Fix bug [2874791], Merfolk stat change issues

Fix some conditions causing permanent stat loss or gain for Mf with
stat modifying boots.

Unmerge boots when the player starts levitating or flying on a water
square.

Use move_player_to_grid in blink, semi-controlled blink, and
teleportation.

Also fix a bug where Mf could random teleport into solid walls.

1 files changed, 9 insertions, 0 deletions

diff --git a/crawl-ref/source/it_use2.cc b/crawl-ref/source/it_use2.cc
index 84cdc0b4ed..5d3f4e795b 100644
--- a/crawl-ref/source/it_use2.cc
+++ b/crawl-ref/source/it_use2.cc
@@ -31,6 +31,8 @@ REVISION("$Rev$");
 #include "spl-mis.h"
 #include "spl-util.h"
 #include "stuff.h"
+#include "terrain.h"
+#include "transfor.h"
 #include "tutorial.h"
 #include "view.h"
 #include "xom.h"
@@ -243,6 +245,13 @@ bool potion_effect(potion_type pot_eff, int pow, bool drank_it, bool was_known)
             }
         }
 
+        // Merfolk boots unmeld if levitation takes us out of water
+        if(!player_is_airborne() && you.species == SP_MERFOLK
+           && grid_is_water(grd(you.pos())))
+        {
+            unmeld_one_equip(EQ_BOOTS);
+        }
+
         you.duration[DUR_LEVITATION] += 25 + random2(pow);
 
         if (you.duration[DUR_LEVITATION] > 100)