10 replies

Type narrowing on `yield*` early-return

One thing I appreciate about

Effect.gen

Effect.gen

is "early return" by yielding an error. Eg.

const maybeValue = ...;
if (Option.isNone(maybeValue)) yield* new ErrorXYZ();
// this is not executed

const maybeValue = ...;
if (Option.isNone(maybeValue)) yield* new ErrorXYZ();
// this is not executed

This is great, specially coming from

fp-ts

fp-ts

where

Option.match

Option.match

forced the indentation of the main path under

onSome

onSome

.

I'm wondering about the best way to go about this. Specifically

maybeValue

maybeValue

above is not narrowed to

Option.Some<...>

Option.Some<...>

, its type is

Option.Option<...>

Option.Option<...>

. I've found a few alternatives but none I'm fully satisfied with.