Projectiles triggering linedefs

In various versions of Doom and Doom II, it is possible for a walk-over linedef to have its action activated by projectiles which cross the linedef.

Doom v1.3
In Doom v1.3 and lower, any projectile is capable of activating walk-over linedefs, as seen in the screenshots to the right where the player's plasma gun is being fired and the resulting projectiles have caused a nearby lift to lower. This was repaired by id Software starting with v1.4 via addition of the following code to the function in  at line 509 :

// Things that should NOT trigger specials... switch(thing->type) { 	 case MT_ROCKET: case MT_PLASMA: case MT_BFG: case MT_TROOPSHOT: case MT_HEADSHOT: case MT_BRUISERSHOT: return; break; default: break; }

Doom v1.666
Starting with the release of Doom II, various additional monsters were added which fire new projectile types, including the arachnotron, revenant, and mancubus. However, their corresponding projectile types were not added as cases in the switch statement added to originally repair the problem. This means that in v1.666 and all higher versions, walk-over linedef actions can again be activated by these projectiles.

It is notable that this problem could have been avoided by using a simple check, similar to one already present in the code for teleporters.