`private` inside function arguments (field notation) about bun HOT 3 CLOSED

The shorthand also sets that variable in the class so you need to emit an assignment.

"use strict";
class Hello {
    constructor(hello) {
        this.hello = hello;
    }
    toString() {
        return this.hello;
    }
}

Source: https://www.typescriptlang.org/play?#code/MYGwhgzhAEASCmIQHtoG8BQ1vWMgdhAC4BOArsEciQBQAOJAlgG5hHzQAWiKAXNMSb4A5gEp0GLDgC+knNCoBlUoxE1xmefJLwiZEvgWdGEAHTckyANxTss6UA

from bun.

I see the problem.

The code does track this:

https://github.com/Jarred-Sumner/bun/blob/5537c03569e45bf73e490f58ac86d5cf661fa4ab/src/js_parser/js_parser.zig#L4417-L4428

But I forgot about the transform afterwards.

from bun.

Fixed in Jarred-Sumner/bun@d91e897

Currently, it follows the semantics of useDefineForClassFields which TypeScript enables by default when targeting ESNext or ES2022.

The following code:

class Testing {
  constructor(private hello: string) {}

  toString() {
    return this.hello;
  }
}

Now transpiles to:

class Testing {
  hello;
  constructor(hello) {
    this.hello = hello;
  }
  toString() {
    return this.hello;
  }
}

Note that there is a semantic difference when useDefineForClassFields is disabled with tsc. In that case, tsc removes the property from the class body. When useDefineForClassFields is disabled, tsc transpiles to:

class Testing {
    constructor(hello) {
        this.hello = hello;
    }
    toString() {
        return this.hello;
    }
}

Removing unitialized properties can cause a runtime performance problem when instantiating many objects of the same class due to polymorphism. However, for compatibility, it would be best if bun supports that anyway. The original issue was the build error due to private being used inside of function arguments though.

from bun.