Stack overflow on certain platforms

[DanielRosenwasser]

From Hana Joo (@h-joo) at #45571

type SomeType = number | string | SomeType[];

declare var obj: { key: SomeType; };

declare namespace jasmine {
    interface Matchers<T> {
        toEqual(expected: Expected<T>): void;
    }

    type Expected<T> = T | {
        [K in keyof T]: ExpectedRecursive<T[K]>;
    }

    type ExpectedRecursive<T> = T | {
        [K in keyof T]: ExpectedRecursive<T[K]>;
    };
}

declare function expect<T>(actual: T): jasmine.Matchers<T>;

expect(obj).toEqual({ key: 'value1' });

With tsc or in the editor

> tsc -p src
src/index.ts:19:21 - error TS2589: Type instantiation is excessively deep and possibly infinite.

expect(obj).toEqual({key: 'value1'});
                    ~~~~~~~~~~~~~~~

Or in the playground for me:

simpleWorker.ts:125 Uncaught (in promise) RangeError: Maximum call stack size exceeded
    at isTypeAssignableTo (tsWorker.js:60285)
    at isApplicableIndexType (tsWorker.js:56207)
    at findApplicableIndexInfo (tsWorker.js:56187)
    at getApplicableIndexInfo (tsWorker.js:56236)
    at getPropertyTypeForIndexType (tsWorker.js:58675)
    at getIndexedAccessTypeOrUndefined (tsWorker.js:59018)
    at getIndexedAccessType (tsWorker.js:58940)
    at instantiateTypeWorker (tsWorker.js:60141)
    at instantiateTypeWithAlias (tsWorker.js:60092)
    at instantiateType (tsWorker.js:60075)

---

This seems to have been caused by the newly introduced recursive definition of
the IDBValidKey, and this causes an infinite type instantiation.

[DanielRosenwasser]

I managed to get a simpler repro by replacing IDBKey with

type SomeType = number | string | SomeType[];

[ahejlsberg]

Is the issue here the stack overflow in the playground? Best I can tell, the excessive depth error is expected behavior and also happens with versions prior to 4.4.

[ahejlsberg]

BTW, I'm not seeing the stack overflow in the playground.

[DanielRosenwasser]

Hm - there's a few things to note I think.

1. The "deep or possibly infinite" error is probably not desirable, but maybe the best we can do here, so I guess that's expected.
2. The fact that IDBValidKey changed was part of what triggered the investigation. The definition of IDBValidKey seems correct, so the fact that this type doesn't play well with Jasmine might be a pill we have to swallow for 4.4.
3. The stack overflow does seems like a problem. I see it in Edge, but not in Firefox or Node.

[ahejlsberg]

The stack overflow does seems like a problem. I see it in Edge, but not in Firefox or Node.

On nightly or 4.4.1-rc? We've increased the maximum instantiation depth from 50 to 500 in nightly, so that may have something to do with it.