Cannot use records inside new `generics="T extends { key: string }"` attribute

[Nick-Mazuk]

Describe the bug

Using the new generics notation introduced in #2020, you cannot use records the generics attribute because the generics attribute is parsed as an HTML string, not as TypeScript code.

Reproduction

<script lang='ts' generics='T extends { foo: string }'>

</script>

Gives the error:

Error: Expected } (svelte)
<script lang="ts" generics="T extends { key: string }">

Expected behaviour

This entire string is parsed as JS and not as a string with interpolation.

System Info

• OS: macOS 13.3.1
• IDE: VS Code
• Svelte Check: 3.4.3

Which package is the issue about?

svelte-check

Additional Information, eg. Screenshots

There is a workaround, but I don't think this is ideal.

<script lang='ts' context='module'>
    type Foo = { foo: string }
</script>

<script lang='ts' generics='T extends Foo'>

</script>

[dummdidumm]

The record thing is a good catch, the Svelte parser thinks it's a mustache tag when it shouldn't. Mhm we may need to special-case this inside the parser, or add a change to the typescript preprocessor where it strips the generics attribute. The latter is now easily possible in Svelte 4, so that's probably the most promising route.

[janosh]

What's the official status of the generics attribute? Is $$Generic deprecated and the recommendation for everyone to start using generics? Having trouble piecing this together from GitHub threads. Maybe this could be clarified here https://svelte.dev/docs/typescript#experimental-advanced-typings.

[fedorovvvv]

Hey, guys!✨
Are you guys still working on this?

[kyrregjerstad]

Got the same issue, what's the recommended way to use $$Generic now?

[dummdidumm]

This is fixed in the latest version of Svelte 4. Update to it and the error should go away.