-        sb.AppendLine($"#region <{separatedTemplateArgs}>");
+        string resultTypeDef = GenerateResultTypeDef(templateArgNames);
-
-        string resultValueType = templateArgNames.Length == 1 ? separatedTemplateArgs : $"({separatedTemplateArgs})";
         string resultValueExpansion = GenerateResultValueExpansion(templateArgNames);
+        string methodTemplateDecl = GenerateTemplateDecl(templateArgNames.Add("R"));
+
+        sb.AppendLine($"#region {resultTypeDef}");
 
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultMapExecutor)}}", "1.0.0.0")]
-        public static Result<R> Map<{{separatedTemplateArgs}}, R>(this in Result<{{resultValueType}}> result, Func<{{separatedTemplateArgs}}, R> mapping)
+        public static Result<R> Map{{methodTemplateDecl}}(this in {{resultTypeDef}} result, Func{{methodTemplateDecl}} mapping)
         {
             return result.State switch
             {
@@ -34,50 +34,60 @@ internal sealed class ResultMapExecutor : ResultExtensionsExecutor
         }
         """);
 
-        sb.AppendLine($$"""
+        GenerateAsyncMethods("Task", sb, templateArgNames, resultTypeDef, resultValueExpansion);
-        [PureAttribute]
+        GenerateAsyncMethods("ValueTask", sb, templateArgNames, resultTypeDef, resultValueExpansion);
-        [GeneratedCodeAttribute("{{nameof(ResultMapExecutor)}}", "1.0.0.0")]
-        public static async Task<Result<R>> Map<{{separatedTemplateArgs}}, R>(this Result<{{resultValueType}}> result, Func<{{separatedTemplateArgs}}, Task<R>> mapping)
-        {
-            return result.State switch
-            {
-                ResultState.Success => await mapping({{resultValueExpansion}}).ConfigureAwait(false),
-                ResultState.Error => result.Error!,
-                _ => throw new ResultNotInitializedException(nameof(result))
-            };
-        }
-        """);
-
-        sb.AppendLine($$"""
-        [PureAttribute]
-        [GeneratedCodeAttribute("{{nameof(ResultMapExecutor)}}", "1.0.0.0")]
-        public static async Task<Result<R>> Map<{{separatedTemplateArgs}}, R>(this Task<Result<{{resultValueType}}>> resultTask, Func<{{separatedTemplateArgs}}, R> mapping)
-        {
-            var result = await resultTask.ConfigureAwait(false);
-            return result.State switch
-            {
-                ResultState.Success => mapping({{resultValueExpansion}}),
-                ResultState.Error => result.Error!,
-                _ => throw new ResultNotInitializedException(nameof(resultTask))
-            };
-        }
-        """);
-
-        sb.AppendLine($$"""
-        [PureAttribute]
-        [GeneratedCodeAttribute("{{nameof(ResultMapExecutor)}}", "1.0.0.0")]
-        public static async Task<Result<R>> Map<{{separatedTemplateArgs}}, R>(this Task<Result<{{resultValueType}}>> resultTask, Func<{{separatedTemplateArgs}}, Task<R>> mapping)
-        {
-            var result = await resultTask.ConfigureAwait(false);
-            return result.State switch
-            {
-                ResultState.Success => await mapping({{resultValueExpansion}}).ConfigureAwait(false),
-                ResultState.Error => result.Error!,
-                _ => throw new ResultNotInitializedException(nameof(resultTask))
-            };
-        }
-        """);
 
         sb.AppendLine("#endregion");
     }
+
+    private static void GenerateAsyncMethods(string taskType, StringBuilder sb, ImmutableArray<string> templateArgNames, string resultTypeDef, string resultValueExpansion)
+    {
+        var methodTemplateArgNames = templateArgNames.Add("R");
+        string methodTemplateDecl = GenerateTemplateDecl(methodTemplateArgNames);
+        string asyncActionTemplateDecl = GenerateTemplateDecl(templateArgNames.Add($"{taskType}<R>"));
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultMapExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<Result<R>> Map{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func{{methodTemplateDecl}} mapping)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            return result.State switch
+            {
+                ResultState.Success => mapping({{resultValueExpansion}}),
+                ResultState.Error => result.Error!,
+                _ => throw new ResultNotInitializedException(nameof(resultTask))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultMapExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<Result<R>> Map{{methodTemplateDecl}}(this {{resultTypeDef}} result, Func{{asyncActionTemplateDecl}} mapping)
+        {
+            return result.State switch
+            {
+                ResultState.Success => await mapping({{resultValueExpansion}}).ConfigureAwait(false),
+                ResultState.Error => result.Error!,
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultMapExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<Result<R>> Map{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func{{asyncActionTemplateDecl}} mapping)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            return result.State switch
+            {
+                ResultState.Success => await mapping({{resultValueExpansion}}).ConfigureAwait(false),
+                ResultState.Error => result.Error!,
+                _ => throw new ResultNotInitializedException(nameof(resultTask))
+            };
+        }
+        """);
+    }
 }

Railway.SourceGenerator/ResultMatchExecutor.cs

@@ -1,5 +1,3 @@
-using System;
-using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
 using System.Text;
@@ -16,17 +14,17 @@ internal sealed class ResultMatchExecutor : ResultExtensionsExecutor
         var templateArgNames = Enumerable.Range(1, argCount)
             .Select(i => $"T{i}")
             .ToImmutableArray();
-        string separatedTemplateArgs = string.Join(", ", templateArgNames);
 
-        sb.AppendLine($"#region <{separatedTemplateArgs}>");
+        string resultTypeDef = GenerateResultTypeDef(templateArgNames);
-
-        string resultValueType = templateArgNames.Length == 1 ? separatedTemplateArgs : $"({separatedTemplateArgs})";
         string resultValueExpansion = GenerateResultValueExpansion(templateArgNames);
+        string methodTemplateDecl = GenerateTemplateDecl(templateArgNames.Add("R"));
+
+        sb.AppendLine($"#region {resultTypeDef}");
 
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultMatchExecutor)}}", "1.0.0.0")]
-        public static R Match<{{separatedTemplateArgs}}, R>(this in Result<{{resultValueType}}> result, Func<{{separatedTemplateArgs}}, R> onSuccess, Func<Error, R> onFailure)
+        public static R Match{{methodTemplateDecl}}(this in {{resultTypeDef}} result, Func{{methodTemplateDecl}} onSuccess, Func<Error, R> onFailure)
         {
             return result.State switch
             {
@@ -37,24 +35,22 @@ internal sealed class ResultMatchExecutor : ResultExtensionsExecutor
         }
         """);
 
-        sb.AppendLine($$"""
+        GenerateAsyncMethods("Task", sb, templateArgNames, resultTypeDef, resultValueExpansion);
-        [PureAttribute]
+        GenerateAsyncMethods("ValueTask", sb, templateArgNames, resultTypeDef, resultValueExpansion);
-        [GeneratedCodeAttribute("{{nameof(ResultMatchExecutor)}}", "1.0.0.0")]
+
-        public static Task<R> Match<{{separatedTemplateArgs}}, R>(this in Result<{{resultValueType}}> result, Func<{{separatedTemplateArgs}}, Task<R>> onSuccess, Func<Error, Task<R>> onFailure)
+        sb.AppendLine("#endregion");
-        {
-            return result.State switch
-            {
-                ResultState.Success => onSuccess({{resultValueExpansion}}),
-                ResultState.Error => onFailure(result.Error!),
-                _ => throw new ResultNotInitializedException(nameof(result))
-            };
     }
-        """);
+
+    private static void GenerateAsyncMethods(string taskType, StringBuilder sb, ImmutableArray<string> templateArgNames, string resultTypeDef, string resultValueExpansion)
+    {
+        var methodTemplateArgNames = templateArgNames.Add("R");
+        string methodTemplateDecl = GenerateTemplateDecl(methodTemplateArgNames);
+        string asyncActionTemplateDecl = GenerateTemplateDecl(templateArgNames.Add($"{taskType}<R>"));
 
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultMatchExecutor)}}", "1.0.0.0")]
-        public static async Task<R> Match<{{separatedTemplateArgs}}, R>(this Task<Result<{{resultValueType}}>> resultTask, Func<{{separatedTemplateArgs}}, R> onSuccess, Func<Error, R> onFailure)
+        public static async {{taskType}}<R> Match{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func{{methodTemplateDecl}} onSuccess, Func<Error, R> onFailure)
         {
             var result = await resultTask.ConfigureAwait(false);
             return result.State switch
@@ -69,7 +65,21 @@ internal sealed class ResultMatchExecutor : ResultExtensionsExecutor
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultMatchExecutor)}}", "1.0.0.0")]
-        public static async Task<R> Match<{{separatedTemplateArgs}}, R>(this Task<Result<{{resultValueType}}>> resultTask, Func<{{separatedTemplateArgs}}, Task<R>> onSuccess, Func<Error, Task<R>> onFailure)
+        public static {{taskType}}<R> Match{{methodTemplateDecl}}(this in {{resultTypeDef}} result, Func{{asyncActionTemplateDecl}} onSuccess, Func<Error, {{taskType}}<R>> onFailure)
+        {
+            return result.State switch
+            {
+                ResultState.Success => onSuccess({{resultValueExpansion}}),
+                ResultState.Error => onFailure(result.Error!),
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultMatchExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<R> Match{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func{{asyncActionTemplateDecl}} onSuccess, Func<Error, {{taskType}}<R>> onFailure)
         {
             var result = await resultTask.ConfigureAwait(false);
             var matchTask = result.State switch
@@ -81,7 +91,5 @@ internal sealed class ResultMatchExecutor : ResultExtensionsExecutor
             return await matchTask.ConfigureAwait(false);
         }
         """);
-
-        sb.AppendLine("#endregion");
     }
 }

Railway.SourceGenerator/ResultTapExecutor.cs

@@ -14,17 +14,17 @@ internal sealed class ResultTapExecutor : ResultExtensionsExecutor
         var templateArgNames = Enumerable.Range(1, argCount)
             .Select(i => $"T{i}")
             .ToImmutableArray();
-        string separatedTemplateArgs = string.Join(", ", templateArgNames);
 
-        sb.AppendLine($"#region <{separatedTemplateArgs}>");
+        string methodTemplateDecl = GenerateTemplateDecl(templateArgNames);
-
+        string resultTypeDef = GenerateResultTypeDef(templateArgNames);
-        string resultValueType = templateArgNames.Length == 1 ? separatedTemplateArgs : $"({separatedTemplateArgs})";
         string resultValueExpansion = GenerateResultValueExpansion(templateArgNames);
 
+        sb.AppendLine($"#region {resultTypeDef}");
+
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultTapExecutor)}}", "1.0.0.0")]
-        public static ref readonly Result<{{resultValueType}}> Tap<{{separatedTemplateArgs}}>(this in Result<{{resultValueType}}> result, Action<{{separatedTemplateArgs}}>? onSuccess = null, Action<Error>? onFailure = null)
+        public static ref readonly {{resultTypeDef}} Tap{{methodTemplateDecl}}(this in {{resultTypeDef}} result, Action{{methodTemplateDecl}}? onSuccess = null, Action<Error>? onFailure = null)
         {
             switch (result.State)
             {
@@ -41,10 +41,21 @@ internal sealed class ResultTapExecutor : ResultExtensionsExecutor
         }
         """);
 
