feat(question): add #33823 - OverloadedParameters

teamchong · teamchong · commit 0d6a10498855 · 2024-07-14T23:13:54.000Z
diff --git a/questions/33823-hard-overloadedparameters/README.md b/questions/33823-hard-overloadedparameters/README.md
@@ -0,0 +1,20 @@
+TypeScript’s `Parameters` don’t support overloaded functions, causing issues with type narrowing and undefined parameters during destructuring. The goal is to create utility types that extract parameters from all overloads, eliminating the need for `?.` and `!.` after type narrowing.
+
+```
+function func(fn: (arg: string) => string): string
+
+function func(num: number, init: Set<string>): boolean
+
+function func(...args: unknown[]): string | boolean {
+  const [fnOrNum, init] = args as OverloadedParameters<typeof func>
+
+  if (typeof fnOrNum === 'function') {
+    return fnOrNum("foo")
+  } else {
+    return fnOrNum === init.size
+  }
+}
+
+func((s) => `Hello ${s}`)
+func(1, new Set<string>('Hi'))
+```
diff --git a/questions/33823-hard-overloadedparameters/info.yml b/questions/33823-hard-overloadedparameters/info.yml
@@ -0,0 +1,6 @@
+difficulty: hard
+title: OverloadedParameters
+author:
+  github: teamchong
+  name: Steven
+
diff --git a/questions/33823-hard-overloadedparameters/template.ts b/questions/33823-hard-overloadedparameters/template.ts
@@ -0,0 +1 @@
+type OverloadedParameters = any
diff --git a/questions/33823-hard-overloadedparameters/test-cases.ts b/questions/33823-hard-overloadedparameters/test-cases.ts
@@ -0,0 +1,23 @@
+import type { Equal, Expect } from '@type-challenges/utils'
+import { ExpectFalse, NotEqual } from '@type-challenges/utils'
+
+function func(fn: (args: string) => string): string
+
+function func(num: number, init: Set<string>): boolean
+
+function func(...args: unknown[]): string | boolean {
+  const [fnOrNum, init] = args as OverloadedParameters<typeof func>
+
+  if (typeof fnOrNum === 'function') {
+    return fnOrNum("foo")
+  } else {
+    return fnOrNum === init.size
+  }
+}
+
+func((s) => `Hello ${s}`)
+func(1, new Set<string>('Hi'))
+
+type cases = [
+  Expect<Equal<OverloadedParameters<typeof func>, [number, Set<string>] | [(args: string) => string, never]>>,
+]
