Don't miscast when the spell can still be aborted (#4281).

This is a significant refactoring. All the spells now return a spret_type and
take a boolean which tells if the spell has actually failed.
Also some code clean up in _do_cast(). All spells have their own function now.

Also fix the following bugs:
* Properly abort fire storm if forced casting on a wall with '!'.
  Also put a message for forced out of range casting (like cloud spells).
* Casting summon elemental on an invisible monster aborted with no cost.
* if a summoning spell aborts because create_monster fails, you don't lose a
  turn. You still get a chance of miscast in this rare case.
* s2s, tukima and branding spells abort properly instead of consuming turn and
MP when player is not wielding appropriate object.
* s2s abort message when wielding a non-snakable.

1 files changed, 5 insertions, 3 deletions

diff --git a/crawl-ref/source/spl-tornado.cc b/crawl-ref/source/spl-tornado.cc
index f53d3142cb..f51b3a5e0e 100644
--- a/crawl-ref/source/spl-tornado.cc
+++ b/crawl-ref/source/spl-tornado.cc
@@ -107,7 +107,7 @@ static void _set_tornado_durations(int powc)
     you.attribute[ATTR_LEV_UNCANCELLABLE] = 1;
 }
 
-bool cast_tornado(int powc)
+spret_type cast_tornado(int powc, bool fail)
 {
     bool friendlies = false;
     for (radius_iterator ri(you.pos(), TORNADO_RADIUS, C_ROUND); ri; ++ri)
@@ -127,9 +127,11 @@ bool cast_tornado(int powc)
         && !yesno("There are friendlies around, are you sure you want to hurt them?",
                   true, 'n'))
     {
-        return false;
+        return SPRET_ABORT;
     }
 
+    fail_check();
+
     mprf("A great vortex of raging winds %s.",
          you.airborne() ? "appears around you"
                         : "appears and lifts you up");
@@ -141,7 +143,7 @@ bool cast_tornado(int powc)
     _set_tornado_durations(powc);
     burden_change();
 
-    return true;
+    return SPRET_SUCCESS;
 }
 
 static bool _mons_is_unmovable(const monster *mons)