+        GenerateAsyncMethods("Task", sb, templateArgNames, resultTypeDef, resultValueExpansion);
+        GenerateAsyncMethods("ValueTask", sb, templateArgNames, resultTypeDef, resultValueExpansion);
+
+        sb.AppendLine("#endregion");
+    }
+
+    private static void GenerateAsyncMethods(string taskType, StringBuilder sb, ImmutableArray<string> templateArgNames, string resultTypeDef, string resultValueExpansion)
+    {
+        string methodTemplateDecl = GenerateTemplateDecl(templateArgNames);
+        string asyncActionTemplateDecl = GenerateTemplateDecl(templateArgNames.Add(taskType));
+
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultTapExecutor)}}", "1.0.0.0")]
-        public static async Task<Result<{{resultValueType}}>> Tap<{{separatedTemplateArgs}}>(this Task<Result<{{resultValueType}}>> resultTask, Action<{{separatedTemplateArgs}}>? onSuccess = null, Action<Error>? onFailure = null)
+        public static async {{taskType}}<{{resultTypeDef}}> Tap{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Action{{methodTemplateDecl}}? onSuccess = null, Action<Error>? onFailure = null)
         {
             var result = await resultTask.ConfigureAwait(false);
             switch (result.State)
@@ -65,7 +76,7 @@ internal sealed class ResultTapExecutor : ResultExtensionsExecutor
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultTapExecutor)}}", "1.0.0.0")]
-        public static async Task<Result<{{resultValueType}}>> Tap<{{separatedTemplateArgs}}>(this Result<{{resultValueType}}> result, Func<{{separatedTemplateArgs}}, Task>? onSuccess = null, Func<Error, Task>? onFailure = null)
+        public static async {{taskType}}<{{resultTypeDef}}> Tap{{methodTemplateDecl}}(this {{resultTypeDef}} result, Func{{asyncActionTemplateDecl}}? onSuccess = null, Func<Error, {{taskType}}>? onFailure = null)
         {
             switch (result.State)
             {
@@ -87,7 +98,7 @@ internal sealed class ResultTapExecutor : ResultExtensionsExecutor
         sb.AppendLine($$"""
         [PureAttribute]
         [GeneratedCodeAttribute("{{nameof(ResultTapExecutor)}}", "1.0.0.0")]
-        public static async Task<Result<{{resultValueType}}>> Tap<{{separatedTemplateArgs}}>(this Task<Result<{{resultValueType}}>> resultTask, Func<{{separatedTemplateArgs}}, Task>? onSuccess = null, Func<Error, Task>? onFailure = null)
+        public static async {{taskType}}<{{resultTypeDef}}> Tap{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func{{asyncActionTemplateDecl}}? onSuccess = null, Func<Error, {{taskType}}>? onFailure = null)
         {
             var result = await resultTask.ConfigureAwait(false);
             switch (result.State)
@@ -106,7 +117,5 @@ internal sealed class ResultTapExecutor : ResultExtensionsExecutor
             return result;
         }
         """);
-
-        sb.AppendLine("#endregion");
     }
 }

Railway.SourceGenerator/ResultTryRecoverExecutor.cs

@@ -0,0 +1,85 @@
+using System.Collections.Immutable;
+using System.Linq;
+using System.Text;
+
+namespace Just.Railway.SourceGen;
+
+internal sealed class ResultTryRecoverExecutor : ResultExtensionsExecutor
+{
+    protected override string ExtensionType => "TryRecover";
+    protected override void GenerateMethodsForArgCount(StringBuilder sb, int argCount)
+    {
+        if (argCount > 1) return;
+        
+        var templateArgNames = Enumerable.Repeat("T", argCount)
+            .ToImmutableArray();
+
+        string methodTemplateDecl = GenerateTemplateDecl(templateArgNames);
+        string resultTypeDef = GenerateResultTypeDef(templateArgNames);
+
+        sb.AppendLine($"#region {resultTypeDef}");
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTryRecoverExecutor)}}", "1.0.0.0")]
+        public static {{resultTypeDef}} TryRecover{{methodTemplateDecl}}(this in {{resultTypeDef}} result, Func<Error, {{resultTypeDef}}> recover)
+        {
+            return result.State switch
+            {
+                ResultState.Success => ({{resultTypeDef}})result.Value,
+                ResultState.Error => recover(result.Error!),
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+
+        GenerateAsyncMethods("Task", sb, templateArgNames, resultTypeDef, methodTemplateDecl);
+        GenerateAsyncMethods("ValueTask", sb, templateArgNames, resultTypeDef, methodTemplateDecl);
+
+        sb.AppendLine("#endregion");
+    }
+    private static void GenerateAsyncMethods(string taskType, StringBuilder sb, ImmutableArray<string> templateArgNames, string resultTypeDef, string methodTemplateDecl)
+    {
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTryRecoverExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultTypeDef}}> TryRecover{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func<Error, {{resultTypeDef}}> recover)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            return result.State switch
+            {
+                ResultState.Success => ({{resultTypeDef}})result.Value,
+                ResultState.Error => recover(result.Error!),
+                _ => throw new ResultNotInitializedException(nameof(resultTask))
+            };
+        }
+        """);
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTryRecoverExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultTypeDef}}> TryRecover{{methodTemplateDecl}}(this {{resultTypeDef}} result, Func<Error, {{taskType}}<{{resultTypeDef}}>> recover)
+        {
+            return result.State switch
+            {
+                ResultState.Success => ({{resultTypeDef}})result.Value,
+                ResultState.Error => await recover(result.Error!).ConfigureAwait(false),
+                _ => throw new ResultNotInitializedException(nameof(result))
+            };
+        }
+        """);
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTryRecoverExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<{{resultTypeDef}}> TryRecover{{methodTemplateDecl}}(this {{taskType}}<{{resultTypeDef}}> resultTask, Func<Error, {{taskType}}<{{resultTypeDef}}>> recover)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            return result.State switch
+            {
+                ResultState.Success => ({{resultTypeDef}})result.Value,
+                ResultState.Error => await recover(result.Error!).ConfigureAwait(false),
+                _ => throw new ResultNotInitializedException(nameof(resultTask))
+            };
+        }
+        """);
+    }
+}

Railway.SourceGenerator/TryExtensionsExecutor.cs

@@ -0,0 +1,210 @@
+using System.Collections.Immutable;
+using System.Linq;
+using System.Text;
+using Microsoft.CodeAnalysis;
+
+namespace Just.Railway.SourceGen;
+
+public sealed class TryExtensionsExecutor : IGeneratorExecutor
+{
+    public void Execute(SourceProductionContext context, Compilation source)
+    {
+        var methods = GenerateMethods();
+        var code = $$"""
+        #nullable enable
+        using System;
+        using System.Collections.Generic;
+        using System.Diagnostics.Contracts;
+        using System.CodeDom.Compiler;
+
+        namespace Just.Railway;
+
+        public static partial class Try
+        {
+        {{methods}}
+        }
+        """;
+
+        context.AddSource("Try.Run.g.cs", code);
+    }
+
+    private string GenerateMethods()
+    {
+        var sb = new StringBuilder();
+
+        for (int i = 0; i <= Constants.MaxResultTupleSize; i++)
+        {
+            GenerateMethodsForArgCount(sb, argCount: i);
+        }
+
+        return sb.ToString();
+    }
+
+    private void GenerateMethodsForArgCount(StringBuilder sb, int argCount)
+    {
+        var templateArgNames = Enumerable.Range(1, argCount)
+            .Select(i => $"T{i}")
+            .ToImmutableArray();
+        var argNames = Enumerable.Range(1, argCount)
+            .Select(i => $"arg{i}")
+            .ToImmutableArray();
+
+        string actionTemplateDecl = GenerateTemplateDecl(templateArgNames);
+        string resultActionTemplateDecl = GenerateTemplateDecl(templateArgNames.Add("Result"));
+        string funcTemplateDecl = GenerateTemplateDecl(templateArgNames.Add("TResult"));
+        string resultFuncTemplateDecl = GenerateTemplateDecl(templateArgNames.Add("Result<TResult>"));
+        string argumentsDeclExpansion = string.Join(", ", templateArgNames.Zip(argNames, (t, n) => $"{t} {n}"));
+        string argumentsExpansion = string.Join(", ", argNames);
+
+        sb.AppendLine($"#region <{string.Join(", ", templateArgNames)}>");
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(TryExtensionsExecutor)}}", "1.0.0.0")]
+        public static Result Run{{actionTemplateDecl}}(Action{{actionTemplateDecl}} action{{TrailingArguments(argumentsDeclExpansion)}})
+        {
+            try
+            {
+                action({{argumentsExpansion}});
+                return Result.Success();
+            }
+            catch (Exception ex)
+            {
+                return Error.New(ex);
+            }
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(TryExtensionsExecutor)}}", "1.0.0.0")]
+        public static Result Run{{actionTemplateDecl}}(Func{{resultActionTemplateDecl}} action{{TrailingArguments(argumentsDeclExpansion)}})
+        {
+            try
+            {
+                return action({{argumentsExpansion}});
+            }
+            catch (Exception ex)
+            {
+                return Error.New(ex);
+            }
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(TryExtensionsExecutor)}}", "1.0.0.0")]
+        public static Result<TResult> Run{{funcTemplateDecl}}(Func{{funcTemplateDecl}} func{{TrailingArguments(argumentsDeclExpansion)}})
+        {
+            try
+            {
+                return Result.Success(func({{argumentsExpansion}}));
+            }
+            catch (Exception ex)
+            {
+                return Error.New(ex);
+            }
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(TryExtensionsExecutor)}}", "1.0.0.0")]
+        public static Result<TResult> Run{{funcTemplateDecl}}(Func{{resultFuncTemplateDecl}} func{{TrailingArguments(argumentsDeclExpansion)}})
+        {
+            try
+            {
+                return func({{argumentsExpansion}});
+            }
+            catch (Exception ex)
+            {
+                return Error.New(ex);
+            }
+        }
+        """);
+
+        GenerateAsyncMethods(sb, templateArgNames, actionTemplateDecl, funcTemplateDecl, argumentsDeclExpansion, argumentsExpansion, "Task");
+        GenerateAsyncMethods(sb, templateArgNames, actionTemplateDecl, funcTemplateDecl, argumentsDeclExpansion, argumentsExpansion, "ValueTask");
+
+        sb.AppendLine("#endregion");
+    }
+
+    private static void GenerateAsyncMethods(StringBuilder sb, ImmutableArray<string> templateArgNames, string actionTemplateDecl, string funcTemplateDecl, string argumentsDeclExpansion, string argumentsExpansion, string taskType)
+    {
+        string actionTaskTemplateDecl = GenerateTemplateDecl(templateArgNames.Add(taskType));
+        string resultActionTaskTemplateDecl = GenerateTemplateDecl(templateArgNames.Add($"{taskType}<Result>"));
+        string funcTaskTemplateDecl = GenerateTemplateDecl(templateArgNames.Add($"{taskType}<TResult>"));
+        string resultFuncTaskTemplateDecl = GenerateTemplateDecl(templateArgNames.Add($"{taskType}<Result<TResult>>"));
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(TryExtensionsExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<Result> Run{{actionTemplateDecl}}(Func{{actionTaskTemplateDecl}} action{{TrailingArguments(argumentsDeclExpansion)}})
+        {
+            try
+            {
+                await action({{argumentsExpansion}}).ConfigureAwait(false);
+                return Result.Success();
+            }
+            catch (Exception ex)
+            {
+                return Error.New(ex);
+            }
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(TryExtensionsExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<Result> Run{{actionTemplateDecl}}(Func{{resultActionTaskTemplateDecl}} action{{TrailingArguments(argumentsDeclExpansion)}})
+        {
+            try
+            {
+                return await action({{argumentsExpansion}}).ConfigureAwait(false);
+            }
+            catch (Exception ex)
+            {
+                return Error.New(ex);
+            }
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(TryExtensionsExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<Result<TResult>> Run{{funcTemplateDecl}}(Func{{funcTaskTemplateDecl}} func{{TrailingArguments(argumentsDeclExpansion)}})
+        {
+            try
+            {
+                return Result.Success(await func({{argumentsExpansion}}).ConfigureAwait(false));
+            }
+            catch (Exception ex)
+            {
+                return Error.New(ex);
+            }
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(TryExtensionsExecutor)}}", "1.0.0.0")]
+        public static async {{taskType}}<Result<TResult>> Run{{funcTemplateDecl}}(Func{{resultFuncTaskTemplateDecl}} func{{TrailingArguments(argumentsDeclExpansion)}})
+        {
+            try
+            {
+                return await func({{argumentsExpansion}}).ConfigureAwait(false);
+            }
+            catch (Exception ex)
+            {
+                return Error.New(ex);
+            }
+        }
+        """);
+    }
+
+    private static string TrailingArguments(string argumentsExpansion) => string.IsNullOrEmpty(argumentsExpansion)
+        ? string.Empty
+        : $", {argumentsExpansion}";
+    private static string GenerateTemplateDecl(ImmutableArray<string> templateArgNames) => templateArgNames.Length > 0
+        ? $"<{string.Join(", ", templateArgNames)}>"
+        : string.Empty;
+}

