types: make event emitters use mapped event types (#7019)

typings/index.d.ts

@@ -609,6 +609,12 @@ export class ClientVoiceManager {
 
 export { Collection } from '@discordjs/collection';
 
+export interface CollectorEventTypes<K, V, F extends unknown[] = []> {
+  collect: [V, ...F];
+  dispose: [V, ...F];
+  end: [collected: Collection<K, V>, reason: string];
+}
+
 export abstract class Collector<K, V, F extends unknown[] = []> extends EventEmitter {
   protected constructor(client: Client, options?: CollectorOptions<[V, ...F]>);
   private _timeout: NodeJS.Timeout | null;
@@ -633,11 +639,15 @@ export abstract class Collector<K, V, F extends unknown[] = []> extends EventEmi
   public abstract collect(...args: unknown[]): K | null | Promise<K | null>;
   public abstract dispose(...args: unknown[]): K | null;
 
-  public on(event: 'collect' | 'dispose', listener: (...args: [V, ...F]) => Awaitable<void>): this;
-  public on(event: 'end', listener: (collected: Collection<K, V>, reason: string) => Awaitable<void>): this;
+  public on<EventKey extends keyof CollectorEventTypes<K, V, F>>(
+    event: EventKey,
+    listener: (...args: CollectorEventTypes<K, V, F>[EventKey]) => Awaitable<void>,
+  ): this;
 
-  public once(event: 'collect' | 'dispose', listener: (...args: [V, ...F]) => Awaitable<void>): this;
-  public once(event: 'end', listener: (collected: Collection<K, V>, reason: string) => Awaitable<void>): this;
+  public once<EventKey extends keyof CollectorEventTypes<K, V, F>>(
+    event: EventKey,
+    listener: (...args: CollectorEventTypes<K, V, F>[EventKey]) => Awaitable<void>,
+  ): this;
 }
 
 export interface ApplicationCommandInteractionOptionResolver<Cached extends CacheType = CacheType>
@@ -1829,6 +1839,16 @@ export class SelectMenuInteraction<Cached extends CacheType = CacheType> extends
   public inRawGuild(): this is SelectMenuInteraction<'raw'>;
 }
 
+export interface ShardEventTypes {
+  spawn: [child: ChildProcess];
+  death: [child: ChildProcess];
+  disconnect: [];
+  ready: [];
+  reconnection: [];
+  error: [error: Error];
+  message: [message: any];
+}
+
 export class Shard extends EventEmitter {
   private constructor(manager: ShardingManager, id: number);
   private _evals: Map<string, Promise<unknown>>;
@@ -1853,17 +1873,15 @@ export class Shard extends EventEmitter {
   public send(message: unknown): Promise<Shard>;
   public spawn(timeout?: number): Promise<ChildProcess>;
 
-  public on(event: 'spawn' | 'death', listener: (child: ChildProcess) => Awaitable<void>): this;
-  public on(event: 'disconnect' | 'ready' | 'reconnecting', listener: () => Awaitable<void>): this;
-  public on(event: 'error', listener: (error: Error) => Awaitable<void>): this;
-  public on(event: 'message', listener: (message: any) => Awaitable<void>): this;
-  public on(event: string, listener: (...args: any[]) => Awaitable<void>): this;
+  public on<K extends keyof ShardEventTypes>(
+    event: K,
+    listener: (...args: ShardEventTypes[K]) => Awaitable<void>,
+  ): this;
 
-  public once(event: 'spawn' | 'death', listener: (child: ChildProcess) => Awaitable<void>): this;
-  public once(event: 'disconnect' | 'ready' | 'reconnecting', listener: () => Awaitable<void>): this;
-  public once(event: 'error', listener: (error: Error) => Awaitable<void>): this;
-  public once(event: 'message', listener: (message: any) => Awaitable<void>): this;
-  public once(event: string, listener: (...args: any[]) => Awaitable<void>): this;
+  public once<K extends keyof ShardEventTypes>(
+    event: K,
+    listener: (...args: ShardEventTypes[K]) => Awaitable<void>,
+  ): this;
 }
 
 export class ShardClientUtil {
@@ -2352,6 +2370,14 @@ export class WebSocketManager extends EventEmitter {
   private triggerClientReady(): void;
 }
 
+export interface WebSocketShardEvents {
+  ready: [];
+  resumed: [];
+  invalidSession: [];
+  close: [event: CloseEvent];
+  allReady: [unavailableGuilds?: Set<Snowflake>];
+}
+
 export class WebSocketShard extends EventEmitter {
   private constructor(manager: WebSocketManager, id: number);
   private sequence: number;
@@ -2394,15 +2420,15 @@ export class WebSocketShard extends EventEmitter {
 
   public send(data: unknown, important?: boolean): void;
 
-  public on(event: 'ready' | 'resumed' | 'invalidSession', listener: () => Awaitable<void>): this;
-  public on(event: 'close', listener: (event: CloseEvent) => Awaitable<void>): this;
-  public on(event: 'allReady', listener: (unavailableGuilds?: Set<Snowflake>) => Awaitable<void>): this;
-  public on(event: string, listener: (...args: any[]) => Awaitable<void>): this;
+  public on<K extends keyof WebSocketShardEvents>(
+    event: K,
+    listener: (...args: WebSocketShardEvents[K]) => Awaitable<void>,
+  ): this;
 
-  public once(event: 'ready' | 'resumed' | 'invalidSession', listener: () => Awaitable<void>): this;
-  public once(event: 'close', listener: (event: CloseEvent) => Awaitable<void>): this;
-  public once(event: 'allReady', listener: (unavailableGuilds?: Set<Snowflake>) => Awaitable<void>): this;
-  public once(event: string, listener: (...args: any[]) => Awaitable<void>): this;
+  public once<K extends keyof WebSocketShardEvents>(
+    event: K,
+    listener: (...args: WebSocketShardEvents[K]) => Awaitable<void>,
+  ): this;
 }
 
 export class Widget extends Base {