--tsgo: .svelte files imported through package.json imports (e.g. Kit 3 #lib/*) resolve to the ambient *.svelte shim #3142

Describe the bug

With --tsgo, a .svelte file imported through a package.json imports (subpath import) alias, such as SvelteKit 3's #lib/*, resolves to the ambient declare module "*.svelte" shim instead of the emitted .svelte.ts overlay. Named exports from <script module> then fail with TS2614, and component props become any, so every callback parameter reports TS7006. The same component imported by a relative path in the same file is typed correctly, and the default mode (no --tsgo) reports nothing.

This looks like the package.json#imports counterpart of #2952 (fixed for tsconfig paths in #2955). SvelteKit 3 replaced $lib (a paths alias) with #lib (a subpath import), so every Kit 3 app that imports components as #lib/…​.svelte hits it. In our app (556 .svelte files, Kit 3.0.0) --tsgo reports 103 false errors and the default mode reports 0.

Reproduction

package.json:

{
  "name": "svelte-check-tsgo-subpath-imports",
  "private": true,
  "type": "module",
  "imports": { "#lib/*": "./src/lib/*" },
  "devDependencies": {
    "svelte": "5.57.1",
    "svelte-check": "4.7.6",
    "typescript": "npm:@typescript/typescript6@6.0.2",
    "@typescript/native": "npm:typescript@7.0.2"
  }
}

tsconfig.json:

{
  "compilerOptions": {
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "bundler",
    "strict": true,
    "noEmit": true,
    "types": ["svelte"]
  },
  "include": ["src/**/*.ts", "src/**/*.svelte"]
}

src/lib/Counter.svelte:

<script module lang="ts">
  export const STEP = 1;
</script>

<script lang="ts">
  let { label, onpick }: { label: string; onpick: (value: number) => void } = $props();
</script>

<button onclick={() => onpick(STEP)}>{label}</button>

src/App.svelte:

<script lang="ts">
  import Counter, { STEP } from "#lib/Counter.svelte";
  import Relative, { STEP as RELATIVE_STEP } from "./lib/Counter.svelte";
  let total = $state(STEP + RELATIVE_STEP);
</script>

<Counter label="via #lib" onpick={(value) => (total += value)} />
<Relative label="relative" onpick={(value) => (total += value)} />
<p>{total}</p>

Then:

$ npx svelte-check --tsconfig ./tsconfig.json
svelte-check found 0 errors and 0 warnings

$ npx svelte-check --tsconfig ./tsconfig.json --tsgo
src/App.svelte:2:21
Error: Module '"*.svelte"' has no exported member 'STEP'. Did you mean to use 'import STEP from "*.svelte"' instead? (ts)

src/App.svelte:7:36
Error: Parameter 'value' implicitly has an 'any' type. (ts)

svelte-check found 2 errors and 0 warnings in 1 file

Both errors are on the #lib import and its usage (lines 2 and 7). The relative import of the same file (lines 3 and 8) is clean.

--tsgo-experimental-api handles this case correctly (0 errors), so only the overlay-tsconfig --tsgo / --incremental path is affected.

Expected behaviour

The same result as the default mode: subpath-import specifiers that map to a .svelte file resolve to its emitted overlay, the way relative and paths-alias specifiers do after #2955.

System Info

• svelte-check 4.7.6, svelte 5.57.1
• typescript 6.0.2 (via @typescript/typescript6), @typescript/native = typescript 7.0.2
• Node 26.10.0, Linux x64

Which package is the issue about?

svelte-check

Additional Information, eg. Screenshots

From reading incremental.ts, it looks like the overlay tsconfig only rebases compilerOptions.paths (rebasePathsConfig). A package.json imports target such as ./src/lib/* is resolved by TypeScript straight to the source .svelte file, which never matches an emitted .svelte.ts, so resolution falls through to the ambient module.