Generate match method

Appegy.Union.Generator~/Appegy.Union.Generator/Union/Parts/UnionMatchPart.cs

@@ -0,0 +1,51 @@
+using System.CodeDom.Compiler;
+
+namespace Appegy.Union.Generator;
+
+public class UnionMatchPart : GeneratorPart<UnionAttributePartInput>
+{
+    public override void Generate(IndentedTextWriter codeWriter, UnionAttributePartInput input)
+    {
+        var types = input.Types;
+
+        codeWriter.WriteLine("public void Match(");
+
+        using (codeWriter.IndentScope())
+        {
+            for (var i = 0; i < types.Count; i++)
+            {
+                var type = types[i];
+                codeWriter.Write("global::System.Action<");
+                codeWriter.Write(type.FullName);
+                codeWriter.Write('>');
+                codeWriter.Write(' ');
+                codeWriter.Write(type.ParamName);
+                codeWriter.WriteLine(i != types.Count - 1 ? "," : ")");
+            }
+        }
+
+        codeWriter.WriteLine("{");
+        using (codeWriter.IndentScope())
+        {
+            codeWriter.WriteLine("switch (Type)");
+            codeWriter.WriteLine("{");
+            using (codeWriter.IndentScope())
+            {
+                foreach (var type in types)
+                {
+                    codeWriter.Write("case Kind.");
+                    codeWriter.Write(type.Name);
+                    codeWriter.Write(": ");
+                    codeWriter.Write(type.ParamName);
+                    codeWriter.Write("(");
+                    codeWriter.Write(type.FieldName);
+                    codeWriter.Write("); break;");
+                    codeWriter.WriteLine();
+                }
+                codeWriter.WriteLine("default: throw new global::System.InvalidOperationException($\"Unknown type of union: {_type}\");");
+            }
+            codeWriter.WriteLine("}");
+        }
+        codeWriter.WriteLine("}");
+    }
+}

Appegy.Union.Generator~/Appegy.Union.Generator/Union/UnionAttributeGenerator.cs

@@ -25,6 +25,7 @@ public class UnionAttributeGenerator : IIncrementalGenerator
                 new UnionFieldsPart(),
                 new UnionPropertiesPart(),
                 new UnionConstructorsPart(),
+                new UnionMatchPart(),
                 new UnionToStringPart(),
                 new UnionGetHashCodePart(),
                 new UnionEqualsPart(),

Appegy.Union.Generator~/Appegy.Union.Generator/Union/UnionAttributePartInput.cs

@@ -12,4 +12,5 @@ public readonly struct UnionTypeInfo(INamedTypeSymbol symbol)
     public readonly INamedTypeSymbol Symbol = symbol;
     public readonly string FullName = symbol.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat);
     public readonly string FieldName = symbol.GetFieldName();
+    public readonly string ParamName = symbol.GetParamName();
 }

Appegy.Union.Generator~/Appegy.Union.Generator/Utilities/CodeWriterExtensions.cs

@@ -1,4 +1,5 @@
-using System.CodeDom.Compiler;
+using System;
+using System.CodeDom.Compiler;
 using System.Collections.Generic;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
@@ -23,6 +24,11 @@ public static void AppendParts<T>(this IndentedTextWriter codeWriter, IReadOnlyL
         }
     }
 
+    public static IDisposable IndentScope(this IndentedTextWriter codeWriter)
+    {
+        return new  DisposableIndent(codeWriter);
+    }
+
     public static void WriteFieldName(this IndentedTextWriter codeWriter, ISymbol symbol)
     {
         var name = symbol.Name;

Appegy.Union.Generator~/Appegy.Union.Generator/Utilities/DisposableIndent.cs

@@ -0,0 +1,24 @@
+using System;
+using System.CodeDom.Compiler;
+
+namespace Appegy.Union.Generator;
+
+public struct DisposableIndent : IDisposable
+{
+    private readonly IndentedTextWriter _codeWriter;
+    private bool _isDisposed;
+
+    public DisposableIndent(IndentedTextWriter codeWriter)
+    {
+        _isDisposed = false;
+        _codeWriter = codeWriter;
+        _codeWriter.Indent++;
+    }
+
+    public void Dispose()
+    {
+        if (_isDisposed) return;
+        _codeWriter.Indent--;
+        _isDisposed = true;
+    }
+}

Appegy.Union.Generator~/Appegy.Union.Generator/Utilities/SyntaxTreeExtensions.cs

@@ -28,13 +28,23 @@ public static ImmutableList<INamedTypeSymbol> GetTypesFromConstructor(this Attri
     }
 
     public static string GetFieldName(this INamedTypeSymbol symbol)
+    {
+        var name = symbol.Name;
+        var param = symbol.GetParamName();
+
+        if (string.IsNullOrEmpty(param)) return string.Empty;
+
+        return "_" + param;
+    }
+
+    public static string GetParamName(this INamedTypeSymbol symbol)
     {
         var name = symbol.Name;
 
         if (string.IsNullOrEmpty(name)) return string.Empty;
 
         return name.Length > 1
-            ? "_" + char.ToLower(name[0]) + name.Substring(1)
-            : "_" + char.ToLower(name[0]);
+            ? char.ToLower(name[0]) + name.Substring(1)
+            : name.ToLower();
     }
 }