When omitting $types, the type assigned to page load differs from PageLoad

Reproduce the mismatch using src/app.d.ts and src/routes/+page.ts, then run npm run check with and without the PageLoad annotation. Compare the inferred return type with the explicit PageLoad behavior; done means both forms consistently report the missing required PageData property or otherwise follow the documented typing contract.

Describe the bug

When omitting $types from +page.ts, the return type of the load doesn't seem to be checked correctly. When typed as PageLoad, required properties in PageData which aren't present in the return type cause a type error. If the types are omitted (as described in the blog post), the type error no longer occurs.

Reproduction

1. Run npm create svelte@latest repro && cd repro && npm install (select "Skeleton project", "Yes, using TypeScript syntax", and no additions).

2. Run npm run check — no errors or warnings, yet.

3. Edit src/app.d.ts; uncomment PageData and give it the properties { foo: string; bar: string; }.

4. Create src/routes/+page.ts with the contents:

   import type { PageLoad } from './$types';
   
   export const load: PageLoad = () => {
     return { foo: "exists" };
   };
   

5. Run npm run check again — this time, there's a type error saying that "Property 'bar' is missing …" (shown in full in the "Logs" section).

6. Edit src/routes/+page.ts, removing the import and type annotation.

7. Run npm run check one more time — the type error is no longer reported.

(The same behavior can be seen when using VS Code instead of running svelte-check directly.)

Logs

> omit-types-repro@0.0.1 check /home/five35/Documents/tmp/omit-types-repro
> svelte-kit sync && svelte-check --tsconfig ./tsconfig.json


====================================
Loading svelte-check in workspace: /home/five35/Documents/tmp/omit-types-repro
Getting Svelte diagnostics...

/home/five35/Documents/tmp/omit-types-repro/src/routes/+page.ts:3:14
Error: Type '() => { foo: string; }' is not assignable to type 'PageLoad'.
  Type '{ foo: string; }' is not assignable to type 'MaybePromise<Omit<PageData, never> & Partial<Pick<PageData, never>> & Record<string, any>>'.
    Type '{ foo: string; }' is not assignable to type 'Omit<PageData, never> & Partial<Pick<PageData, never>> & Record<string, any>'.
      Property 'bar' is missing in type '{ foo: string; }' but required in type 'Omit<PageData, never>'. 

export const load: PageLoad = () => {
  return { foo: "exists" };


====================================
svelte-check found 1 error and 0 warnings in 1 file
 ELIFECYCLE  Command failed with exit code 1.

System Info

System:
    OS: Linux 6.8 Ubuntu 24.04 LTS 24.04 LTS (Noble Numbat)
    CPU: (4) x64 Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz
    Memory: 2.64 GB / 7.63 GB
    Container: Yes
    Shell: 5.2.21 - /bin/bash
  Binaries:
    Node: 20.13.1 - ~/.local/share/asdf/installs/nodejs/20.13.1/bin/node
    Yarn: 1.22.22 - ~/.local/share/asdf/installs/nodejs/20.13.1/bin/yarn
    npm: 10.5.2 - ~/.local/share/asdf/plugins/nodejs/shims/npm
    pnpm: 9.5.0 - ~/.local/share/asdf/installs/nodejs/20.13.1/bin/pnpm
  npmPackages:
    @sveltejs/adapter-auto: ^3.0.0 => 3.2.2 
    @sveltejs/kit: ^2.0.0 => 2.5.18 
    @sveltejs/vite-plugin-svelte: ^3.0.0 => 3.1.1 
    svelte: ^4.2.7 => 4.2.18 
    vite: ^5.0.3 => 5.3.4

Severity

serious, but I can work around it

Additional Information

I'm new to Svelte and SvelteKit, so it's possible this is user error or expected behavior, but I wasn't able to find anything in the documentation or the blog article which indicates that the type of load should be anything other than PageLoad. (In fact, export const load: PageLoad = … is used in an example on the types page.)