computedFrom type guard when using filter

[tomer953]

Expected:
computedFrom operator should allow type narrowing
Small example using filterNil() to reproduce:

n = signal<number | undefined | null>(3);

  // filter with typeguard is working
  x$ = of(this.n()).pipe(
    filter((x): x is number => Boolean(x)),
    map((x) => (x as number) + 1)
  );
 
  // filterNil has typeguard already
  y$ = of(this.n()).pipe(
    filterNil(),
    map((x) => x + 1)
  );

  // but with computedFrom it failes to narrow
  z$ = computedFrom(
    [this.n],
    pipe(
      filterNil(),
      map(([x]) => x + 1) // x is possibly null or undefined
    )
  );

z$ should act like y$
I can’t find why this happens, @nartc might help here

Originally posted by @tomer953 in #73 (comment)

[tomalaforge]

`filterNil' only works for simple values, not array, and computedFrom is passing an array of element to your operator function

We would need a filterArrayNil or something similar

[tomer953]

oh i see. i thought the computedFrom flatten the array behind the scenes.
so actually its not broken. my bad