Railway/Ensure.cs

@@ -1,296 +1,16 @@
 namespace Just.Railway;
 
-public static class Ensure
+public static partial class Ensure
 {
     public delegate Error ErrorFactory(string valueExpression);
 
     public const string DefaultErrorType = "EnsureFailed";
 
     [Pure] public static Ensure<T> That<T>(T value, [CallerArgumentExpression(nameof(value))]string valueExpression = "") => new(value, valueExpression);
-    [Pure] public static async Task<Ensure<T>> That<T>(Task<T> value, [CallerArgumentExpression(nameof(value))]string valueExpression = "") => new(await value.ConfigureAwait(false), valueExpression);
 
-    [Pure] public static Result<T> Result<T>(this in Ensure<T> ensure) => ensure.State switch
+    [Pure] public static Result<T> Result<T>(this in Ensure<T> ensure) => ensure;
-    {
+    [Pure] public static async Task<Result<T>> Result<T>(this Task<Ensure<T>> ensureTask) => await ensureTask.ConfigureAwait(false);
-        ResultState.Success => new(ensure.Value),
+    [Pure] public static async ValueTask<Result<T>> Result<T>(this ValueTask<Ensure<T>> ensureTask) => await ensureTask.ConfigureAwait(false);
-        ResultState.Error => new(ensure.Error!),
-        _ => throw new EnsureNotInitializedException(nameof(ensure))
-    };
-    [Pure]
-    public static async Task<Result<T>> Result<T>(this Task<Ensure<T>> ensureTask)
-    {
-        var ensure = await ensureTask.ConfigureAwait(false);
-        return ensure.State switch
-        {
-            ResultState.Success => new(ensure.Value),
-            ResultState.Error => new(ensure.Error!),
-            _ => throw new EnsureNotInitializedException(nameof(ensureTask))
-        };
-    }
-    [Pure]
-    public static Ensure<T> Satisfies<T>(this in Ensure<T> ensure, Func<T, bool> requirement, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => requirement(ensure.Value)
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} does not satisfy the requirement."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static Ensure<T> Satisfies<T>(this in Ensure<T> ensure, Func<T, bool> requirement, ErrorFactory errorFactory)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => requirement(ensure.Value)
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(errorFactory(ensure.ValueExpression), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static async Task<Ensure<T>> Satisfies<T>(this Task<Ensure<T>> ensureTask, Func<T, bool> requirement, Error error = default!)
-    {
-        var ensure = await ensureTask.ConfigureAwait(false);
-        return ensure.State switch
-        {
-            ResultState.Success => requirement(ensure.Value)
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} does not satisfy the requirement."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensureTask))
-        };
-    }
-    [Pure]
-    public static async Task<Ensure<T>> Satisfies<T>(this Task<Ensure<T>> ensureTask, Func<T, bool> requirement, ErrorFactory errorFactory)
-    {
-        var ensure = await ensureTask.ConfigureAwait(false);
-        return ensure.State switch
-        {
-            ResultState.Success => requirement(ensure.Value)
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(errorFactory(ensure.ValueExpression), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensureTask))
-        };
-    }
-    [Pure]
-    public static async Task<Ensure<T>> Satisfies<T>(this Ensure<T> ensure, Func<T, Task<bool>> requirement, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => await requirement(ensure.Value).ConfigureAwait(false)
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} does not satisfy the requirement."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static async Task<Ensure<T>> Satisfies<T>(this Ensure<T> ensure, Func<T, Task<bool>> requirement, ErrorFactory errorFactory)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => await requirement(ensure.Value).ConfigureAwait(false)
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(errorFactory(ensure.ValueExpression), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static async Task<Ensure<T>> Satisfies<T>(this Task<Ensure<T>> ensureTask, Func<T, Task<bool>> requirement, Error error = default!)
-    {
-        var ensure = await ensureTask.ConfigureAwait(false);
-        return ensure.State switch
-        {
-            ResultState.Success => await requirement(ensure.Value).ConfigureAwait(false)
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} does not satisfy the requirement."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensureTask))
-        };
-    }
-    [Pure]
-    public static async Task<Ensure<T>> Satisfies<T>(this Task<Ensure<T>> ensureTask, Func<T, Task<bool>> requirement, ErrorFactory errorFactory)
-    {
-        var ensure = await ensureTask.ConfigureAwait(false);
-        return ensure.State switch
-        {
-            ResultState.Success => await requirement(ensure.Value).ConfigureAwait(false)
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(errorFactory(ensure.ValueExpression), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensureTask))
-        };
-    }
-
-    [Pure]
-    public static Ensure<T> NotNull<T>(this in Ensure<T?> ensure, Error error = default!)
-        where T : struct
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => ensure.Value.HasValue
-                ? new(ensure.Value.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is null."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static async Task<Ensure<T>> NotNull<T>(this Task<Ensure<T?>> ensureTask, Error error = default!)
-        where T : struct
-    {
-        var ensure = await ensureTask.ConfigureAwait(false);
-        return ensure.State switch
-        {
-            ResultState.Success => ensure.Value.HasValue
-                ? new(ensure.Value.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is null."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensureTask))
-        };
-    }
-    [Pure]
-    public static Ensure<T> NotNull<T>(this in Ensure<T?> ensure, Error error = default!)
-        where T : notnull
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => ensure.Value is not null
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is null."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static async Task<Ensure<T>> NotNull<T>(this Task<Ensure<T?>> ensureTask, Error error = default!)
-        where T : notnull
-    {
-        var ensure = await ensureTask.ConfigureAwait(false);
-        return ensure.State switch
-        {
-            ResultState.Success => ensure.Value is not null
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is null."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensureTask))
-        };
-    }
-
-    [Pure]
-    public static Ensure<T[]> NotEmpty<T>(this in Ensure<T[]> ensure, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => ensure.Value is not null && ensure.Value.Length > 0
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is empty."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static Ensure<List<T>> NotEmpty<T>(this in Ensure<List<T>> ensure, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => ensure.Value is not null && ensure.Value.Count > 0
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is empty."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static Ensure<IReadOnlyCollection<T>> NotEmpty<T>(this in Ensure<IReadOnlyCollection<T>> ensure, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => ensure.Value is not null && ensure.Value.Count > 0
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is empty."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static Ensure<ICollection<T>> NotEmpty<T>(this in Ensure<ICollection<T>> ensure, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => ensure.Value is not null && ensure.Value.Count > 0
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is empty."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static Ensure<IReadOnlyList<T>> NotEmpty<T>(this in Ensure<IReadOnlyList<T>> ensure, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => ensure.Value is not null && ensure.Value.Count > 0
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is empty."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static Ensure<IList<T>> NotEmpty<T>(this in Ensure<IList<T>> ensure, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => ensure.Value is not null && ensure.Value.Count > 0
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is empty."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static Ensure<IEnumerable<T>> NotEmpty<T>(this in Ensure<IEnumerable<T>> ensure, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => ensure.Value is not null && ensure.Value.Any()
-                ? new(ensure.Value, ensure.ValueExpression)
-                : new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is empty."), ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-    [Pure]
-    public static Ensure<string> NotEmpty(this in Ensure<string> ensure, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => string.IsNullOrEmpty(ensure.Value)
-                ? new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is empty."), ensure.ValueExpression)
-                : new(ensure.Value, ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
-
-    [Pure]
-    public static Ensure<string> NotWhitespace(this in Ensure<string> ensure, Error error = default!)
-    {
-        return ensure.State switch
-        {
-            ResultState.Success => string.IsNullOrWhiteSpace(ensure.Value)
-                ? new(error ?? Error.New(DefaultErrorType, $"Value {{{ensure.ValueExpression}}} is empty or consists exclusively of white-space characters."), ensure.ValueExpression)
-                : new(ensure.Value, ensure.ValueExpression),
-            ResultState.Error => new(ensure.Error!, ensure.ValueExpression),
-            _ => throw new EnsureNotInitializedException(nameof(ensure))
-        };
-    }
 }
 
 public readonly struct Ensure<T>
@@ -305,6 +25,7 @@ public readonly struct Ensure<T>
         Value = value;
         ValueExpression = valueExpression;
         State = ResultState.Success;
+        Error = default;
     }
 
     internal Ensure(Error error, string valueExpression)
@@ -314,10 +35,31 @@ public readonly struct Ensure<T>
         Value = default!;
         State = ResultState.Error;
     }
+
+    [Pure]
+    public static implicit operator Result<T>(in Ensure<T> ensure) => ensure.State switch
+    {
+        ResultState.Success => new(ensure.Value),
+        ResultState.Error => new(ensure.Error!),
+        _ => throw new EnsureNotInitializedException(nameof(ensure))
+    };
+
+    [Pure]
+    public static explicit operator Result(in Ensure<T> ensure) => ensure.State switch
+    {
+        ResultState.Success => new(null),
+        ResultState.Error => new(ensure.Error!),
+        _ => throw new EnsureNotInitializedException(nameof(ensure))
+    };
 }
 
 [Serializable]
-public class EnsureNotInitializedException(string variableName = "this") : InvalidOperationException("Ensure was not properly initialized.")
+public class EnsureNotInitializedException : InvalidOperationException
 {
-    public string VariableName { get; } = variableName;
+    public EnsureNotInitializedException(string variableName = "this")
+        : base("Ensure was not properly initialized.")
+    {
+        VariableName = variableName;
+    }
+    public string VariableName { get; }
 }

Railway/Error.cs

@@ -1,17 +1,12 @@
 using System.Collections;
-using System.Runtime.Serialization;
+using System.Collections.Immutable;
 using System.Text;
 
 namespace Just.Railway;
 
-[JsonPolymorphic(TypeDiscriminatorPropertyName = "$$err")]
+[JsonConverter(typeof(ErrorJsonConverter))]
-[JsonDerivedType(typeof(ExpectedError), typeDiscriminator: 0)]
-[JsonDerivedType(typeof(ExceptionalError), typeDiscriminator: 1)]
-[JsonDerivedType(typeof(ManyErrors))]
 public abstract class Error : IEquatable<Error>, IComparable<Error>
 {
-    private IDictionary<string, object>? _extensionData;
-
     protected internal Error(){}
 
     /// <summary>
@@ -34,16 +29,22 @@ public abstract class Error : IEquatable<Error>, IComparable<Error>
     /// </summary>
     /// <param name="message">Error detail</param>
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static Error New(string message) =>
+    public static Error New(string message, IEnumerable<KeyValuePair<string, string>>? extensionData = null) =>
-        new ExpectedError("error", message);
+        new ExpectedError("error", message)
+        {
+            ExtensionData = extensionData?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty
+        };
     /// <summary>
     /// Create an <see cref="ExpectedError"/>
     /// </summary>
     /// <param name="type">Error code</param>
     /// <param name="message">Error detail</param>
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static Error New(string type, string message) =>
+    public static Error New(string type, string message, IEnumerable<KeyValuePair<string, string>>? extensionData = null) =>
-        new ExpectedError(type, message);
+        new ExpectedError(type, message)
+        {
+            ExtensionData = extensionData?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty
+        };
     /// <summary>
     /// Create a <see cref="ManyErrors"/>
     /// </summary>
@@ -51,7 +52,7 @@ public abstract class Error : IEquatable<Error>, IComparable<Error>
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static Error Many(Error error1, Error error2) => (error1, error2) switch
     {
-        (null, null) => new ManyErrors(Enumerable.Empty<Error>()),
+        (null, null) => new ManyErrors(new List<Error>()),
         (Error err, null) => err,
         (Error err, { IsEmpty: true }) => err,
         (null, Error err) => err,
@@ -77,33 +78,14 @@ public abstract class Error : IEquatable<Error>, IComparable<Error>
 
