limit depth of game_tick, just in case.

src/main/java/carpet/script/CarpetScriptServer.java

@@ -51,6 +51,7 @@ public class CarpetScriptServer
     public  Set<String> unloadableModules;
     public long tickStart;
     public boolean stopAll;
+    public int tickDepth;
     private  Set<String> holyMoly;
     public  CarpetEventServer events;
 

src/main/java/carpet/script/api/Auxiliary.java

@@ -634,8 +634,13 @@ public class Auxiliary {
 
 
         expression.addLazyFunction("game_tick", -1, (c, t, lv) -> {
-            ServerCommandSource s = ((CarpetContext)c).s;
+            CarpetContext cc = (CarpetContext)c;
+            ServerCommandSource s = cc.s;
             if (!s.getMinecraftServer().isOnThread()) throw new InternalExpressionException("Unable to run ticks from threads");
+            if (CarpetServer.scriptServer.tickDepth > 16) throw new InternalExpressionException("'game_tick' function caused other 'game_tick' functions to run. You should not allow that.");
+            try
+            {
+                CarpetServer.scriptServer.tickDepth ++;
                 ((MinecraftServerInterface) s.getMinecraftServer()).forceTick(() -> System.nanoTime() - CarpetServer.scriptServer.tickStart < 50000000L);
                 if (lv.size() > 0)
                 {
@@ -655,9 +660,14 @@ public class Auxiliary {
                 }
                 CarpetServer.scriptServer.tickStart = System.nanoTime(); // for the next tick
                 Thread.yield();
+            }
+            finally
+            {
+                CarpetServer.scriptServer.tickDepth --;
+            }
             if(CarpetServer.scriptServer.stopAll)
                 throw new ExitStatement(Value.NULL);
-            return (cc, tt) -> Value.TRUE;
+            return (_c, _t) -> Value.TRUE;
         });
 
         expression.addLazyFunction("seed", -1, (c, t, lv) -> {