RangeError: Maximum call stack size exceeded at getAwaitedTypeNoAlias

[jakebailey]

Bug Report

Moved from #47208 (comment)

🔎 Search Terms

RangeError Maximum call stack size exceeded getAwaitedTypeNoAlias

🕗 Version & Regression Information

• This is the behavior in every version I tried.

⏯ Playground Link

Playground Link

💻 Code

type T = 1 | Promise<T> | T[];

export async function myFunction(param: T) {
  const awaited = await param
}

🙁 Actual behavior

     RangeError: Maximum call stack size exceeded
      at getAwaitedTypeNoAlias (src\compiler\checker.ts:36632:70)
      at mapper (src\compiler\checker.ts:36628:71)
      at mapType (src\compiler\checker.ts:23959:95)
      at getAwaitedTypeNoAlias (src\compiler\checker.ts:36629:60)
      at getAwaitedTypeNoAlias (src\compiler\checker.ts:36678:37)
      at mapper (src\compiler\checker.ts:36628:71)
      at mapType (src\compiler\checker.ts:23959:95)
      at getAwaitedTypeNoAlias (src\compiler\checker.ts:36629:60)
      at getAwaitedTypeNoAlias (src\compiler\checker.ts:36678:37)
      at mapper (src\compiler\checker.ts:36628:71)
      at mapType (src\compiler\checker.ts:23959:95)
      at getAwaitedTypeNoAlias (src\compiler\checker.ts:36629:60)
      at getAwaitedTypeNoAlias (src\compiler\checker.ts:36678:37)
      at mapper (src\compiler\checker.ts:36628:71)
      at mapType (src\compiler\checker.ts:23959:95)
      at getAwaitedTypeNoAlias (src\compiler\checker.ts:36629:60)
      at getAwaitedTypeNoAlias (src\compiler\checker.ts:36678:37)

🙂 Expected behavior

No crash.

[jakebailey]

Actually, this is a dupe of #49646 and should be fixed by #49677.

[fatcerberus]

type T = 1 | Promise<T> | T[];

I'm not sure how to read this type. Does this mean T is either:

• A 1
• An array of 1s
• An array of arrays of 1s
• A promise for a 1
• An array of promises for 1s
• A promise for an array of 1s
• A promise for an array of promises for 1s
• etc., inductively

...or is it just a completely circular definition?

[jakebailey]

It's just circular; there's an error message for types like these that can't be resolved (see the linked PR).

[fatcerberus]

That's what I thought; I guess I'm just confused because I thought when TS produced an error for a circular type it subsequently treated the type as any, which should be enough to prevent the crash on await... I guess the bug is that this case isn't being detected as circular

[Andarist]

I guess the bug is that this case isn't being detected as circular

Yep, notice how I've fixed this by just adding the circularity tracking~ here:
https://github.com/microsoft/TypeScript/pull/49677/files#diff-d9ab6589e714c71e657f601cf30ff51dfc607fc98419bf72e04f6b0fa92cc4b8R36628