All Typescript features that modify code are broken

[ottomated]

Describe the bug

Typescript features such as constructor field initializers are broken in 5.0.0-next.240

class X {
  constructor(public foo) {}
}

// transpiles to
class X {
  constructor(foo) {}
}

// should transpile to
class X {
  constructor(foo) {
    this.foo = foo;
  }
}

Reproduction

REPL

Logs

No response

System Info

System:
    OS: Linux 6.10 Fedora Linux 40 (Forty)
    CPU: (32) x64 AMD Ryzen 9 5950X 16-Core Processor
    Memory: 50.96 GB / 62.70 GB
    Container: Yes
    Shell: 3.7.0 - /bin/fish
  Binaries:
    Node: 20.12.2 - ~/.volta/tools/image/node/20.12.2/bin/node
    Yarn: 4.3.1 - ~/.volta/tools/image/yarn/4.3.1/bin/yarn
    npm: 10.5.0 - ~/.volta/tools/image/node/20.12.2/bin/npm
    pnpm: 9.7.0 - ~/.volta/bin/pnpm
    bun: 1.1.20 - ~/.bun/bin/bun
  npmPackages:
    svelte: 5.0.0-next.240 => 5.0.0-next.240

Severity

blocking all usage of svelte

[dummdidumm]

Closing as duplicate of #11502 - we need to error on cases that we cannot/won't transpile, and try to transpile others that are possibly more straightforward. Silent errors like this are bad, I agree

[ottomated]

This was only recently broken so it seems like a regression, unless it was only unintentionally working before?

[dummdidumm]

This is likely because vite-plugin-svelte changed its default from preprocessing script tags to not preprocessing them. You can reenable that and it will work again https://github.com/sveltejs/vite-plugin-svelte/blob/main/docs/preprocess.md

cc @dominikg - it looks like the docs aren't updated yet to show the changed default?