From a16fbd3eaa165b3226a3b0ed9848b51718aaeafa Mon Sep 17 00:00:00 2001
From: Elizabeth <me@liz.coffee>
Date: Mon, 2 Jun 2025 18:55:32 -0700
Subject: Fixes when the map of an either is expected to be possible undefined

---
 u/fn/either.ts | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

(limited to 'u/fn/either.ts')

diff --git a/u/fn/either.ts b/u/fn/either.ts
index bf90f16..54f9fc2 100644
--- a/u/fn/either.ts
+++ b/u/fn/either.ts
@@ -32,14 +32,13 @@ export class Either<E, T> implements IEither<E, T> {
   private readonly self: Left<E> | Right<T>;
 
   private constructor(
-    err?: E,
-    ok?: T,
+    init: { err?: E, ok?: T },
     public readonly _tag: IEitherTag = iEitherTag,
   ) {
     this.self = <Left<E> | Right<T>>{
-      isLeft: typeof err !== "undefined",
-      isRight: typeof ok !== "undefined",
-      value: typeof err !== "undefined" ? err : ok!,
+      isLeft: "err" in init,
+      isRight: "ok" in init,
+      value: init.err ?? init.ok!,
     };
   }
 
@@ -86,10 +85,11 @@ export class Either<E, T> implements IEither<E, T> {
   }
 
   static left<E, T>(e: E): IEither<E, T> {
-    return new Either<E, T>(e, undefined);
+    return new Either<E, T>({ err: e});
   }
+
   static right<E, T>(t: T): IEither<E, T> {
-    return new Either<E, T>(undefined, t);
+    return new Either<E, T>({ok: t});
   }
 
   static fromFailable<E, T>(s: Supplier<T>): IEither<E, T> {
-- 
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