Fix bug involved infinite loop when player mon has only status moves (#…

…4403)

src/battle_ai_switch_items.c

@@ -1535,7 +1535,7 @@ static u32 GetSwitchinHitsToKO(s32 damageTaken, u32 battler)
     s32 currentHP = startingHP;
 
     // No damage being dealt
-    if (damageTaken + statusDamage + recurringDamage < recurringHealing)
+    if ((damageTaken + statusDamage + recurringDamage < recurringHealing) || damageTaken + statusDamage + recurringDamage == 0)
         return startingHP;
 
     // Mon fainted to hazards

test/battle/ai.c

@@ -545,6 +545,22 @@ AI_SINGLE_BATTLE_TEST("AI_FLAG_SMART_MON_CHOICES: Number of hits to KO calculati
     }
 }
 
+AI_SINGLE_BATTLE_TEST("AI_FLAG_SMART_MON_CHOICES: Number of hits to KO calculation checks whether incoming damage is zero to avoid an infinite loop")
+{
+    GIVEN {
+        AI_FLAGS(AI_FLAG_CHECK_BAD_MOVE | AI_FLAG_TRY_TO_FAINT | AI_FLAG_CHECK_VIABILITY | AI_FLAG_SMART_SWITCHING | AI_FLAG_SMART_MON_CHOICES);
+        PLAYER(SPECIES_BULBASAUR) { Level(5); Moves(MOVE_SWORDS_DANCE, MOVE_WHIRLWIND, MOVE_SAND_ATTACK, MOVE_TAIL_WHIP); }
+        // Scenario courtesy of Duke, who triggered the bug in the first place
+        OPPONENT(SPECIES_GEODUDE) { Level(100); Moves(MOVE_TACKLE); }
+        OPPONENT(SPECIES_GEODUDE) { Level(100); Moves(MOVE_TACKLE); }
+        OPPONENT(SPECIES_NOSEPASS) { Level(100); Moves(MOVE_TACKLE); }
+    } WHEN {
+            TURN { MOVE(player, MOVE_SWORDS_DANCE); EXPECT_MOVES(opponent, MOVE_TACKLE); }
+    } SCENE {
+        MESSAGE("Bulbasaur fainted!");
+    }
+}
+
 AI_SINGLE_BATTLE_TEST("AI_FLAG_SMART_MON_CHOICES: AI will not switch in a Pokemon which is slower and gets 1HKOed after fainting")
 {
     bool32 alakazamFirst;