Typescript support broken with TS 4.5, can't find type declarations

[phaer]

Hi,

I am trying to create a new svelte project with typescript support, but the build and dev scripts seem unable to find type declarations for App.svelte, even though src/global.d.ts seem to be correct:

/// <reference types="svelte" />

To Reproduce

~/projects 
❯ npx degit sveltejs/template svelte-app
> cloned sveltejs/template#HEAD to svelte-app

~/projects 
❯ cd svelte-app/ && node scripts/setupTypeScript.js
Converted to TypeScript.

~/projects/svelte-app via ⬢ v16.11.1 
❯ npm install && npm run build

added 135 packages, and audited 136 packages in 2s

11 packages are looking for funding
  run `npm fund` for details

found 0 vulnerabilities

> svelte-app@1.0.0 build
> rollup -c


src/main.ts → public/build/bundle.js...
(!) Plugin typescript: @rollup/plugin-typescript TS2307: Cannot find module './App.svelte' or its corresponding type declarations.
src/main.ts: (1:17)

1 import App from './App.svelte';
                  ~~~~~~~~~~~~~~

(!) Plugin typescript: @rollup/plugin-typescript: Typescript 'sourceMap' compiler option must be set to generate source maps.
created public/build/bundle.js in 1.3s

Node Version

❯ node --version
v16.11.1
❯ npm --version
8.1.3

[phaer]

When I manually add /// <reference types="svelte" /> to main.ts i get a new error:

(!) Plugin typescript: @rollup/plugin-typescript TS2688: Cannot find type definition file for 'svelte'.
src/main.ts: (1:23)
``

So I suppose type declarations are just missing in general? Any hint on where to find them?

[dummdidumm]

To rule out if it has to do with Typescript 4.5 which was just released: could you try to pin TS to 4.4 and try again?

[phaer]

@dummdidumm Thanks for your response and I can confirm it does work with typescript 4.4.4!

Additionally, I just was about to post that it also works with the following hardcoded path (with typescript 4.5)

/// <reference path="../node_modules/svelte/types/runtime/index.d.ts" />
import App from './App.svelte';

I am new to svelte and have been away from the whole JS ecosystem for a bit but will see if i find out more in typescripts changelog :)

[chrisolsen]

To rule out if it has to do with Typescript 4.5 which was just released: could you try to pin TS to 4.4 and try again?

This fixed the issue for me

[dummdidumm]

This is an TypeScript issue, I created microsoft/TypeScript#46860 for that. I also created sveltejs/svelte#6937 which would solve this independently on our end.

[dummdidumm]

This is fixed on our end through sveltejs/svelte#6937 , make sure to update to the latest version of Svelte and the error should go away. I still think this is a TS bug ultimately, but thankfully we can work around it with a change on our end. Closing.