fix(or): fixing typing for or

src/null-or.test.ts

@@ -0,0 +1,10 @@
+import * as $ from './index.js'
+
+test('simple', () => {
+ const union = $.or($.string, $.number)
+ const assert = $.nullOr(union)
+ expect(assert(null)).toEqual(null)
+ expect(assert(1)).toEqual(1)
+ expect(assert('foo')).toEqual('foo')
+ expect(() => assert(true)).toThrow('')
+})

src/or.test.ts

@@ -1,6 +1,7 @@
 import * as $ from './index.js'
 
 test('or', () => {
- const r = $.or($.number, $.string)(JSON.parse('"foo"'))
+ const assert = $.or($.number, $.string)
+ const r = assert(JSON.parse('"foo"'))
  expect(r).toEqual('foo')
 })

src/or.ts

@@ -1,12 +1,12 @@
-import type { Assert } from './prelude.js'
+import type { Assert, Asserted } from './prelude.js'
 import { inspect } from 'util'
 
-const or: <T extends Assert<unknown>[]>(...as: T) => T[number] =
- (...as) =>
- value => {
+const or =
+ <As extends Assert<unknown>[]>(...as: As) =>
+ (value: unknown) => {
  for (const a of as) {
  try {
- return a(value)
+ return a(value) as Asserted<As[number]>
  } catch (err) {
  continue
  }

src/prelude.ts

@@ -71,3 +71,6 @@ export type OptionalIfUndefinedOnly<T> = {
 
 export type OptionalIfUndefined<T> =
  Omit<T, keyof OptionalIfUndefinedOnly<T>> & OptionalIfUndefinedOnly<T>
+
+export type IntersectionOfUnion<T> =
+ (T extends unknown ? (_: T) => unknown : never) extends (_: infer R) => unknown ? R : never