Gen 4: Fix Klutz not dropping Speed from Iron Ball (#562)

In Generation 4, if a Pokemon with the ability Klutz holds
an Iron Ball it should still get its Speed dropped. However, Klutz
Pokemon holding an Iron Ball won't be grounded.

Fixes #560

calc/src/mechanics/gen4.ts

@@ -144,8 +144,9 @@ export function calculateDPP(
 
   let typeEffectiveness = type1Effectiveness * type2Effectiveness;
 
-  // Iron Ball ignores Klutz in generation 4
-  if (typeEffectiveness === 0 && move.hasType('Ground') && defender.hasItem('Iron Ball')) {
+  // Klutz doesn't let Iron Ball ground in generation 4
+  if (typeEffectiveness === 0 && move.hasType('Ground') &&
+    (defender.hasItem('Iron Ball') && !defender.hasAbility('Klutz'))) {
     if (type1Effectiveness === 0) {
       type1Effectiveness = 1;
     } else if (defender.types[1] && type2Effectiveness === 0) {

calc/src/mechanics/util.ts

@@ -184,9 +184,11 @@ export function checkForecast(pokemon: Pokemon, weather?: Weather) {
 }
 
 export function checkItem(pokemon: Pokemon, magicRoomActive?: boolean) {
+  // Pokemon with Klutz still get their speed dropped in generation 4
+  if (pokemon.gen.num === 4 && pokemon.hasItem('Iron Ball')) return;
   if (
     pokemon.hasAbility('Klutz') && !EV_ITEMS.includes(pokemon.item!) ||
-      magicRoomActive
+    magicRoomActive
   ) {
     pokemon.item = '' as ItemName;
   }