Disallow newline after `as` after function instantiation

🔎 Search Terms

as newline ASI function type parameters spec difference

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

https://www.typescriptlang.org/play?#code/CYUwxgNghgTiAEAzArgOzAFwJYHtVJxwB4AVAPgAoBKALnhIChRJYFUoBbEAZwAcowCAGLwA3vBAAPXjhgZ4GAJ68EAcxAYMIGPAC88KKkXwAvk3DQ48CBoPc6hxQwY35kvQRzwi8AEzwyOwYhADp1TW0GIA

💻 Code

let x = foo < 2 > as
F.getter

🙁 Actual behavior

It is parsed as

let x = foo<2> as F.getter;

🙂 Expected behavior

It should be parsed as

let x = (foo < 2) > as;
F.getter;

Additional information about the issue

The linked code is valid JavaScript code, and it would be great if tsc could parse as such.

I know that TS is not in general a syntactic superset of JavaScript, but both Babel and SWC already parse this example (when in TS mode) according to JS semantics. We could change our parsers, but it would be better if this ambiguity could be solved in tsc.

cc @kdy1

Reproduce the parsing difference using the linked TypeScript Playground and the provided code sample, then trace how the TypeScript parser handles as across a newline after function instantiation. Done means the sample follows the expected JavaScript/ASI parse while existing TypeScript parsing behavior remains covered by tests.