fix: fast list readonly mode not throwing exceptions

Engine.Core/Helpers/FastList.cs

@@ -8,13 +8,25 @@ public class FastList<T> : IList<T>, IReadOnlyList<T>, IEnumerable<T> where T :
     private readonly List<T> items = [];
     private readonly Dictionary<T, int> indexMap = [];
 
-    public int Count => items.Count;
-
     public bool IsReadOnly { get; set; } = false;
-    public T this[int index] { get => items[index]; set => items[index] = value; }
+    public int Count => items.Count;
+    public T this[int index]
+    {
+        get => items[index];
+        set
+        {
+            if (IsReadOnly)
+                throw new System.Data.ReadOnlyException();
+
+            items[index] = value;
+        }
+    }
 
     public void Add(T item)
     {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
         indexMap[item] = items.Count;
         items.Add(item);
     }
@@ -22,6 +34,9 @@ public class FastList<T> : IList<T>, IReadOnlyList<T>, IEnumerable<T> where T :
     public void RemoveAt(int i) => Remove(items[i], i);
     public bool Remove(T item)
     {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
         if (!indexMap.TryGetValue(item, out int index))
             return false;
 
@@ -44,6 +59,9 @@ public class FastList<T> : IList<T>, IReadOnlyList<T>, IEnumerable<T> where T :
 
     public void Insert(int index, T item)
     {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
         items.Insert(index, item);
 
         for (int i = index; i < items.Count; i++)
@@ -52,22 +70,28 @@ public class FastList<T> : IList<T>, IReadOnlyList<T>, IEnumerable<T> where T :
 
     public void Clear()
     {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
         items.Clear();
         indexMap.Clear();
     }
 
     public bool Contains(T item) => indexMap.ContainsKey(item);
-
+    public int IndexOf(T item) => items.IndexOf(item);
     public int BinarySearch(T item, IComparer<T>? comparer = null) => items.BinarySearch(item, comparer);
+
     public void Sort(IComparer<T> comparer)
     {
+        if (IsReadOnly)
+            throw new System.Data.ReadOnlyException();
+
         items.Sort(comparer);
 
         for (int i = 0; i < items.Count; i++)
             indexMap[items[i]] = i;
     }
 
-    public int IndexOf(T item) => items.IndexOf(item);
     public void CopyTo(T[] array, int arrayIndex) => items.CopyTo(array, arrayIndex);
 
     public IEnumerator<T> GetEnumerator() => items.GetEnumerator();