- CostDiscard should only decrement Costs when the card that's in your hand can be used to pay the typing. (Fix Magmatic Insight)

forge-game/src/main/java/forge/game/cost/CostDiscard.java

@@ -137,8 +137,10 @@ public class CostDiscard extends CostPartWithList {
                 int adjustment = 0;
                 if (source.isInZone(ZoneType.Hand) && activator.equals(source.getOwner())) {
                     // If this card is in my hand, I can't use it to pay for it's own cost
+                    if (handList.contains(source)) {
                         adjustment = 1;
                     }
+                }
 
                 if ((amount != null) && (amount > handList.size() - adjustment)) {
                     // not enough cards in hand to pay