Wrong error handling with Multiple Rest Parameters & Param Matchers in SvelteKit

This repository contains a minimal reproduction of a bug in SvelteKit related to error handling when using multiple rest parameters in route definitions.

Setup

Routes
[...prefix]/[event=eventSlug]/[id]/overview/+page.svelte
[...prefix]/[event=eventSlug]/[id]/details/+page.svelte
                                          ...
[...prefix]/[event=eventSlug]/[id]/[...rest]/+page.ts -> throw 404

[...prefix]/[event=eventSlug]/[id]/+error.svelte -> never called

Expected Behavior

When a request is made to a route that does not match any of the defined subpaths of /event/:id (e.g., /some/long/prefix/event|project/:id/invalid-path), the /event/:id/+error.svelte component should be rendered, displaying a 404 error page.

Actual Behavior

Instead of rendering the nested +error.svelte component, SvelteKit renders the top-most +error.svelte component, which is not what I would expect.

To be noted:

• The issue does not occur, when you remove the [...prefix] part of the route.
• It also does not occur, when you don't use a parameter in the route (e.g., event instead of [event=eventSlug]).