Useless empty class fields are generated when using parameter properties and target=ESNext

[angryziber]

Bug Report

  class MenuItem {
    constructor(public name: string) {}
  }

Compiling this with -t ESNext produces:

class MenuItem {
    name;
    constructor(name) {
        this.name = name;
    }
}

The name field above also confuses some next stage build tools that don't support class fields yet, e.g. the popular acorn that is used by Svelte compiler (sveltejs/svelte#6592)

However, compiling with -t ES2021 produces more compact code without useless field declaration:

class MenuItem {
    constructor(name) {
        this.name = name;
    }
}

🔎 Search Terms

constructor shorthand

🕗 Version & Regression Information

Version 4.3.5 & next

• This changed between versions 4.2.x and 4.3.x

[IllusionMH]

ESNext uses useDefineForClassFields by default
See #45076

[fatcerberus]

Just to add because I feel this is important: in an environment that natively supports class fields, the declared field is not useless - behavior actually differs between the two snippets because ECMAScript dictates [[Define]] semantics for fields.

[typescript-bot]

This issue has been marked as 'Question' and has seen no recent activity. It has been automatically closed for house-keeping purposes. If you're still waiting on a response, questions are usually better suited to stackoverflow.