fix(NavigationMenu): improve generic types (#2482)

Co-authored-by: Benjamin Canac <canacb1@gmail.com>

test/utils/types.ts

@@ -8,6 +8,19 @@ export function expectEmitPayloadType<T extends VNode, E extends keyof Events<T>
   return expectTypeOf<NonNullable<Events<T>[E]>>()
 }
 
-type Events<T> = T extends { __ctx?: { props: infer Props } } ? {
+/**
+ * Expect the type of a slot props.
+ */
+export function expectSlotProps<T extends VNode, S extends keyof Slots<T>>(_name: S, _cb: () => T) {
+  return expectTypeOf<Slots<T>[S]>()
+}
+
+type Ctx<V extends VNode> = V extends { __ctx?: infer C } ? NonNullable<C> : never
+
+type Slots<V extends VNode> = Ctx<V> extends { slots: infer S } ? {
+  [K in keyof S as S[K] extends never ? never : K]: S[K] extends (props: infer P) => any ? P : never
+} : never
+
+type Events<V extends VNode> = Ctx<V> extends { props: infer Props } ? {
   [K in keyof Props as K extends `on${infer E}${infer Rest}` ? `${Lowercase<E>}${Rest}` : never]: NonNullable<Props[K]> extends (...args: infer P) => any ? P : never
 } : never