fix(napi): type constraint for either types

examples/napi/__test__/typegen.spec.ts.md

@@ -57,6 +57,8 @@ Generated by [AVA](https://avajs.dev).
     export function either4(input: string | number | boolean | Obj): number␊
     export function receiveClassOrNumber(either: number | JsClassForEither): number␊
     export function receiveMutClassOrNumber(either: number | JsClassForEither): number␊
+    export function returnEitherClass(input: number): number | JsClassForEither␊
+    export function eitherFromOption(): JsClassForEither | undefined␊
     /** default enum values are continuos i32s start from 0 */␊
     export const enum Kind {␊
       /** Barks */␊

examples/napi/__test__/values.spec.ts

@@ -93,6 +93,8 @@ import {
   CssStyleSheet,
   asyncReduceBuffer,
   callbackReturnPromise,
+  returnEitherClass,
+  eitherFromOption,
 } from '../'
 
 test('export const', (t) => {
@@ -467,6 +469,15 @@ test('receive class reference in either', (t) => {
   t.is(receiveMutClassOrNumber(c), 100)
 })
 
+test('return either class', (t) => {
+  t.is(returnEitherClass(1), 1)
+  t.true(returnEitherClass(-1) instanceof JsClassForEither)
+})
+
+test('either from option', (t) => {
+  t.true(eitherFromOption() instanceof JsClassForEither)
+})
+
 test('either3', (t) => {
   t.is(either3(2), 2)
   t.is(either3('hello'), 'hello'.length)

examples/napi/index.d.ts

@@ -47,6 +47,8 @@ export interface Obj {
 export function either4(input: string | number | boolean | Obj): number
 export function receiveClassOrNumber(either: number | JsClassForEither): number
 export function receiveMutClassOrNumber(either: number | JsClassForEither): number
+export function returnEitherClass(input: number): number | JsClassForEither
+export function eitherFromOption(): JsClassForEither | undefined
 /** default enum values are continuos i32s start from 0 */
 export const enum Kind {
   /** Barks */

examples/napi/src/either.rs

@@ -82,3 +82,17 @@ fn receive_mut_class_or_number(either: Either<u32, &mut JsClassForEither>) -> u3
     Either::B(_) => 100,
   }
 }
+
+#[napi]
+fn return_either_class(input: i32) -> Either<u32, JsClassForEither> {
+  if input > 0 {
+    Either::A(input as u32)
+  } else {
+    Either::B(JsClassForEither {})
+  }
+}
+
+#[napi]
+fn either_from_option() -> Either<JsClassForEither, Undefined> {
+  Some(JsClassForEither {}).into()
+}