From 30ca02afb597a23c9b9b00fec2612e16fedcbc5a Mon Sep 17 00:00:00 2001
From: Rohesie <rohesie@gmail.com>
Date: Wed, 25 Mar 2020 06:34:35 -0300
Subject: [PATCH] movespeed_modification unlawful list modification fix
 (#50135)

* copy

* Spooky suggestion
---
 code/__HELPERS/_lists.dm                      | 1 +
 code/modules/movespeed/_movespeed_modifier.dm | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/code/__HELPERS/_lists.dm b/code/__HELPERS/_lists.dm
index e90c3c15a2b..a448ca3d711 100644
--- a/code/__HELPERS/_lists.dm
+++ b/code/__HELPERS/_lists.dm
@@ -11,6 +11,7 @@
 
 #define LAZYINITLIST(L) if (!L) L = list()
 #define UNSETEMPTY(L) if (L && !length(L)) L = null
+#define LAZYCOPY(L) (L ? L.Copy() : list() )
 #define LAZYREMOVE(L, I) if(L) { L -= I; if(!length(L)) { L = null; } }
 #define LAZYADD(L, I) if(!L) { L = list(); } L += I;
 #define LAZYOR(L, I) if(!L) { L = list(); } L |= I;
diff --git a/code/modules/movespeed/_movespeed_modifier.dm b/code/modules/movespeed/_movespeed_modifier.dm
index 75fa6a706a6..0976f4d0671 100644
--- a/code/modules/movespeed/_movespeed_modifier.dm
+++ b/code/modules/movespeed/_movespeed_modifier.dm
@@ -199,7 +199,7 @@ GLOBAL_LIST_EMPTY(movespeed_modification_cache)
 
 /// Get the move speed modifiers list of the mob
 /mob/proc/get_movespeed_modifiers()
-	. = movespeed_modification
+	. = LAZYCOPY(movespeed_modification)
 	for(var/id in movespeed_mod_immunities)
 		. -= id