observable.map constructor type error in TS 5.9

[mbest]

Intended outcome:

Existing code continues to work.

Actual outcome:

Existing code generates a compiler error.

How to reproduce the issue:

Here is a working example in TypeScript 5.8

Here is the same code in TypeScript 5.9

The error is:

Argument of type '(string | Application)[][]' is not assignable to parameter of type 'IObservableMapInitialValues<string | Application, string | Application> | undefined'.
  Type '(string | Application)[][]' is not assignable to type 'IMapEntries<string | Application, string | Application>'.
    Type '(string | Application)[]' is not assignable to type 'IMapEntry<string | Application, string | Application>'.
      Target requires 2 element(s) but source may have fewer.(2345)

Versions

MobX 6.13.7
TypeScript 5.9.2

[mbest]

I found microsoft/TypeScript#62071, which mentions a workaround of adding as const. I'll do that for now, but maybe this can be fixed in MobX.

[mweststrate]

Confirmed, this predates tuple types but should be updated now.

[mbest]

I've submitted a PR with a fix.