Using the default TypeScript package template:

1. Create a Component.svelte file and re-export it
2. In the component, import a module from filename.ts
3. The following import is kept as-is in the output (./dist)

import { module } from "./utilities.ts";

D:\_\DIST
    Component.svelte
    Component.svelte.d.ts
    index.d.ts
    index.js # index.ts does not exist
    utilities.d.ts
    utilities.js

4. The following import fails:

import Component from "../../dist/Component.svelte";

Failed to load url ./utilities.ts (resolved id: ./utilities.ts) in D:/_/dist/Component.svelte. Does the file exist?

The tsconfig.json was updated in #757

"allowImportingTsExtensions": true,