Do not redeclare TS lib

[james-pre]

After diving into worker-types with #1383, I realized that many of the workers-types are just modified from TS lib. Is there a reason for this? Why not extend pre-existing classes where needed?

For example, instead of re-declaring Body:

worker-types currently:

export declare abstract class Body {
  readonly body: ReadableStream | null;
  readonly bodyUsed: boolean;
  arrayBuffer(): Promise<ArrayBuffer>;
  text(): Promise<string>;
  json<T>(): Promise<T>;
  formData(): Promise<FormData>;
  blob(): Promise<Blob>;
}

lib.dom.d.ts (comments removed):

interface Body {
    readonly body: ReadableStream<Uint8Array> | null;
    readonly bodyUsed: boolean;
    arrayBuffer(): Promise<ArrayBuffer>;
    blob(): Promise<Blob>;
    formData(): Promise<FormData>;
    json(): Promise<any>;
    text(): Promise<string>;
}

Updated:
worker-types/alias.d.ts

export { Body };

worker-types/index.d.ts

import type { Body as FetchBody } from './alias';

export declare abstract class Body extends FetchBody {
  json<T>(): Promise<T>;
}

This would add a ton of reusability and compatibility to the types since the only code is changes from built-in classes. The following classes can use this approach:

• DOMException
• WorkerGlobalScope
• WorkerGlobalScopeEventMap
• Console
• console
• BufferSource
• WebAssembly
• ServiceWorkerGlobalScope
• addEventListener
• removeEventListener
• dispatchEvent
• btoa
• atob
• setTimeout
• clearTimeout
• setInterval
• queueMicrotask
• structuredClone
• fetch
• ...

I won't bother to list the 250+ symbols which only redeclare ones already present in TS lib, with little to no change.

[penalosa]

This is intentional. The types for @cloudflare/workers-types are generated directly from the workers runtime implementation, and so accurately match runtime behaviour. In most cases we're pretty close to spec-compliant with web standards, and so are similar to lib.dom.d.ts, but we recommend using @cloudflare/workers-types exclusively, and not typing your codebase against lib.dom.d.ts.