Typescript types do not work on undefined as first parameter

The following does not work:

          const myVar: { a: { b: string } } | null = null as {
            a: { b: string };
          } | null;
          const something = idx(myVar, _ => _.a.b);

[yungsters]

Thanks, @Horaddrim.

Sounds like this question has been resolved.

[macalinao]

@Horaddrim This doesn’t solve the problem for me.

    const myVar: { a: { b: string } } | null = null as {
      a: { b: string };
    } | null;
    const something = idx(myVar, _ => _.a.b) || "TEST";

still fails the build.

Please let me know if I failed any etiquette by opening a new issue. I’m not sure if I was supposed to do that-- sorry if I’m being annoying!