From 8852ebc0b3a8ee828c9f623493449c8a73cd9257 Mon Sep 17 00:00:00 2001
From: ike709 <ike709@github.com>
Date: Mon, 14 Oct 2024 21:26:30 -0500
Subject: [PATCH] Don't unnecessarily allocate lists for
 TreeEntry.InheritingTypes

---
 OpenDreamRuntime/Objects/DreamObjectTree.cs | 26 ++++++++++++---------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/OpenDreamRuntime/Objects/DreamObjectTree.cs b/OpenDreamRuntime/Objects/DreamObjectTree.cs
index 85d1f59f95..4d61d38e96 100644
--- a/OpenDreamRuntime/Objects/DreamObjectTree.cs
+++ b/OpenDreamRuntime/Objects/DreamObjectTree.cs
@@ -125,13 +125,15 @@ public bool TryGetGlobalProc(string name, [NotNullWhen(true)] out DreamProc? glo
     public IEnumerable<TreeEntry> GetAllDescendants(TreeEntry treeEntry) {
         yield return treeEntry;
 
-        foreach (int typeId in treeEntry.InheritingTypes) {
-            TreeEntry type = Types[typeId];
-            IEnumerator<TreeEntry> typeChildren = GetAllDescendants(type).GetEnumerator();
+        if (treeEntry.InheritingTypes is not null) {
+            foreach (int typeId in treeEntry.InheritingTypes) {
+                TreeEntry type = Types[typeId];
+                IEnumerator<TreeEntry> typeChildren = GetAllDescendants(type).GetEnumerator();
 
-            while (typeChildren.MoveNext()) yield return typeChildren.Current;
+                while (typeChildren.MoveNext()) yield return typeChildren.Current;
 
-            typeChildren.Dispose();
+                typeChildren.Dispose();
+            }
         }
     }
 
@@ -311,7 +313,7 @@ private void LoadTypesFromJson(DreamTypeJson[] types, ProcDefinitionJson[]? proc
 
             if (jsonType.Parent != null) {
                 TreeEntry parent = Types[jsonType.Parent.Value];
-
+                parent.InheritingTypes ??= new List<int>(1);
                 parent.InheritingTypes.Add(i);
                 type.ParentEntry = parent;
             }
@@ -488,11 +490,13 @@ public void SetNativeProc(TreeEntry type, Func<AsyncNativeProc.State, Task<Dream
     /// Enumerate the inheritance tree in post-order
     /// </summary>
     private IEnumerable<TreeEntry> TraversePostOrder(TreeEntry from) {
-        foreach (int typeId in from.InheritingTypes) {
-            TreeEntry type = Types[typeId];
-            using IEnumerator<TreeEntry> typeChildren = TraversePostOrder(type).GetEnumerator();
+        if (from.InheritingTypes is not null) {
+            foreach (int typeId in from.InheritingTypes) {
+                TreeEntry type = Types[typeId];
+                using IEnumerator<TreeEntry> typeChildren = TraversePostOrder(type).GetEnumerator();
 
-            while (typeChildren.MoveNext()) yield return typeChildren.Current;
+                while (typeChildren.MoveNext()) yield return typeChildren.Current;
+            }
         }
 
         yield return from;
@@ -505,7 +509,7 @@ public sealed class TreeEntry {
     public readonly int Id;
     public DreamObjectDefinition ObjectDefinition;
     public TreeEntry ParentEntry;
-    public readonly List<int> InheritingTypes = new();
+    public List<int>? InheritingTypes;
 
     /// <summary>
     /// This node's index in the inheritance tree based on a depth-first search<br/>