`resolve` allows non-existing routes (`$app/paths`)

[hyunbinseo]

Describe the bug

D:\_\SRC\ROUTES
│  +layout.svelte
│  +page.svelte
└─a
    └─b
        +page.svelte

resolve('/a') does not show a type error, even if the route does not exist:

<script>
  import { resolve } from '$app/paths';
</script>

<!-- No TypeScript error -->
<a href={resolve('/a')}>404</a>

/
/a - 404
/a/ - 404
/a/b
/a/b/

Reproduction

https://github.com/hyunbinseo/svelte-kit-14847

System Info

System:
  OS: Windows 11 10.0.26200
  CPU: (8) x64 Intel(R) Core(TM) Ultra 7 258V
  Memory: 5.50 GB / 31.48 GB
Binaries:
  Node: 24.11.0 - C:\Users\hyunb\AppData\Local\fnm_multishells\24128_1761755270547\node.EXE
  Yarn: 1.22.22 - C:\Users\hyunb\AppData\Local\fnm_multishells\24128_1761755270547\yarn.CMD
  npm: 11.6.1 - C:\Users\hyunb\AppData\Local\fnm_multishells\24128_1761755270547\npm.CMD
  pnpm: 10.20.0 - C:\Users\hyunb\AppData\Local\fnm_multishells\24128_1761755270547\pnpm.CMD
  Deno: 2.4.0 - C:\Users\hyunb\.deno\bin\deno.EXE
Browsers:
  Chrome: 141.0.7390.123
  Edge: Chromium (140.0.3485.54)
  Firefox: 144.0.2 - C:\Program Files\Mozilla Firefox\firefox.exe
npmPackages:
  @sveltejs/adapter-auto: ^6.1.0 => 6.1.1
  @sveltejs/kit: ^2.43.2 => 2.48.3
  @sveltejs/vite-plugin-svelte: ^6.2.0 => 6.2.1
  svelte: ^5.39.5 => 5.43.0
  vite: ^7.1.7 => 7.1.12

Severity

serious, but I can work around it

Additional Information

No response

[hyunbinseo]

When there are these two routes,

src\routes\+page.svelte
src\routes\a\[b]\c\+page.svelte

these do not trigger any TypeScript error:

<script>
  import { resolve } from '$app/paths';
</script>

<!-- href to non-existent route -->
<a href={resolve(`/a/${''}/c`)}>Link</a>

<!-- Causes runtime error, but no TypeScript error -->
<!-- Error: Missing parameter 'b' in route /a/[b] -->
<a href={resolve('/a/[b]', { b: '' })}>Link</a>
<a href={resolve('/a/[b]/c', { b: '' })}>Link</a>

[hyunbinseo]

Directories only having *.md files are suggested as a route ID as well:

resolve('/[type=type]/[date=date]/talk', {})

tree ./src/routes/[type=type]/[date=date]/talk /f

2025-07.md
2025-08.md
2025-09.md
2025-10.md
2025-11.md
2025-12.md