Don't move a trampler into tramplee's space until after the given attack.

This fixes crashes if either was moved off-level.  It does _not_ fix a
random monster with the same mindex continuing wuth the next attack on the
level you dropped to -- combat code is sprinkled with
attacked/defender->alive() which happily uses a stale pointer which, while
currently always pointing to an actor struct (you or menv[x]), may refer to
another monster which can happen to be alive and in range.

Also, for some reason attacker following doesn't obey traps.  This is more
fixable than it used to be, though.

1 files changed, 11 insertions, 0 deletions

diff --git a/crawl-ref/source/fineff.cc b/crawl-ref/source/fineff.cc
index 0ee75b3884..76f2f92c37 100644
--- a/crawl-ref/source/fineff.cc
+++ b/crawl-ref/source/fineff.cc
@@ -5,6 +5,7 @@
 **/
 
 #include "AppHdr.h"
+#include "coord.h"
 #include "effects.h"
 #include "env.h"
 #include "fineff.h"
@@ -101,6 +102,16 @@ void fire_final_effects()
                 attacker->hurt(defender, fe.x);
             }
             break;
+        case FINEFF_TRAMPLE_FOLLOW:
+            if (!attacker
+                || attacker->pos() == fe.pos
+                || !adjacent(attacker->pos(), fe.pos)
+                || !attacker->is_habitable(fe.pos))
+            {
+                continue;
+            }
+            attacker->move_to_pos(fe.pos);
+            break;
         }
     }
     env.final_effects.clear();