add failing test

Author: Rich-Harris

packages/kit/src/core/sync/write_types/test/slugs/_expected/$types.d.ts

@@ -12,7 +12,7 @@ type OutputDataShape<T> = MaybeWithVoid<
 		Record<string, any>
 >;
 type EnsureDefined<T> = T extends null | undefined ? {} : T;
-type LayoutParams = RouteParams & { rest?: string; slug?: string };
+type LayoutParams = RouteParams & { rest?: string; slug?: string; optional?: string | void };
 type LayoutParentData = EnsureDefined<{}>;
 
 export type LayoutServerData = null;

packages/kit/src/core/sync/write_types/test/slugs/_expected/x/[[optional]]/$types.d.ts

@@ -0,0 +1,14 @@
+import type * as Kit from '@sveltejs/kit';
+
+type Expand<T> = T extends infer O ? { [K in keyof O]: O[K] } : never;
+type RouteParams = { optional: string | void }
+type MaybeWithVoid<T> = {} extends T ? T | void : T;
+export type RequiredKeys<T> = { [K in keyof T]-?: {} extends { [P in K]: T[K] } ? never : K; }[keyof T];
+type OutputDataShape<T> = MaybeWithVoid<Omit<App.PageData, RequiredKeys<T>> & Partial<Pick<App.PageData, keyof T & keyof App.PageData>> & Record<string, any>>
+type EnsureDefined<T> = T extends null | undefined ? {} : T;
+type PageParentData = EnsureDefined<import('../../$types.js').LayoutData>;
+
+export type PageServerData = null;
+export type PageLoad<OutputData extends OutputDataShape<PageParentData> = OutputDataShape<PageParentData>> = Kit.Load<RouteParams, PageServerData, PageParentData, OutputData>;
+export type PageLoadEvent = Parameters<PageLoad>[0];
+export type PageData = Expand<Omit<PageParentData, keyof Kit.AwaitedProperties<Awaited<ReturnType<typeof import('../../../../../../x/[[optional]]/+page.js').load>>>> & EnsureDefined<Kit.AwaitedProperties<Awaited<ReturnType<typeof import('../../../../../../x/[[optional]]/+page.js').load>>>>>;

packages/kit/src/core/sync/write_types/test/slugs/x/[[optional]]/+page.js

@@ -0,0 +1,3 @@
+export function load() {
+	return { optional: 'optional' };
+}