🐛 Fix Either Apply implementation

src/utils/either.ts

@@ -1,5 +1,4 @@
 import type { Thunk, Unary } from '../types/common-types'
-import { isFunction } from './guards'
 
 type Nullable<T> = T | null | undefined
 
@@ -10,6 +9,7 @@ export interface IEitherStatic {
 	fromNullable: <TContext>(x: Nullable<TContext>) => IEither<NonNullable<TContext>, null>
 	right: <TContext, TLeftContext = TContext>(x: TContext) => IEither<TContext, TLeftContext>
 	left: <TContext, TRightContext = TContext>(x: TContext) => IEither<TRightContext, TContext>
+	of: <TContext, TLeftContext = TContext>(x: TContext) => IEither<TContext, TLeftContext>
 }
 
 export interface IEither<TRightContext, TLeftContext = TRightContext> {
@@ -30,15 +30,9 @@ export interface IEither<TRightContext, TLeftContext = TRightContext> {
 	leftChain: <TNewContext>(
 		onLeft: (ctx: TLeftContext) => IEither<TRightContext, TNewContext>,
 	) => IEither<TRightContext, TNewContext>
-	ap: <TNewContext>(
-		other: IEither<
-			TNewContext extends Unary<TRightContext>
-				? TNewContext
-				: TRightContext extends Unary<TNewContext>
-				? TNewContext
-				: never
-		>,
-	) => IEither<TNewContext, TLeftContext>
+	ap: <TNewRight, TNewLeft = TLeftContext>(
+		other: IEither<Unary<TRightContext, TNewRight>, Unary<TRightContext, TNewLeft>>,
+	) => IEither<TNewRight, TLeftContext>
 	swap: () => IEither<TLeftContext, TRightContext>
 	chain: <TNewContext, TFail>(
 		onRight: (ctx: TRightContext) => IEither<TNewContext, TFail>,
@@ -76,19 +70,7 @@ export const right = <TContext>(x: TContext): IEither<TContext> => ({
 	leftMap: () => right(x) as any,
 	leftChain: () => right(x) as any,
 	swap: () => left(x),
-	ap: (other) => {
-		const y: any = other.fold(
-			() => undefined,
-			(x) => x,
-		)
-		const isFunctionX = isFunction(x)
-
-		if (!isFunctionX && !isFunction(y)) {
-			throw new TypeError('At least one of the Eithers must hold a function to allow io.ap.')
-		}
-
-		return isFunctionX ? other.map(x as any) : right(y(x))
-	},
+	ap: (other) => (other.isRight ? (right(other[unsafeGet]()(x)) as any) : right(x)),
 	chain: (f) => f(x) as any,
 	fold: (_, onRight) => onRight(x),
 })
@@ -104,4 +86,5 @@ export const Either: IEitherStatic = {
 	fromNullable: (x) => (x == null ? left(null) : (right(x) as any)),
 	right: (x) => right(x) as any,
 	left: (x) => left(x),
+	of: (x) => right(x) as any,
 }