Support new svelte $$Generic type

[SomaticIT]

Hello,

A couple of months ago (July 2021), the Svelte team added the ability to specify generics types when using TypeScript.

RFC: sveltejs/rfcs#38
Thread: sveltejs/language-tools#442

Exemple

<!-- ForEach.svelte -->
<script lang="ts">
  type T = $$Generic;
  export let items: T[];
</script>

{#each items as item}
  <slot {item} />
{/each}

<!-- App.svelte -->
<script lang="ts">
  import ForEach from "$lib/components/ForEach.svelte";
  import type { Todo } from "$lib/todo.service";

  let todos: Todo[] = [];
</script>

<ForEach items={todos} let:item>
  <!-- item is correctly typed as Todo here -->
  <p>{item.name}</p>
</ForEach>

Issue

When using this new feature, eslint-plugin-svelte3 complains with error no-undef.

Workaround

Disabling the error manually:

<script lang="ts">
  type T = $$Generic; /* eslint-disable-line no-undef */
  export let items: T[];
</script>

{#each items as item}
  <slot {item} />
{/each}

[Conduitry]

Your fix has been released as 3.2.1. Thank you!

[SomaticIT]

Happy to help! Thank you

[wvhulle]

So this feature has been removed in the successor of the parser. Is it a good idea to revert to this version while it is not reimplemented yet?

sveltejs/svelte-eslint-parser#306