feat: add 2857-hard-isrequiredkey

Author: coderhyy

type-challenges/2857-hard-isrequiredkey/template.ts

@@ -0,0 +1,18 @@
+// 1.
+// type IsRequiredKey<T, K extends keyof T = keyof T> = T extends {
+//   [P in K]-?: T[P];
+// }
+//   ? true
+//   : false;
+
+// 2.
+// type IsRequiredKey<T, K extends keyof T = keyof T> = T extends Required<
+//   Pick<T, K>
+// >
+//   ? true
+//   : false;
+
+// 3.
+type IsRequiredKey<T, K extends keyof T = keyof T> = T extends Record<K, T[K]>
+  ? true
+  : false;

type-challenges/2857-hard-isrequiredkey/test-cases.ts

@@ -0,0 +1,7 @@
+import type { Equal, Expect } from "@type-challenges/utils";
+
+type cases = [
+  Expect<Equal<IsRequiredKey<{ a: number; b?: string }, "a">, true>>,
+  Expect<Equal<IsRequiredKey<{ a: number; b?: string }, "b">, false>>,
+  Expect<Equal<IsRequiredKey<{ a: number; b?: string }, "b" | "a">, false>>
+];