TSTypeAssertion is not implemented by the Svelte compiler

[mazen-isstech]

Describe the bug

The Svelte compiler is not handling what the parser calls, TSTypeAssertion AST nodes.

About Typescript type assertions: https://www.typescriptlang.org/docs/handbook/2/everyday-types.html#type-assertions

Whenever the compiler encounters such a cast-expression, it throws the error:

Not implemented TSTypeAssertion

This is not a critical bug, but is an annoyance as sometimes a type checker is unable to deduce the true types of some expressions, which can cause several false positives. Casting is what help "patch" these issues.

Reproduction

https://svelte.dev/playground/hello-world?version=5.23.2#H4sIAAAAAAAAA22OywrCMBBFfyXOJi2IxW1MC-78B-OitmMNxGlIxhel_25iXbq7HO6ZuRNQe0NQcEDnRvEcg-tFgb1l7EtYw8U6jKCOE_Db514Gif-svfeb-EDHmZ3biP94NxIjcToDOnbBehaupaGWHGVjyLBDFllUInKwNIha6CU1opDfTbLcGdLVomeJ9HXbLKOn7M4rXSViKD1kfDEoDnecT_MH1_OZN-IAAAA=

Logs

None provided, see reproduction.

System Info

System and binaries are the same as https://svelte.dev/playground/ (console says it's running Svelte compiler version 5.23.2).

Browsers:
  Brave Browser: 134.1.76.74

Severity

annoyance

[Ocean-OS]

This isn't a direct bug in Svelte, rather it seems like a combination of bugs in both @sveltejs/acorn-typescript and esrap. I tried to make a fix, but there's some weird differences between acorn-typescript and @sveltejs/acorn-typescript that I can't resolve.
For now I'd recommend using TypeScript's as type assertion syntax, like so:

let name: string = 'world' as string;

[mazen-isstech]

@Ocean-OS Okay, I see. Anyway, thank you for the suggestion.