     [Pure] public abstract string Type { get; }
     [Pure] public abstract string Message { get; }
-    [Pure, JsonExtensionData] public IDictionary<string, object> ExtensionData
-    {
-        get => _extensionData ??= new Dictionary<string, object>();
-        init => _extensionData = value ?? new Dictionary<string, object>();
-    }
-    [Pure] public object? this[string name]
-    {
-        get => _extensionData?.TryGetValue(name, out var val) == true ? val : null;
 
-        set
+    [Pure] public ImmutableDictionary<string, string> ExtensionData { get; internal init; } = ImmutableDictionary<string, string>.Empty;
-        {
+    [Pure] public string? this[string key] => ExtensionData.TryGetValue(key, out var value) == true ? value : null;
-            if (value is null)
-            {
-                _extensionData?.Remove(name);
-            }
-            else
-            {
-                _extensionData ??= new Dictionary<string, object>();
-                _extensionData[name] = value;
-            }
-        }
-    }
 
-    [Pure, JsonIgnore] public abstract int Count { get; }
+    [Pure] public abstract int Count { get; }
-    [Pure, JsonIgnore] public abstract bool IsEmpty { get; }
+    [Pure] public abstract bool IsEmpty { get; }
-    [Pure, JsonIgnore] public abstract bool IsExpected { get; }
+    [Pure] public abstract bool IsExpected { get; }
-    [Pure, JsonIgnore] public abstract bool IsExeptional { get; }
+    [Pure] public abstract bool IsExeptional { get; }
 
     [Pure] public Error Append(Error? next)
     {
@@ -163,9 +145,9 @@ public abstract class Error : IEquatable<Error>, IComparable<Error>
     }
 }
 
+[JsonConverter(typeof(ExpectedErrorJsonConverter))]
 public sealed class ExpectedError : Error
 {
-    [JsonConstructor]
     public ExpectedError(string type, string message)
     {
         Type = type;
@@ -179,10 +161,10 @@ public sealed class ExpectedError : Error
     [Pure] public override string Type { get; }
     [Pure] public override string Message { get; }
 
-    [Pure, JsonIgnore] public override int Count => 1;
+    [Pure] public override int Count => 1;
-    [Pure, JsonIgnore] public override bool IsEmpty => false;
+    [Pure] public override bool IsEmpty => false;
-    [Pure, JsonIgnore] public override bool IsExpected => true;
+    [Pure] public override bool IsExpected => true;
-    [Pure, JsonIgnore] public override bool IsExeptional => false;
+    [Pure] public override bool IsExeptional => false;
 
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
     public override IEnumerable<Error> ToEnumerable()
@@ -191,24 +173,27 @@ public sealed class ExpectedError : Error
     }
 }
 
+[JsonConverter(typeof(ExceptionalErrorJsonConverter))]
 public sealed class ExceptionalError : Error
 {
     internal readonly Exception? Exception;
 
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    internal static string ToErrorType(Type exceptionType) => exceptionType.FullName ?? exceptionType.Name;
+
     internal ExceptionalError(Exception exception)
-        : this(exception.GetType().Name, exception.Message)
+        : this(ToErrorType(exception.GetType()), exception.Message)
     {
         Exception = exception;
-        FillExtensionData(exception);
+        ExtensionData = ExtractExtensionData(exception);
     }
     internal ExceptionalError(string message, Exception exception)
-        : this(exception.GetType().Name, message)
+        : this(ToErrorType(exception.GetType()), message)
     {
         Exception = exception;
-        FillExtensionData(exception);
+        ExtensionData = ExtractExtensionData(exception);
     }
 
-    [JsonConstructor]
     public ExceptionalError(string type, string message)
     {
         Type = type;
@@ -218,10 +203,10 @@ public sealed class ExceptionalError : Error
     [Pure] public override string Type { get; }
     [Pure] public override string Message { get; }
 
-    [Pure, JsonIgnore] public override int Count => 1;
+    [Pure] public override int Count => 1;
-    [Pure, JsonIgnore] public override bool IsEmpty => false;
+    [Pure] public override bool IsEmpty => false;
-    [Pure, JsonIgnore] public override bool IsExpected => false;
+    [Pure] public override bool IsExpected => false;
-    [Pure, JsonIgnore] public override bool IsExeptional => true;
+    [Pure] public override bool IsExeptional => true;
 
     [Pure] public override Exception ToException() => Exception ?? base.ToException();
 
@@ -231,24 +216,38 @@ public sealed class ExceptionalError : Error
         yield return this;
     }
 
-    private void FillExtensionData(Exception exception)
+    private static ImmutableDictionary<string, string> ExtractExtensionData(Exception exception)
     {
+        if (!(exception.Data?.Count > 0))
+        return ImmutableDictionary<string, string>.Empty;
+
+        List<KeyValuePair<string, string>>? values = null;
+
         foreach (var key in exception.Data.Keys)
         {
+            if (key is null) continue;
+
             var value = exception.Data[key];
-            if (key is null || value is null)
+            if (value is null) continue;
-                continue;
+
-            this.ExtensionData[key.ToString() ?? string.Empty] = value;
+            var keyString = key.ToString();
+            var valueString = value.ToString();
+            if (string.IsNullOrEmpty(keyString) || string.IsNullOrEmpty(valueString)) continue;
+
+            values ??= new List<KeyValuePair<string, string>>(4);
+            values.Add(new(keyString, valueString));
         }
+        return values?.ToImmutableDictionary() ?? ImmutableDictionary<string, string>.Empty;
     }
 }
 
-[DataContract]
+[JsonConverter(typeof(ManyErrorsJsonConverter))]
-public sealed class ManyErrors : Error, IEnumerable<Error>
+public sealed class ManyErrors : Error, IEnumerable<Error>, IReadOnlyList<Error>
 {
     private readonly List<Error> _errors;
-    [Pure, DataMember] public IEnumerable<Error> Errors { get => _errors; }
+    [Pure] public IEnumerable<Error> Errors { get => _errors; }
 
+    internal ManyErrors(List<Error> errors) => _errors = errors;
     internal ManyErrors(Error head, Error tail)
     {
         _errors = new List<Error>(head.Count + tail.Count);
@@ -291,9 +290,11 @@ public sealed class ManyErrors : Error, IEnumerable<Error>
     }
 
     [Pure] public override int Count => _errors.Count;
-    [Pure, JsonIgnore] public override bool IsEmpty => _errors.Count == 0;
+    [Pure] public override bool IsEmpty => _errors.Count == 0;
-    [Pure, JsonIgnore] public override bool IsExpected => _errors.All(static x => x.IsExpected);
+    [Pure] public override bool IsExpected => _errors.All(static x => x.IsExpected);
-    [Pure, JsonIgnore] public override bool IsExeptional => _errors.Any(static x => x.IsExeptional);
+    [Pure] public override bool IsExeptional => _errors.Any(static x => x.IsExeptional);
+
+    [Pure] public Error this[int index] => _errors[index];
 
     [Pure] public override Exception ToException() => new AggregateException(_errors.Select(static x => x.ToException()));
     [Pure] public override IEnumerable<Error> ToEnumerable() => _errors;
@@ -379,7 +380,11 @@ public sealed class ManyErrors : Error, IEnumerable<Error>
 }
 
 [Serializable]
-public sealed class ErrorException(string type, string message) : Exception(message)
+public sealed class ErrorException : Exception
 {
-    public string Type { get; } = type ?? nameof(ErrorException);
+    public ErrorException(string type, string message) : base(message)
+    {
+        Type = type ?? nameof(ErrorException);
+    }
+    public string Type { get; }
 }

Railway/ErrorJsonConverter.cs

@@ -0,0 +1,182 @@
+using System.Collections.Immutable;
+
+namespace Just.Railway;
+
+public sealed class ErrorJsonConverter : JsonConverter<Error>
+{
+    public override Error? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        return reader.TokenType switch
+        {
+            JsonTokenType.StartObject => ToExpectedError(ReadOne(ref reader)),
+            JsonTokenType.StartArray => ReadMany(ref reader),
+            JsonTokenType.None => null,
+            JsonTokenType.Null => null,
+            _ => throw new JsonException("Unexpected JSON token.")
+        };
+    }
+
+    public override void Write(Utf8JsonWriter writer, Error value, JsonSerializerOptions options)
+    {
+        if (value is ManyErrors manyErrors)
+        {
+            writer.WriteStartArray();
+            foreach (var err in manyErrors)
+            {
+                WriteOne(writer, err);
+            }
+            writer.WriteEndArray();
+        }
+        else
+        {
+            WriteOne(writer, value);
+        }
+    }
+
+    internal static ManyErrors ReadMany(ref Utf8JsonReader reader)
+    {
+        List<Error> errors = new(4);
+        while (reader.Read())
+        {
+            if (reader.TokenType == JsonTokenType.StartObject)
+            {
+                errors.Add(ToExpectedError(ReadOne(ref reader)));
+            }
+        }
+        return new ManyErrors(errors);
+    }
+    internal static ExpectedError ToExpectedError(in (string Type, string Message, ImmutableDictionary<string, string> ExtensionData) errorInfo)
+        => new(errorInfo.Type, errorInfo.Message) { ExtensionData = errorInfo.ExtensionData };
+    internal static (string Type, string Message, ImmutableDictionary<string, string> ExtensionData) ReadOne(ref Utf8JsonReader reader)
+    {
+        ImmutableDictionary<string, string>.Builder? extensionData = null;
+        string type = "error";
+        string message = "";
+        while (reader.Read())
+        {
+            switch (reader.TokenType)
+            {
+                case JsonTokenType.PropertyName:
+                {
+                    var propname = reader.GetString();
+                    reader.Read();
+
+                    if (reader.TokenType == JsonTokenType.Null)
+                        break;
+
+                    while (reader.TokenType == JsonTokenType.Comment) reader.Read();
+
+                    if (!(reader.TokenType == JsonTokenType.String))
+                        throw new JsonException("Unable to deserialize Error type.");
+                    
+                    var propvalue = reader.GetString();
+                    if (string.IsNullOrEmpty(propvalue))
+                        break;
+
+                    if (propname == "type" || string.Equals(propname, "type", StringComparison.InvariantCultureIgnoreCase))
+                    {
+                        type = propvalue;
+                    }
+                    else if (propname == "msg" || string.Equals(propname, "msg", StringComparison.InvariantCultureIgnoreCase))
+                    {
+                        message = propvalue;
+                    }
+                    else if (!string.IsNullOrEmpty(propname))
+                    {
+                        extensionData ??= ImmutableDictionary.CreateBuilder<string, string>();
+                        extensionData.Add(propname, propvalue);
+                    }
+
+                    break;
+                }
+                case JsonTokenType.Comment: break;
+                case JsonTokenType.EndObject: goto endLoop;
+                default: throw new JsonException("Unable to deserialize Error type.");
+            }
+        }
+        endLoop:
+        return (type, message, extensionData?.ToImmutable() ?? ImmutableDictionary<string, string>.Empty);
+    }
+    internal static void WriteOne(Utf8JsonWriter writer, Error value)
+    {
+        writer.WriteStartObject();
+
+        writer.WriteString("type", value.Type);
+        writer.WriteString("msg", value.Message);
+
+        if (value.ExtensionData?.Count > 0)
+        {
+            foreach (var (key, val) in value.ExtensionData)
+            {
+                writer.WriteString(key, val);
+            }
+        }
+
+        writer.WriteEndObject();
+    }
+}
+
+public sealed class ExpectedErrorJsonConverter : JsonConverter<ExpectedError>
+{
+    public override ExpectedError? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        return reader.TokenType switch
+        {
+            JsonTokenType.StartObject => ErrorJsonConverter.ToExpectedError(ErrorJsonConverter.ReadOne(ref reader)),
+            JsonTokenType.None => null,
+            JsonTokenType.Null => null,
+            _ => throw new JsonException("Unexpected JSON token.")
+        };
+    }
+
+    public override void Write(Utf8JsonWriter writer, ExpectedError value, JsonSerializerOptions options)
+    {
+        ErrorJsonConverter.WriteOne(writer, value);
+    }
+}
+
+public sealed class ExceptionalErrorJsonConverter : JsonConverter<ExceptionalError>
+{
+    public override ExceptionalError? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        return reader.TokenType switch
+        {
+            JsonTokenType.StartObject => ToExceptionalError(ErrorJsonConverter.ReadOne(ref reader)),
+            JsonTokenType.None => null,
+            JsonTokenType.Null => null,
+            _ => throw new JsonException("Unexpected JSON token.")
+        };
+    }
+
+    public override void Write(Utf8JsonWriter writer, ExceptionalError value, JsonSerializerOptions options)
+    {
+        ErrorJsonConverter.WriteOne(writer, value);
+    }
+
+    private static ExceptionalError ToExceptionalError(in (string Type, string Message, ImmutableDictionary<string, string> ExtensionData) errorInfo)
+        => new(errorInfo.Type, errorInfo.Message) { ExtensionData = errorInfo.ExtensionData };
+}
+
+public sealed class ManyErrorsJsonConverter : JsonConverter<ManyErrors>
+{
+    public override ManyErrors? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        return reader.TokenType switch
+        {
+            JsonTokenType.StartArray => ErrorJsonConverter.ReadMany(ref reader),
+            JsonTokenType.None => null,
+            JsonTokenType.Null => null,
+            _ => throw new JsonException("Unexpected JSON token.")
+        };
+    }
+
+    public override void Write(Utf8JsonWriter writer, ManyErrors value, JsonSerializerOptions options)
+    {
+        writer.WriteStartArray();
+        foreach (var err in value)
+        {
+            ErrorJsonConverter.WriteOne(writer, err);
+        }
+        writer.WriteEndArray();
+    }
+}

