Remove `void` when using a setter from a class binding

[MangelMaxime]

Description

Can we remove the void from generated code or does it serve a purpose in this case?

It doesn't impact the performance but impact the bundle size and make the output less clean.

I think the void here protect from nothing.

Repro code

REPL](https://fable.io/repl/#?code=PYBwpgdgBAYghgIwDZgHQGFgCcwFgBQBA2gDwCSAtiNgC4AUARAMoCWA5hHDQK44ASYJCAYAaKAwBuAZwDGwACZgGASgB8AXQI0AnuCisOXXmAFC6yqAF4CUW1ApgKCMFigS4SKFPaceOKVAAXFAASmDeAF5gAIJYWHDaJMAIAFaqVlC+LBJgAPIQSNpQAO4sNAAWUGxgNGJSNTZ2Dk4uUAD6bajehn7hAExQjXZ2pRVVNVDmGVk5+YUkYZExcQlJqaqqQ8NQcBDyXhN0bUGh4SxRsfGJyWkWlplc2XkF2gQEKDRQOJ-3Br7GphA5gI3y6PiM-lQ0Xk8joEG4SCQyhBNTBPWMUj6UJhcIRSIIQA&html=Q&css=Q).

open Fable.Core

[<Import("SignatureHelp", "vscode")>]
type SignatureHelp() =
    member val signatures : ResizeArray<obj> = nativeOnly with get, set
    member __.signatures2 
        with get () = nativeOnly<ResizeArray<obj>>
        and set (_ : ResizeArray<obj>) = nativeOnly

let ret = SignatureHelp()
ret.signatures.Add(null)
ret.signatures2.Add(null)

generates

import { SignatureHelp } from "vscode";
import { defaultOf } from "fable-library/Util.js";

export const ret = new SignatureHelp();

void (ret.signatures.push(defaultOf()));

void (ret.signatures2.push(defaultOf()));

Related information

• Fable version: 4.1.3
• Operating system

[github-actions]

🤖 This is an automated response from Repo Assist.

The void wrapper around push() is intentional for TypeScript type-correctness.

In JavaScript, Array.prototype.push() returns number (the new array length). When Fable compiles an IList.Add call (which is void in F#), using void (array.push(item)) ensures the expression type matches void/undefined rather than number. Without it, TypeScript would report a type error when the result of Add is used in a typed position.

Relevant code is in src/Fable.Transforms/Replacements.fs — the "Add" case for mutable lists:

"void ($0)" |> emitExpr r t [ Helper.InstanceCall(ar, "push", t, [ arg ]) ]

This is a common pattern in the JavaScript target for methods that have a void return type in F# but a non-void return in their JavaScript equivalent. Removing the void would break TypeScript compilation for projects using strict type checking.

Note

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[MangelMaxime]

Yes, I think void is not so much an issue