re-thinking the result type

[harrysolovay]

The following boilerplate is starting to feel hefty.

if (result instanceof Error) {
  // ...
} else {
  // ...
}

While typing the result as a union avoids the need for a dedicated Result type, it complicates usage of the result. Perhaps the following would be better?

type Result<T, E extends Error> = {
  ok: T;
  error?: never;
} | {
  ok?: never;
  error: E;
}

This would allow for much simpler use of the ok value.

if (result.ok) {
  // ...
}

This would also enable the removal of intermediate nesting in cases such as entryRead, as we'd no longer need to worry about an any-typed ok resulting in the loss of error type narrowing.

Thoughts?