Railway/Railway.csproj

@@ -1,14 +1,22 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
+    <LangVersion>10.0</LangVersion>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
-    <EmitCompilerGeneratedFiles Condition="'$(Configuration)'=='Debug'">true</EmitCompilerGeneratedFiles>
-
     <AssemblyName>Just.Railway</AssemblyName>
     <RootNamespace>Just.Railway</RootNamespace>
     
+    <Description>Base for railway-oriented programming in .NET. Package includes Result object, Error class and most of the common extensions.</Description>
+    <PackageTags>railway-oriented;functional;result-pattern;result-object;error-handling</PackageTags>
+    <Authors>JustFixMe</Authors>
+    <Copyright>Copyright (c) 2023-2024 JustFixMe</Copyright>
+    <PackageLicenseFile>LICENSE</PackageLicenseFile>
+    <PackageReadmeFile>README.md</PackageReadmeFile>
+    <RepositoryUrl>https://github.com/JustFixMe/Just.Railway/</RepositoryUrl>
+    
+    <EmitCompilerGeneratedFiles Condition="'$(Configuration)'=='Debug'">true</EmitCompilerGeneratedFiles>
     <ReleaseVersion Condition=" '$(ReleaseVersion)' == '' ">1.0.0</ReleaseVersion>
     <VersionSuffix Condition=" '$(VersionSuffix)' != '' ">$(VersionSuffix)</VersionSuffix>
     <VersionPrefix Condition=" '$(VersionSuffix)' != '' ">$(ReleaseVersion)</VersionPrefix>
@@ -20,6 +28,11 @@
     <InternalsVisibleTo Include="$(AssemblyName).Tests" />
   </ItemGroup>
 
+  <ItemGroup>
+    <None Include="..\README.md" Pack="true" PackagePath=""/>
+    <None Include="..\LICENSE" Pack="true" Visible="false" PackagePath=""/>
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\Railway.SourceGenerator\Railway.SourceGenerator.csproj"
                       OutputItemType="Analyzer"

Railway/ReflectionHelper.cs

@@ -1,5 +1,4 @@
 using System.Reflection;
-using System.Runtime.CompilerServices;
 
 namespace Just.Railway;
 
@@ -10,9 +9,8 @@ internal static class ReflectionHelper
 
     [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static int Compare<T>(T? left, T? right) => TypeReflectionCache<T>.CompareFunc(left, right);
-}
 
-file static class TypeReflectionCache<T>
+    private static class TypeReflectionCache<T>
     {
         public static readonly Func<T?, T?, bool> IsEqualFunc;
         public static readonly Func<T?, T?, int> CompareFunc;
@@ -65,3 +63,4 @@ file static class TypeReflectionCache<T>
             : right is null ? 1 : left.Value.CompareTo(right.Value);
     #pragma warning restore CS8604 // Possible null reference argument.
     }
+}

Railway/Result.cs

@@ -1,4 +1,3 @@
-
 namespace Just.Railway;
 
 internal enum ResultState : byte
@@ -8,6 +7,7 @@ internal enum ResultState : byte
 
 public readonly partial struct Result : IEquatable<Result>
 {
+    internal SuccessUnit Value => new();
     internal readonly Error? Error;
     internal readonly ResultState State;
 
@@ -17,22 +17,72 @@ public readonly partial struct Result : IEquatable<Result>
         State = error is null ? ResultState.Success : ResultState.Error;
     }
 
-    [Pure] public static Result Success() => new(null);
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
-    [Pure] public static Result<T> Success<T>(T value) => new(value);
+    public static Result Success() => new(null);
-    [Pure] public static Result Failure(Error error) => new(error ?? throw new ArgumentNullException(nameof(error)));
-    [Pure] public static Result<T> Failure<T>(Error error) => new(error ?? throw new ArgumentNullException(nameof(error)));
 
-    [Pure] public static implicit operator Result(Error error) => new(error ?? throw new ArgumentNullException(nameof(error)));
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
-    [Pure] public static implicit operator Result<SuccessUnit>(Result result) => result.State switch
+    public static Result<T> Success<T>(T value) => new(value);
+
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Result<(T1, T2)> Success<T1, T2>(T1 value1, T2 value2) => new((value1, value2));
+    
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Result<(T1, T2, T3)> Success<T1, T2, T3>(T1 value1, T2 value2, T3 value3) => new((value1, value2, value3));
+    
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Result<(T1, T2, T3, T4)> Success<T1, T2, T3, T4>(T1 value1, T2 value2, T3 value3, T4 value4) => new((value1, value2, value3, value4));
+    
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Result<(T1, T2, T3, T4, T5)> Success<T1, T2, T3, T4, T5>(T1 value1, T2 value2, T3 value3, T4 value4, T5 value5) => new((value1, value2, value3, value4, value5));
+
+
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Result Failure(Error error) => new(error ?? throw new ArgumentNullException(nameof(error)));
+
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Result Failure(Exception exception) => new(Error.New(exception) ?? throw new ArgumentNullException(nameof(exception)));
+
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Result<T> Failure<T>(Error error) => new(error ?? throw new ArgumentNullException(nameof(error)));
+
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Result<T> Failure<T>(Exception exception) => new(Error.New(exception) ?? throw new ArgumentNullException(nameof(exception)));
+
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator Result(Error error) => new(error ?? throw new ArgumentNullException(nameof(error)));
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator Result(Exception exception) => new(
+        new ExceptionalError(exception ?? throw new ArgumentNullException(nameof(exception))));
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator Result<SuccessUnit>(Result result) => result.State switch
     {
         ResultState.Success => new(new SuccessUnit()),
         ResultState.Error => new(result.Error!),
         _ => throw new ResultNotInitializedException(nameof(result))
     };
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static explicit operator Result(SuccessUnit _) => new(null);
 
     [Pure] public bool IsSuccess => Error is null;
     [Pure] public bool IsFailure => Error is not null;
 
+    [Pure] public bool Success([MaybeNullWhen(false)]out SuccessUnit? u, [MaybeNullWhen(true), NotNullWhen(false)]out Error? error)
+    {
+        switch (State)
+        {
+            case ResultState.Success:
+                u = new SuccessUnit();
+                error = default;
+                return true;
+
+            case ResultState.Error:
+                u = default;
+                error = Error!;
+                return false;
+
+            default: throw new ResultNotInitializedException();
+        }
+    }
     [Pure] public bool TryGetError([MaybeNullWhen(false)]out Error error)
     {
         if (IsSuccess)
@@ -91,20 +141,27 @@ public readonly struct Result<T> : IEquatable<Result<T>>
     {
         Value = value;
         State = ResultState.Success;
+        Error = default;
     }
 
-    [Pure] public static explicit operator Result(Result<T> result) => result.State switch
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static explicit operator Result(Result<T> result) => result.State switch
     {
         ResultState.Success => new(null),
         ResultState.Error => new(result.Error!),
         _ => throw new ResultNotInitializedException(nameof(result))
     };
-    [Pure] public static implicit operator Result<T>(Error error) => new(error);
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
-    [Pure] public static implicit operator Result<T>(T value) => new(value);
+    public static implicit operator Result<T>(Error error) => new(error);
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator Result<T>(Exception exception) => new(
+        new ExceptionalError(exception ?? throw new ArgumentNullException(nameof(exception))));
+    [Pure, MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator Result<T>(T value) => new(value);
     [Pure] public bool IsSuccess => State == ResultState.Success;
     [Pure] public bool IsFailure => State == ResultState.Error;
 
-    [Pure] public bool Unwrap([MaybeNullWhen(false)]out T value, [MaybeNullWhen(true)]out Error error)
+    [Pure] public bool Success([MaybeNullWhen(false)]out T value, [MaybeNullWhen(true), NotNullWhen(false)]out Error? error)
     {
         switch (State)
         {
@@ -218,7 +275,12 @@ public readonly struct SuccessUnit : IEquatable<SuccessUnit>
 }
 
 [Serializable]
-public class ResultNotInitializedException(string variableName = "this") : InvalidOperationException("Result was not properly initialized.")
+public class ResultNotInitializedException : InvalidOperationException
 {
-    public string VariableName { get; } = variableName;
+    public ResultNotInitializedException(string variableName = "this")
+        : base("Result was not properly initialized.")
+    {
+        VariableName = variableName;
+    }
+    public string VariableName { get; }
 }

Railway/ResultExtensions.cs

@@ -2,770 +2,115 @@ namespace Just.Railway;
 
 public static partial class ResultExtensions
 {
-    #region Match<>
+    #region Match (with fallback)
     
-    [Pure]
+    public static T Match<T>(this in Result<T> result, Func<Error, T> fallback)
-    public static R Match<R>(this in Result result, Func<R> onSuccess, Func<Error, R> onFailure)
     {
         return result.State switch
         {
-            ResultState.Success => onSuccess(),
+            ResultState.Success => result.Value,
-            ResultState.Error => onFailure(result.Error!),
+            ResultState.Error => fallback(result.Error!),
             _ => throw new ResultNotInitializedException(nameof(result))
         };
     }
     
