Revert "Revert predicate stuff for now"

This reverts commit 565e18fcb2.

src/battle-scene.ts

@@ -19,7 +19,12 @@ import {
   type Constructor,
 } from "#app/utils/common";
 import { deepMergeSpriteData } from "#app/utils/data";
-import type { Modifier, ModifierPredicate, TurnHeldItemTransferModifier } from "./modifier/modifier";
+import type {
+  Modifier,
+  ModifierIdentityPredicate,
+  ModifierPredicate,
+  TurnHeldItemTransferModifier,
+} from "./modifier/modifier";
 import {
   ConsumableModifier,
   ConsumablePokemonModifier,
@@ -3361,6 +3366,11 @@ export default class BattleScene extends SceneBase {
     return (isPlayer ? this.modifiers : this.enemyModifiers).filter(modifierFilter);
   }
 
+  findModifier<T extends PersistentModifier>(
+    modifierFilter: ModifierIdentityPredicate<T>,
+    player?: boolean,
+  ): T | undefined;
+  findModifier(modifierFilter: ModifierPredicate, player?: boolean): PersistentModifier | undefined;
   /**
    * Find the first modifier that pass the `modifierFilter` function
    * @param modifierFilter The function used to filter a target's modifiers

src/modifier/modifier.ts

@@ -55,6 +55,7 @@ import {
 import { globalScene } from "#app/global-scene";
 
 export type ModifierPredicate = (modifier: Modifier) => boolean;
+export type ModifierIdentityPredicate<T extends Modifier> = (modifier: Modifier) => modifier is T;
 
 const iconOverflowIndex = 24;