TypeScript error in config.ts: Conversion of type 'undefined' to type 'PromiseConstructorLike' may be a mistake

[kostrse]

RxJS: 6.5.3
TS: 3.6.2

src/internal/config.ts

export const config = {
  /**
   * The promise constructor used by default for methods such as
   * {@link toPromise} and {@link forEach}
   */
  Promise: undefined as PromiseConstructorLike,

Fails with compilation error:

TypeScript error in D:/Dev/OpDashBoard/FrontEnd/ClientApp/node_modules/rxjs/src/internal/config.ts(12,12):
Conversion of type 'undefined' to type 'PromiseConstructorLike' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first. TS2352

I think the fix would be to define it as:

  Promise: undefined as unknown as PromiseConstructorLike

Or maybe another, cleaner way.

Repro in Playground

[kostrse]

I got this error when accidentally imported a RxJS file under src/internal/ into my project

[cartant]

In the interim, you could - should, IMO - specify skipLibCheck in the compiler options in your tsconfig.json. There really is little point in having TypeScript check the internals of packages within node_modules when those packages contains .d.ts files that have already passed through the TypeScript compiler.

Ah, never mind - I just read your second comment.

[cartant]

I'm going to close this as it's a sub-case of a known issue: the TypeScript compiler options used to build RxJS are insufficiently strict. In particular, strictNullChecks is false. See #4968