-    [Pure]
+    public static async Task<T> Match<T>(this Result<T> result, Func<Error, Task<T>> fallback)
-    public static Task<R> Match<R>(this in Result result, Func<Task<R>> onSuccess, Func<Error, Task<R>> onFailure)
     {
         return result.State switch
         {
-            ResultState.Success => onSuccess(),
+            ResultState.Success => result.Value,
-            ResultState.Error => onFailure(result.Error!),
+            ResultState.Error => await fallback(result.Error!).ConfigureAwait(false),
             _ => throw new ResultNotInitializedException(nameof(result))
         };
     }
-
+    public static async Task<T> Match<T>(this Task<Result<T>> resultTask, Func<Error, T> fallback)
-    [Pure] public static async Task<R> Match<R>(this Task<Result> resultTask, Func<R> onSuccess, Func<Error, R> onFailure)
     {
         var result = await resultTask.ConfigureAwait(false);
         return result.State switch
         {
-            ResultState.Success => onSuccess(),
+            ResultState.Success => result.Value,
-            ResultState.Error => onFailure(result.Error!),
+            ResultState.Error => fallback(result.Error!),
             _ => throw new ResultNotInitializedException(nameof(resultTask))
         };
     }
-    [Pure]
+    public static async Task<T> Match<T>(this Task<Result<T>> resultTask, Func<Error, Task<T>> fallback)
-    public static async Task<R> Match<R>(this Task<Result> resultTask, Func<Task<R>> onSuccess, Func<Error, Task<R>> onFailure)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        var matchTask = result.State switch
-        {
-            ResultState.Success => onSuccess(),
-            ResultState.Error => onFailure(result.Error!),
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-        return await matchTask.ConfigureAwait(false);
-    }
-
-    #endregion
-
-    #region Map<>
-
-    [Pure]
-    public static Result<R> Map<R>(this in Result result, Func<R> mapping)
-    {
-        return result.State switch
-        {
-            ResultState.Success => mapping(),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-
-    [Pure]
-    public static async Task<Result<R>> Map<R>(this Result result, Func<Task<R>> mapping)
-    {
-        return result.State switch
-        {
-            ResultState.Success => await mapping().ConfigureAwait(false),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-
-    [Pure]
-    public static async Task<Result<R>> Map<R>(this Task<Result> resultTask, Func<R> mapping)
     {
         var result = await resultTask.ConfigureAwait(false);
         return result.State switch
         {
-            ResultState.Success => mapping(),
+            ResultState.Success => result.Value,
-            ResultState.Error => result.Error!,
+            ResultState.Error => await fallback(result.Error!).ConfigureAwait(false),
             _ => throw new ResultNotInitializedException(nameof(resultTask))
         };
     }
 
-    [Pure]
+    public static async ValueTask<T> Match<T>(this Result<T> result, Func<Error, ValueTask<T>> fallback)
-    public static async Task<Result<R>> Map<R>(this Task<Result> resultTask, Func<Task<R>> mapping)
+    {
+        return result.State switch
+        {
+            ResultState.Success => result.Value,
+            ResultState.Error => await fallback(result.Error!).ConfigureAwait(false),
+            _ => throw new ResultNotInitializedException(nameof(result))
+        };
+    }
+    public static async ValueTask<T> Match<T>(this ValueTask<Result<T>> resultTask, Func<Error, T> fallback)
     {
         var result = await resultTask.ConfigureAwait(false);
         return result.State switch
         {
-            ResultState.Success => await mapping().ConfigureAwait(false),
+            ResultState.Success => result.Value,
-            ResultState.Error => result.Error!,
+            ResultState.Error => fallback(result.Error!),
             _ => throw new ResultNotInitializedException(nameof(resultTask))
         };
     }
-
+    public static async ValueTask<T> Match<T>(this ValueTask<Result<T>> resultTask, Func<Error, ValueTask<T>> fallback)
-    #endregion
-
-    #region Bind<>
-
-    [Pure]
-    public static Result Bind(this in Result result, Func<Result> binding)
-    {
-        return result.State switch
-        {
-            ResultState.Success => binding(),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure]
-    public static Task<Result> Bind(this in Result result, Func<Task<Result>> binding)
-    {
-        return result.State switch
-        {
-            ResultState.Success => binding(),
-            ResultState.Error => Task.FromResult<Result>(result.Error!),
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure]
-    public static async Task<Result> Bind(this Task<Result> resultTask, Func<Result> binding)
     {
         var result = await resultTask.ConfigureAwait(false);
         return result.State switch
         {
-            ResultState.Success => binding(),
+            ResultState.Success => result.Value,
-            ResultState.Error => result.Error!,
+            ResultState.Error => await fallback(result.Error!).ConfigureAwait(false),
             _ => throw new ResultNotInitializedException(nameof(resultTask))
         };
     }
-    [Pure]
-    public static async Task<Result> Bind(this Task<Result> resultTask, Func<Task<Result>> binding)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        return result.State switch
-        {
-            ResultState.Success => await binding().ConfigureAwait(false),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-    }
-
-    [Pure]
-    public static Result<R> Bind<R>(this in Result result, Func<Result<R>> binding)
-    {
-        return result.State switch
-        {
-            ResultState.Success => binding(),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure]
-    public static Task<Result<R>> Bind<R>(this in Result result, Func<Task<Result<R>>> binding)
-    {
-        return result.State switch
-        {
-            ResultState.Success => binding(),
-            ResultState.Error => Task.FromResult<Result<R>>(result.Error!),
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure]
-    public static async Task<Result<R>> Bind<R>(this Task<Result> resultTask, Func<Result<R>> binding)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        return result.State switch
-        {
-            ResultState.Success => binding(),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-    }
-    [Pure]
-    public static async Task<Result<R>> Bind<R>(this Task<Result> resultTask, Func<Task<Result<R>>> binding)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        return result.State switch
-        {
-            ResultState.Success => await binding().ConfigureAwait(false),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-    }
-
-    #endregion
-
-    #region Append
-
-    #region <>
-
-    [Pure] public static Result Append(this in Result result, Result next)
-    {
-        Error? error = null;
-
-        if ((result.State & next.State) == ResultState.Bottom)
-        {
-            throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
-
-            static IEnumerable<string> GetBottom(ResultState r1, ResultState r2)
-            {
-                if (r1 == ResultState.Bottom)
-                    yield return nameof(result);
-                if (r2 == ResultState.Bottom)
-                    yield return nameof(next);
-            }
-        }
-        
-        if (result.IsFailure)
-        {
-            error += result.Error;
-        }
-        if (next.IsFailure)
-        {
-            error += next.Error;
-        }
-        return error is null
-            ? new(null)
-            : new(error);
-    }
-
-    #endregion
-
-    #region <T>
-
-    [Pure] public static Result<T> Append<T>(this in Result result, T value)
-    {
-        return result.State switch
-        {
-            ResultState.Success => value,
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure] public static Result<T> Append<T>(this in Result result, Result<T> next)
-    {
-        Error? error = null;
-
-        if ((result.State & next.State) == ResultState.Bottom)
-        {
-            throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
-
-            static IEnumerable<string> GetBottom(ResultState r1, ResultState r2)
-            {
-                if (r1 == ResultState.Bottom)
-                    yield return nameof(result);
-                if (r2 == ResultState.Bottom)
-                    yield return nameof(next);
-            }
-        }
-        
-        if (result.IsFailure)
-        {
-            error += result.Error;
-        }
-        if (next.IsFailure)
-        {
-            error += next.Error;
-        }
-        return error is null
-            ? new(next.Value)
-            : new(error);
-    }
-    [Pure] public static Result<T> Append<T>(this in Result<T> result, Result next)
-    {
-        Error? error = null;
-
-        if ((result.State & next.State) == ResultState.Bottom)
-        {
-            throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
-
-            static IEnumerable<string> GetBottom(ResultState r1, ResultState r2)
-            {
-                if (r1 == ResultState.Bottom)
-                    yield return nameof(result);
-                if (r2 == ResultState.Bottom)
-                    yield return nameof(next);
-            }
-        }
-        
-        if (result.IsFailure)
-        {
-            error += result.Error;
-        }
-        if (next.IsFailure)
-        {
-            error += next.Error;
-        }
-        return error is null
-            ? new(result.Value)
-            : new(error);
-    }
-    [Pure]
-    public static Result<T> Append<T>(this in Result result, Func<Result<T>> next)
-    {
-        return result.State switch
-        {
-            ResultState.Success => next(),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-
-    [Pure]
-    public static Task<Result<T>> Append<T>(this in Result result, Func<Task<Result<T>>> next)
-    {
-        return result.State switch
-        {
-            ResultState.Success => next(),
-            ResultState.Error => Task.FromResult<Result<T>>(result.Error!),
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure]
-    public static async Task<Result<T>> Append<T>(this Task<Result> resultTask, Func<Task<Result<T>>> next)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        return result.State switch
-        {
-            ResultState.Success => await next().ConfigureAwait(false),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-    }
-    [Pure]
-    public static async Task<Result<T>> Append<T>(this Task<Result> resultTask, Func<Result<T>> next)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        return result.State switch
-        {
-            ResultState.Success => next(),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-    }
-
-    #endregion
-
-    #region <T1, T2>
-
-    [Pure] public static Result<(T1, T2)> Append<T1, T2>(this in Result<T1> result, T2 value)
-    {
-        return result.State switch
-        {
-            ResultState.Success => (result.Value, value),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure] public static Result<(T1, T2)> Append<T1, T2>(this in Result<T1> result, Result<T2> next)
-    {
-        Error? error = null;
-
-        if ((result.State & next.State) == ResultState.Bottom)
-        {
-            throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
-
-            static IEnumerable<string> GetBottom(ResultState r1, ResultState r2)
-            {
-                if (r1 == ResultState.Bottom)
-                    yield return nameof(result);
-                if (r2 == ResultState.Bottom)
-                    yield return nameof(next);
-            }
-        }
-        
-        if (result.IsFailure)
-        {
-            error += result.Error;
-        }
-        if (next.IsFailure)
-        {
-            error += next.Error;
-        }
-        return error is null
-            ? new((result.Value, next.Value))
-            : new(error);
-    }
-    [Pure] public static Result<(T1, T2)> Append<T1, T2>(this in Result<(T1, T2)> result, Result next)
-    {
-        Error? error = null;
-
-        if ((result.State & next.State) == ResultState.Bottom)
-        {
-            throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
-
-            static IEnumerable<string> GetBottom(ResultState r1, ResultState r2)
-            {
-                if (r1 == ResultState.Bottom)
-                    yield return nameof(result);
-                if (r2 == ResultState.Bottom)
-                    yield return nameof(next);
-            }
-        }
-        
-        if (result.IsFailure)
-        {
-            error += result.Error;
-        }
-        if (next.IsFailure)
-        {
-            error += next.Error;
-        }
-        return error is null
-            ? new(result.Value)
-            : new(error);
-    }
-    [Pure]
-    public static Result<(T1, T2)> Append<T1, T2>(this in Result<T1> result, Func<Result<T2>> next)
-    {
-        return result.State switch
-        {
-            ResultState.Success => result.Append(next()),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure]
-    public static async Task<Result<(T1, T2)>> Append<T1, T2>(this Result<T1> result, Func<Task<Result<T2>>> next)
-    {
-        return result.State switch
-        {
-            ResultState.Success => result.Append(await next().ConfigureAwait(false)),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure]
-    public static async Task<Result<(T1, T2)>> Append<T1, T2>(this Task<Result<T1>> resultTask, Func<Task<Result<T2>>> next)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        return result.State switch
-        {
-            ResultState.Success => result.Append(await next().ConfigureAwait(false)),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-    }
-    [Pure]
-    public static async Task<Result<(T1, T2)>> Append<T1, T2>(this Task<Result<T1>> resultTask, Func<Result<T2>> next)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        return result.State switch
-        {
-            ResultState.Success => result.Append(next()),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-    }
-
-    #endregion
-
-    #region <T1, T2, T3>
-
-    [Pure] public static Result<(T1, T2, T3)> Append<T1, T2, T3>(this in Result<(T1, T2)> result, T3 value)
-    {
-        return result.State switch
-        {
-            ResultState.Success => (result.Value.Item1, result.Value.Item2, value),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure] public static Result<(T1, T2, T3)> Append<T1, T2, T3>(this in Result<(T1, T2)> result, Result<T3> next)
-    {
-        Error? error = null;
-
-        if ((result.State & next.State) == ResultState.Bottom)
-        {
-            throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
-
-            static IEnumerable<string> GetBottom(ResultState r1, ResultState r2)
-            {
-                if (r1 == ResultState.Bottom)
-                    yield return nameof(result);
-                if (r2 == ResultState.Bottom)
-                    yield return nameof(next);
-            }
-        }
-        
-        if (result.IsFailure)
-        {
-            error += result.Error;
-        }
-        if (next.IsFailure)
-        {
-            error += next.Error;
-        }
-        return error is null
-            ? new((result.Value.Item1, result.Value.Item2, next.Value))
-            : new(error);
-    }
-    [Pure] public static Result<(T1, T2, T3)> Append<T1, T2, T3>(this in Result<(T1, T2, T3)> result, Result next)
-    {
-        Error? error = null;
-
-        if ((result.State & next.State) == ResultState.Bottom)
-        {
-            throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
-
-            static IEnumerable<string> GetBottom(ResultState r1, ResultState r2)
-            {
-                if (r1 == ResultState.Bottom)
-                    yield return nameof(result);
-                if (r2 == ResultState.Bottom)
-                    yield return nameof(next);
-            }
-        }
-        
-        if (result.IsFailure)
-        {
-            error += result.Error;
-        }
-        if (next.IsFailure)
-        {
-            error += next.Error;
-        }
-        return error is null
-            ? new(result.Value)
-            : new(error);
-    }
-    [Pure]
-    public static Result<(T1, T2, T3)> Append<T1, T2, T3>(this in Result<(T1, T2)> result, Func<Result<T3>> next)
-    {
-        return result.State switch
-        {
-            ResultState.Success => result.Append(next()),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure]
-    public static async Task<Result<(T1, T2, T3)>> Append<T1, T2, T3>(this Result<(T1, T2)> result, Func<Task<Result<T3>>> next)
-    {
-        return result.State switch
-        {
-            ResultState.Success => result.Append(await next().ConfigureAwait(false)),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure]
-    public static async Task<Result<(T1, T2, T3)>> Append<T1, T2, T3>(this Task<Result<(T1, T2)>> resultTask, Func<Task<Result<T3>>> next)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        return result.State switch
-        {
-            ResultState.Success => result.Append(await next().ConfigureAwait(false)),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-    }
-    [Pure]
-    public static async Task<Result<(T1, T2, T3)>> Append<T1, T2, T3>(this Task<Result<(T1, T2)>> resultTask, Func<Result<T3>> next)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        return result.State switch
-        {
-            ResultState.Success => result.Append(next()),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-    }
-
-    #endregion
-
-    #region <T1, T2, T3, T4>
-
-    [Pure] public static Result<(T1, T2, T3, T4)> Append<T1, T2, T3, T4>(this in Result<(T1, T2, T3)> result, T4 value)
-    {
-        return result.State switch
-        {
-            ResultState.Success => (result.Value.Item1, result.Value.Item2, result.Value.Item3, value),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure] public static Result<(T1, T2, T3, T4)> Append<T1, T2, T3, T4>(this in Result<(T1, T2, T3)> result, Result<T4> next)
-    {
-        Error? error = null;
-
-        if ((result.State & next.State) == ResultState.Bottom)
-        {
-            throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
-
-            static IEnumerable<string> GetBottom(ResultState r1, ResultState r2)
-            {
-                if (r1 == ResultState.Bottom)
-                    yield return nameof(result);
-                if (r2 == ResultState.Bottom)
-                    yield return nameof(next);
-            }
-        }
-        
-        if (result.IsFailure)
-        {
-            error += result.Error;
-        }
-        if (next.IsFailure)
-        {
-            error += next.Error;
-        }
-        return error is null
-            ? new((result.Value.Item1, result.Value.Item2, result.Value.Item3, next.Value))
-            : new(error);
-    }
-    [Pure] public static Result<(T1, T2, T3, T4)> Append<T1, T2, T3, T4>(this in Result<(T1, T2, T3, T4)> result, Result next)
-    {
-        Error? error = null;
-
-        if ((result.State & next.State) == ResultState.Bottom)
-        {
-            throw new ResultNotInitializedException(string.Join(';', GetBottom(result.State, next.State)));
-
-            static IEnumerable<string> GetBottom(ResultState r1, ResultState r2)
-            {
-                if (r1 == ResultState.Bottom)
-                    yield return nameof(result);
-                if (r2 == ResultState.Bottom)
-                    yield return nameof(next);
-            }
-        }
-        
-        if (result.IsFailure)
-        {
-            error += result.Error;
-        }
-        if (next.IsFailure)
-        {
-            error += next.Error;
-        }
-        return error is null
-            ? new(result.Value)
-            : new(error);
-    }
-    [Pure]
-    public static Result<(T1, T2, T3, T4)> Append<T1, T2, T3, T4>(this in Result<(T1, T2, T3)> result, Func<Result<T4>> next)
-    {
-        return result.State switch
-        {
-            ResultState.Success => result.Append(next()),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure]
-    public static async Task<Result<(T1, T2, T3, T4)>> Append<T1, T2, T3, T4>(this Result<(T1, T2, T3)> result, Func<Task<Result<T4>>> next)
-    {
-        return result.State switch
-        {
-            ResultState.Success => result.Append(await next().ConfigureAwait(false)),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(result))
-        };
-    }
-    [Pure]
-    public static async Task<Result<(T1, T2, T3, T4)>> Append<T1, T2, T3, T4>(this Task<Result<(T1, T2, T3)>> resultTask, Func<Task<Result<T4>>> next)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        return result.State switch
-        {
-            ResultState.Success => result.Append(await next().ConfigureAwait(false)),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-    }
-    [Pure]
-    public static async Task<Result<(T1, T2, T3, T4)>> Append<T1, T2, T3, T4>(this Task<Result<(T1, T2, T3)>> resultTask, Func<Result<T4>> next)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        return result.State switch
-        {
-            ResultState.Success => result.Append(next()),
-            ResultState.Error => result.Error!,
-            _ => throw new ResultNotInitializedException(nameof(resultTask))
-        };
-    }
-
-    #endregion
-
-    #endregion
-
-    #region Tap<>
-    [Pure]
-    public static ref readonly Result Tap(this in Result result, Action? onSuccess = null, Action<Error>? onFailure = null)
-    {
-        switch (result.State)
-        {
-            case ResultState.Success:
-                onSuccess?.Invoke();
-                break;
-            case ResultState.Error:
-                onFailure?.Invoke(result.Error!);
-                break;
-
-            default: throw new ResultNotInitializedException(nameof(result));
-        }
-
-        return ref result;
-    }
-    [Pure]
-    public static async Task<Result> Tap(this Task<Result> resultTask, Action? onSuccess = null, Action<Error>? onFailure = null)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        switch (result.State)
-        {
-            case ResultState.Success:
-                onSuccess?.Invoke();
-                break;
-            case ResultState.Error:
-                onFailure?.Invoke(result.Error!);
-                break;
-
-            default: throw new ResultNotInitializedException(nameof(resultTask));
-        }
-
-        return result;
-    }
-    [Pure]
-    public static async Task<Result> Tap(this Result result, Func<Task>? onSuccess = null, Func<Error, Task>? onFailure = null)
-    {
-        switch (result.State)
-        {
-            case ResultState.Success:
-                if (onSuccess is not null)
-                    await onSuccess.Invoke().ConfigureAwait(false);
-                break;
-            case ResultState.Error:
-                if (onFailure is not null)
-                    await onFailure.Invoke(result.Error!).ConfigureAwait(false);
-                break;
-
-            default: throw new ResultNotInitializedException(nameof(result));
-        }
-
-        return result;
-    }
-    [Pure]
-    public static async Task<Result> Tap(this Task<Result> resultTask, Func<Task>? onSuccess = null, Func<Error, Task>? onFailure = null)
-    {
-        var result = await resultTask.ConfigureAwait(false);
-        switch (result.State)
-        {
-            case ResultState.Success:
-                if (onSuccess is not null)
-                    await onSuccess.Invoke().ConfigureAwait(false);
-                break;
-            case ResultState.Error:
-                if (onFailure is not null)
-                    await onFailure.Invoke(result.Error!).ConfigureAwait(false);
-                break;
-
-            default: throw new ResultNotInitializedException(nameof(resultTask));
-        }
-
-        return result;
-    }
 
