Placed spells are no longer lost when the player dies

src/main/java/com/minelittlepony/unicopia/ability/magic/Caster.java

@@ -73,6 +73,8 @@ public interface Caster<E extends LivingEntity> extends Owned<E>, Levelled, Affi
 
     /**
      * Removes the desired amount of mana or health from this caster in exchange for a spell's benefits.
+     * <p>
+     * @return False if the transaction has depleted the caster's reserves.
      */
     boolean subtractEnergyCost(double amount);
 

src/main/java/com/minelittlepony/unicopia/ability/magic/SpellPredicate.java

@@ -3,6 +3,7 @@ package com.minelittlepony.unicopia.ability.magic;
 import java.util.function.Predicate;
 
 import com.minelittlepony.unicopia.ability.magic.spell.AbstractDisguiseSpell;
+import com.minelittlepony.unicopia.ability.magic.spell.PlaceableSpell;
 import com.minelittlepony.unicopia.ability.magic.spell.ProjectileSpell;
 import com.minelittlepony.unicopia.ability.magic.spell.Spell;
 import com.minelittlepony.unicopia.ability.magic.spell.effect.ShieldSpell;
@@ -11,6 +12,7 @@ import net.minecraft.entity.Entity;
 
 public interface SpellPredicate<T extends Spell> extends Predicate<Spell> {
     SpellPredicate<IllusionarySpell> CAN_SUPPRESS = s -> s instanceof IllusionarySpell;
+    SpellPredicate<PlaceableSpell> IS_PLACED = s -> s instanceof PlaceableSpell;
     SpellPredicate<ProjectileSpell> HAS_PROJECTILE_EVENTS = s -> s instanceof ProjectileSpell;
     SpellPredicate<AbstractDisguiseSpell> IS_DISGUISE = s -> s instanceof AbstractDisguiseSpell;
     SpellPredicate<ShieldSpell> IS_SHIELD_LIKE = spell -> spell instanceof ShieldSpell;

src/main/java/com/minelittlepony/unicopia/ability/magic/spell/PlaceableSpell.java

@@ -85,7 +85,7 @@ public class PlaceableSpell extends AbstractDelegatingSpell {
                     CastSpellEntity entity = UEntities.CAST_SPELL.create(source.getWorld());
                     Vec3d pos = castEntity.getPosition().orElse(source.getOriginVector());
                     entity.updatePositionAndAngles(pos.x, pos.y, pos.z, 0, 0);
-                    entity.getSpellSlot().put(this);
+                    entity.getSpellSlot().put(spell.toPlaceable());
                     entity.setMaster(source);
                     entity.world.spawnEntity(entity);
 
@@ -107,8 +107,6 @@ public class PlaceableSpell extends AbstractDelegatingSpell {
             return super.tick(source, Situation.GROUND);
         }
 
-        this.onDestroyed(source);
-
         return !isDead();
     }
 

src/main/java/com/minelittlepony/unicopia/entity/CastSpellEntity.java

@@ -104,7 +104,13 @@ public class CastSpellEntity extends LightEmittingEntity implements Caster<Livin
 
     @Override
     public boolean subtractEnergyCost(double amount) {
-        return Caster.of(getMaster()).filter(c -> c.subtractEnergyCost(amount)).isPresent();
+        if (getMaster() == null) {
+            return true;
+        }
+
+        return Caster.of(getMaster())
+                .filter(c -> c.subtractEnergyCost(amount))
+                .isPresent();
     }
 
     @Override

src/main/java/com/minelittlepony/unicopia/entity/EntityReference.java

@@ -9,6 +9,7 @@ import org.jetbrains.annotations.Nullable;
 import com.minelittlepony.unicopia.util.NbtSerialisable;
 
 import net.minecraft.entity.Entity;
+import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.nbt.NbtCompound;
 import net.minecraft.nbt.NbtElement;
 import net.minecraft.server.world.ServerWorld;
@@ -89,7 +90,7 @@ public class EntityReference<T extends Entity> implements NbtSerialisable {
 
     private boolean checkReference(Entity e) {
         pos = Optional.of(e.getPos());
-        return !e.isRemoved();
+        return e instanceof PlayerEntity || !e.isRemoved();
     }
 
     @Override

src/main/java/com/minelittlepony/unicopia/entity/player/Pony.java

@@ -508,7 +508,9 @@ public class Pony extends Living<PlayerEntity> implements Transmittable, Copieab
     public void copyFrom(Pony oldPlayer) {
         speciesPersisted = oldPlayer.speciesPersisted;
         if (!oldPlayer.getEntity().isRemoved()) {
-            getSpellSlot().put(oldPlayer.getSpellSlot().get(true).orElse(null));
+            oldPlayer.getSpellSlot().stream(true).forEach(getSpellSlot()::put);
+        } else {
+            oldPlayer.getSpellSlot().stream(true).filter(SpellPredicate.IS_PLACED).forEach(getSpellSlot()::put);
         }
         oldPlayer.getSpellSlot().put(null);
         setSpecies(oldPlayer.getSpecies());

src/main/java/com/minelittlepony/unicopia/network/datasync/NetworkedReferenceSet.java

@@ -48,6 +48,9 @@ public class NetworkedReferenceSet<T> {
     public boolean clear() {
         dirty |= !ids.isEmpty() || !values.isEmpty();
         ids.clear();
+        for (NetworkedReference<T> reference : values.values()) {
+            reference.updateReference(null);
+        }
         values.clear();
         return dirty;
     }