[Web API type definition issue] lib.dom options parameter for MutationObserver#observe should not be optional #2566

Summary

Not passing options, or passing options without minimum requirements, is an error (type error at runtime)

Expected vs. Actual Behavior

Expected:

Calling new MutationObserver(fn).observe(el) without a second options argument should show a type error because options are required.

Actual:

There is no type error. We discover the error at runtime.

Playground Link

https://www.typescriptlang.org/play/?#code/MYewdgzgLgBAtiGBeGYCmB3GBZArlAQygEtwB5AIwjQCcA3WgCkYEpkA+GAbwF8WAofgHohMAAJQIAWjQAPAA5pgUGTRogaMKAAs0MaqDA0AJjAI0A5rjhowsYhBg00AR1zFnpgsFAniYCy1ECEVgADoYADkQWHkCCAh-QOJYHXUMRwIYABUAT0UAUTUNfgQwkCpaBkZjEGBrWygwihBjXJYgA

Browser Support

• This API is supported in at least two major browser engines (not two Chromium-based browsers).

Have Tried The Latest Releases

• This issue applies to the latest release of TypeScript.
• This issue applies to the latest release of @types/web.

Additional Context

From MDN docs:

An object providing options that describe which DOM mutations should be reported to mutationObserver's callback. At a minimum, one of childList, attributes, and/or characterData must be true when you call observe(). Otherwise, a TypeError exception will be thrown.