     #endregion
     
     #region Merge
 
+    public static Result Merge(this IEnumerable<Result> results)
+    {
+        List<Error>? errors = null;
+        bool hasErrors = false;
+
+        foreach (var result in results.OrderBy(x => x.State))
+        {
+            switch (result.State)
+            {
+                case ResultState.Error:
+                    hasErrors = true;
+                    errors ??= new(4);
+                    errors.Add(result.Error!);
+                    break;
+
+                case ResultState.Success:
+                    if (hasErrors) goto afterLoop;
+                    break;
+                    
+                default: throw new ResultNotInitializedException(nameof(results));
+            }
+        }
+        afterLoop:
+        return hasErrors
+            ? new(new ManyErrors(errors!))
+            : new(null);
+    }
+    public static async Task<Result> Merge(this IEnumerable<Task<Result>> tasks)
+    {
+        var results = await Task.WhenAll(tasks).ConfigureAwait(false);
+        return results.Merge();
+    }
+
     public static Result<IEnumerable<T>> Merge<T>(this IEnumerable<Result<T>> results)
     {
         List<T>? values = null;
@@ -778,13 +123,13 @@ public static partial class ResultExtensions
             {
                 case ResultState.Error:
                     hasErrors = true;
-                    errors ??= [];
+                    errors ??= new(4);
                     errors.Add(result.Error!);
                     break;
 
                 case ResultState.Success:
                     if (hasErrors) goto afterLoop;
-                    values ??= [];
+                    values ??= new(4);
                     values.Add(result.Value);
                     break;
                     

Railway/Try.cs

@@ -0,0 +1,5 @@
+namespace Just.Railway;
+
+public static partial class Try
+{
+}

Raliway.Tests/EnsureExtensions/Satisfy.cs

@@ -7,6 +7,7 @@ public class Satisfy
     {
         var result = Ensure.That(69)
             .Satisfies(i => i < 100)
+            .LessThan(100)
             .Result();
 
         Assert.True(result.IsSuccess);
@@ -18,6 +19,7 @@ public class Satisfy
         var error = Error.New(Ensure.DefaultErrorType, "Value {69} does not satisfy the requirement.");
         var result = Ensure.That(69)
             .Satisfies(i => i > 100)
+            .GreaterThan(100)
             .Result();
 
         Assert.True(result.IsFailure);
@@ -32,6 +34,7 @@ public class Satisfy
             .NotEmpty()
             .NotWhitespace()
             .Satisfies(s => s == "69")
+            .EqualTo("69")
             .Result();
 
         Assert.True(result.IsSuccess);
@@ -47,6 +50,7 @@ public class Satisfy
             .NotEmpty()
             .NotWhitespace()
             .Satisfies(s => s == "69")
+            .EqualTo("69")
             .Result();
 
         Assert.True(result.IsFailure);

