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compiler/NubLang/Variant.cs

@@ -0,0 +1,75 @@
+using System.Diagnostics.CodeAnalysis;
+
+namespace NubLang;
+
+public readonly struct Variant<T1, T2> where T1 : notnull where T2 : notnull
+{
+    public Variant()
+    {
+        throw new InvalidOperationException("Variant must be initialized with a value");
+    }
+
+    public Variant(T1 value)
+    {
+        _value = value;
+    }
+
+    public Variant(T2 value)
+    {
+        _value = value;
+    }
+
+    private readonly object _value;
+
+    public void Match(Action<T1> on1, Action<T2> on2)
+    {
+        switch (_value)
+        {
+            case T1 v1:
+                on1(v1);
+                break;
+            case T2 v2:
+                on2(v2);
+                break;
+            default:
+                throw new InvalidCastException();
+        }
+    }
+
+    public T Match<T>(Func<T1, T> on1, Func<T2, T> on2)
+    {
+        return _value switch
+        {
+            T1 v1 => on1(v1),
+            T2 v2 => on2(v2),
+            _ => throw new InvalidCastException()
+        };
+    }
+
+    public bool IsCase1([NotNullWhen(true)] out T1? value)
+    {
+        if (_value is T1 converted)
+        {
+            value = converted;
+            return true;
+        }
+
+        value = default;
+        return false;
+    }
+
+    public bool IsCase2([NotNullWhen(true)] out T2? value)
+    {
+        if (_value is T2 converted)
+        {
+            value = converted;
+            return true;
+        }
+
+        value = default;
+        return false;
+    }
+
+    public static implicit operator Variant<T1, T2>(T1 value) => new(value);
+    public static implicit operator Variant<T1, T2>(T2 value) => new(value);
+}