Allow type casting in @const declarations

[mnmr]

Describe the problem

I'm iterating an array and need to render sub-elements, so would like to have a {@const x = item.node.data} to make accessing the data part easier. However, I need to cast this to a subtype, and Svelte 5 currently rejects all attempts to do this inline:
{@const x: ISub = item.node.data}
{@const x = <ISub>item.node.data}
{@const x = item.node.data as ISub}

I was able to work around the issue by declaring a cast function, but that is not a nice experience:
function cast(node: INode): ISub { return <ISub>node.data; } {@const x = cast(item.node)}

Describe the proposed solution

Support additional syntax in the @const parser logic to enable inline casting.

Importance

would make my life easier

[7nik]

It works, and in VSCode as well.
Do you have lang="ts" on <script> or maybe you use another IDE?

[paoloricciuti]

I'll close this but feel free to reopen if it's an actual issue. Thanks for reporting!

[mnmr]

Sorry, I wasn't paying attention and missed the notifications. I'm using JetBrains Rider. It's absolutely an issue, though perhaps not in other IDEs.

[7nik]

JetBrains' Svelte plugin is known to still not have full Svelte 5 support.
I guess this issue is about this problem in the plugin.