Raliway.Tests/Errors/Serialization.cs

@@ -6,40 +6,71 @@ public class Serialization
     public void WhenSerializingManyErrors()
     {
         // Given
-        Error many_errors = new ManyErrors(new Error[]{
+        Error many_errors = new ManyErrors(
-            new ExpectedError("err1", "msg1"){
+        [
-                ExtensionData = {
+            Error.New("err1", "msg1", new KeyValuePair<string, string>[]
-                    ["ext"] = "ext_value"
+            {
-                }
+                new("ext", "ext_value"),
-            },
+            }),
-            new ExceptionalError(new Exception("msg2")),
+            Error.New(new Exception("msg2")),
-        });
+        ]);
         // When
         var result = JsonSerializer.Serialize(many_errors);
         // Then
         Assert.Equal(
-            expected: "[{\"$$err\":0,\"Type\":\"err1\",\"Message\":\"msg1\",\"ext\":\"ext_value\"},{\"$$err\":1,\"Type\":\"Exception\",\"Message\":\"msg2\"}]",
+            expected: "[{\"type\":\"err1\",\"msg\":\"msg1\",\"ext\":\"ext_value\"},{\"type\":\"System.Exception\",\"msg\":\"msg2\"}]",
             result);
     }
 
     [Fact]
-    public void WhenDeserializingManyErrors()
+    public void WhenDeserializingManyErrorsAsError()
     {
         // Given
-        var json = "[{\"$$err\":0,\"Type\":\"err1\",\"Message\":\"msg1\",\"ext\":\"ext_value\"},{\"$$err\":1,\"Type\":\"Exception\",\"Message\":\"msg2\"}]";
+        var json = "[{\"type\":\"err1\",\"msg\":\"msg1\",\"ext1\":\"ext_value1\",\"ext2\":\"ext_value2\"},{\"type\":\"System.Exception\",\"msg\":\"msg2\"}]";
         // When
-        var result = JsonSerializer.Deserialize<Error[]>(json);
+        var result = JsonSerializer.Deserialize<Error>(json);
         // Then
-        Assert.True(result?.Length == 2);
+        Assert.IsType<ManyErrors>(result);
+        ManyErrors manyErrors = (ManyErrors)result;
+
+        Assert.True(manyErrors.Count == 2);
         Assert.Equal(
-            expected: new ManyErrors(new Error[]{
+            expected: Error.Many(
-                new ExpectedError("err1", "msg1"),
+                Error.New("err1", "msg1"),
-                new ExceptionalError(new Exception("msg2")),
+                Error.New(new Exception("msg2"))
-            }),
+            ).ToEnumerable(),
+            manyErrors
+        );
+        Assert.Equal(
+            expected: "ext_value1",
+            manyErrors[0]["ext1"]);
+        Assert.Equal(
+            expected: "ext_value2",
+            manyErrors[0]["ext2"]);
+    }
+
+    [Fact]
+    public void WhenDeserializingManyErrorsAsManyErrors()
+    {
+        // Given
+        var json = "[{\"type\":\"err1\",\"msg\":\"msg1\",\"ext1\":\"ext_value1\",\"ext2\":\"ext_value2\"},{\"type\":\"System.Exception\",\"msg\":\"msg2\"}]";
+        // When
+        var result = JsonSerializer.Deserialize<ManyErrors>(json);
+        // Then
+        Assert.NotNull(result);
+        Assert.True(result.Count == 2);
+        Assert.Equal(
+            expected: Error.Many(
+                Error.New("err1", "msg1"),
+                Error.New(new Exception("msg2"))
+            ).ToEnumerable(),
             result
         );
         Assert.Equal(
-            expected: "ext_value",
+            expected: "ext_value1",
-            result[0].ExtensionData["ext"].ToString());
+            result[0]["ext1"]);
+        Assert.Equal(
+            expected: "ext_value2",
+            result[0]["ext2"]);
     }
 }

Raliway.Tests/Results/Combine.cs

@@ -0,0 +1,78 @@
+namespace Raliway.Tests.Results;
+
+public class Combine
+{
+    [Fact]
+    public void TwoResultCombination_WhenThereIsAnError()
+    {
+        // Given
+        var result1 = Result.Success(1);
+        var result2 = Result.Failure(Error.New("some error"));
+        // When
+        var result = Result.Combine(result1, result2);
+        // Then
+        Assert.True(result.IsFailure);
+        Assert.Equal(result2.Error, result.Error);
+    }
+    [Fact]
+    public void TwoResultCombination_WhenThereAreTwoErrors()
+    {
+        // Given
+        var result1 = Result.Failure<byte>(Error.New("1"));
+        var result2 = Result.Failure(Error.New("2"));
+        // When
+        var result = Result.Combine(result1, result2);
+        // Then
+        Assert.True(result.IsFailure);
+        Assert.Equal(result1.Error + result2.Error, result.Error);
+    }
+    [Fact]
+    public void TwoResultCombination_WhenThereIsNoError()
+    {
+        // Given
+        var result1 = Result.Success(1);
+        var result2 = Result.Success(3.14);
+        // When
+        var result = Result.Combine(result1, result2);
+        // Then
+        Assert.True(result.IsSuccess);
+    }
+    [Fact]
+    public void ThreeResultCombination_WhenThereIsAnError()
+    {
+        // Given
+        var result1 = Result.Success(1);
+        var result2 = Result.Success(3.14);
+        var result3 = Result.Failure(Error.New("some error"));
+        // When
+        Result<(int, double)> result = Result.Combine(result1, result2, result3);
+        // Then
+        Assert.True(result.IsFailure);
+        Assert.Equal(result3.Error, result.Error);
+    }
+    [Fact]
+    public void ThreeResultCombination_WhenThereAreTwoErrors()
+    {
+        // Given
+        var result1 = Result.Failure<int?>(Error.New("1"));
+        var result2 = Result.Success(3.14);
+        var result3 = Result.Failure(Error.New("3"));
+        // When
+        Result<(int?, double)> result = Result.Combine(result1, result2, result3);
+        // Then
+        Assert.True(result.IsFailure);
+        Assert.Equal(result1.Error + result3.Error, result.Error);
+    }
+    [Fact]
+    public void ThreeResultCombination_WhenThereIsNoError()
+    {
+        // Given
+        var result1 = Result.Success(1);
+        var result2 = Result.Success(3.14);
+        var result3 = Result.Success();
+        // When
+        var result = Result.Combine(result1, result2, result3);
+        // Then
+        Assert.True(result.IsSuccess);
+    }
+}

Raliway.Tests/Results/GeneralUsage.cs

@@ -2,80 +2,6 @@ namespace Raliway.Tests.Results;
 
 public class GeneralUsage
 {
-    [Fact]
-    public void TwoResultCombination_WhenThereIsAnError()
-    {
-        // Given
-        var result1 = Result.Success(1);
-        var result2 = Result.Failure(Error.New("some error"));
-        // When
-        var result = Result.Combine(result1, result2);
-        // Then
-        Assert.True(result.IsFailure);
-        Assert.Equal(result2.Error, result.Error);
-    }
-    [Fact]
-    public void TwoResultCombination_WhenThereAreTwoErrors()
-    {
-        // Given
-        var result1 = Result.Failure<byte>(Error.New("1"));
-        var result2 = Result.Failure(Error.New("2"));
-        // When
-        var result = Result.Combine(result1, result2);
-        // Then
-        Assert.True(result.IsFailure);
-        Assert.Equal(result1.Error + result2.Error, result.Error);
-    }
-    [Fact]
-    public void TwoResultCombination_WhenThereIsNoError()
-    {
-        // Given
-        var result1 = Result.Success(1);
-        var result2 = Result.Success(3.14);
-        // When
-        var result = Result.Combine(result1, result2);
-        // Then
-        Assert.True(result.IsSuccess);
-    }
-    [Fact]
-    public void ThreeResultCombination_WhenThereIsAnError()
-    {
-        // Given
-        var result1 = Result.Success(1);
-        var result2 = Result.Success(3.14);
-        var result3 = Result.Failure(Error.New("some error"));
-        // When
-        Result<(int, double)> result = Result.Combine(result1, result2, result3);
-        // Then
-        Assert.True(result.IsFailure);
-        Assert.Equal(result3.Error, result.Error);
-    }
-    [Fact]
-    public void ThreeResultCombination_WhenThereAreTwoErrors()
-    {
-        // Given
-        var result1 = Result.Failure<int?>(Error.New("1"));
-        var result2 = Result.Success(3.14);
-        var result3 = Result.Failure(Error.New("3"));
-        // When
-        Result<(int?, double)> result = Result.Combine(result1, result2, result3);
-        // Then
-        Assert.True(result.IsFailure);
-        Assert.Equal(result1.Error + result3.Error, result.Error);
-    }
-    [Fact]
-    public void ThreeResultCombination_WhenThereIsNoError()
-    {
-        // Given
-        var result1 = Result.Success(1);
-        var result2 = Result.Success(3.14);
-        var result3 = Result.Success();
-        // When
-        var result = Result.Combine(result1, result2, result3);
-        // Then
-        Assert.True(result.IsSuccess);
-    }
-
     [Fact]
     public void ChainedResultExtensions_WhenThereIsNoError()
     {
@@ -104,10 +30,9 @@ public class GeneralUsage
     public void ChainedResultExtensions_WhenThereIsAnError()
     {
         // Given
-        
-        // When
         var error = Error.New("test");
         
+        // When
 
         var result = Result.Success()
             .Append(() => Result.Failure<int>(error))
@@ -115,7 +40,7 @@ public class GeneralUsage
             .Map((i, s) =>
             {
                 Assert.Fail();
-                return Result.Success("");
+                return "";
             })
             .Append("some")
             .Bind((s1, s2) => 
@@ -139,4 +64,109 @@ public class GeneralUsage
         // Then
         Assert.Equal("satisfied", result);
     }
+
+    [Fact]
+    public async Task ChainedResultAsyncExtensions_WhenThereIsNoError()
+    {
+        // Given
+
+        // When
+        var result = await Result.Success()
+            .Append(() => ValueTask.FromResult(Result.Success(1)))
+            .Append("test")
+            .Map((i, s) => $"{s}_{i}")
+            .Append("some")
+            .Bind(async (s1, s2) => await ValueTask.FromResult(Result.Success(string.Join(';', s1, s2))))
+            .Match(
+                onSuccess: s => s.ToUpper(),
+                onFailure: _ =>
+                {
+                    Assert.Fail();
+                    return "";
+                }
+            );
+        
+        Assert.Equal("TEST_1;SOME", result);
+    }
+
+    [Fact]
+    public async Task ChainedResultAsyncExtensions_WhenThereIsAnError()
+    {
+        // Given
+        var error = Error.New("test");
+        
+        // When
+
+        var result = await Result.Success()
+            .Append(() => Task.FromResult(Result.Failure<int>(error)))
+            .Append("test")
+            .Map((i, s) =>
+            {
+                Assert.Fail();
+                return "";
+            })
+            .Append("some")
+            .Bind(async (s1, s2) => 
+            {
+                Assert.Fail();
+                await Task.CompletedTask;
+                return Result.Success("");
+            })
+            .Match(
+                onSuccess: _ => 
+                {
+                    Assert.Fail();
+                    return "";
+                },
+                onFailure: err =>
+                {
+                    Assert.Equal(error, err);
+                    return "satisfied";
+                }
+            );
+
+        // Then
+        Assert.Equal("satisfied", result);
+    }
+
+    [Fact]
+    public void RecoverResultFromFailureState()
+    {
+        // Given
+        Result<string> failed = new NotImplementedException();
+        // When
+        var result = failed.TryRecover(err => 
+        {
+            Assert.IsType<NotImplementedException>(err.ToException());
+
+            if (err.Type == "System.NotImplementedException")
+                return "recovered";
+
+            Assert.Fail();
+            return "";
+        });
+        // Then
+        Assert.True(result.IsSuccess);
+        Assert.Equal("recovered", result.Value);
+    }
+
+    [Fact]
+    public void WhenCanNotRecoverResultFromFailureState()
+    {
+        // Given
+        var error = Error.New("test");
+        Result<string> failed = new NotImplementedException();
+        // When
+        var result = failed.TryRecover(err =>
+        {
+            if (err.Type == "System.NotImplementedException")
+                return error;
+            
+            Assert.Fail();
+            return "";
+        });
+        // Then
+        Assert.True(result.IsFailure);
+        Assert.Equal(error, result.Error);
+    }
 }