fix(types): union function prop (#3119)

fix #3357
2021-03-25 23:27:54 +08:00
parent 41e02f0fac
commit 3755e60c52
3 changed files with 53 additions and 7 deletions
--- a/test-dts/index.d.ts
+++ b/test-dts/index.d.ts
@@ -11,3 +11,9 @@ export function describe(_name: string, _fn: () => void): void
 export function expectType<T>(value: T): void
 export function expectError<T>(value: T): void
 export function expectAssignable<T, T2 extends T = T>(value: T2): void
+
+export type IsUnion<T, U extends T = T> = (T extends any
+  ? (U extends T ? false : true)
+  : never) extends false
+  ? false
+  : true