Add ImmutableStack class

Collections/ImmutableStack.cs

@@ -0,0 +1,37 @@
+using System;
+
+namespace ModuleManager.Collections
+{
+    public class ImmutableStack<T>
+    {
+        public readonly T value;
+        public readonly ImmutableStack<T> parent;
+
+        public ImmutableStack(T value)
+        {
+            this.value = value;
+        }
+
+        private ImmutableStack(T value, ImmutableStack<T> parent)
+        {
+            this.value = value;
+            this.parent = parent;
+        }
+
+        public bool IsRoot => parent == null;
+        public ImmutableStack<T> Root => IsRoot? this : parent.Root;
+
+        public ImmutableStack<T> Push(T newValue)
+        {
+            return new ImmutableStack<T>(newValue, this);
+        }
+
+        public ImmutableStack<T> Pop()
+        {
+            if (IsRoot) throw new InvalidOperationException("Cannot pop from the root of a stack");
+            return parent;
+        }
+
+        public ImmutableStack<T> ReplaceValue(T newValue) => new ImmutableStack<T>(newValue, parent);
+    }
+}

ModuleManager.csproj

@@ -35,6 +35,7 @@
     <Compile Include="Cats\CatManager.cs" />
     <Compile Include="Cats\CatMover.cs" />
     <Compile Include="Cats\CatOrbiter.cs" />
+    <Compile Include="Collections\ImmutableStack.cs" />
     <Compile Include="MMPatchLoader.cs" />
     <Compile Include="ModuleManager.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />