V11 & V12 - Fails to set value to nested optional mutable field

[DZakh]

https://rescript-lang.org/try?version=v11.1.4&module=esmodule&code=C4TwDgpgBAdhDOwIBMoF4oG8C2BXYAhgEYA20AZgJYQnID8AXFJTMAL4BQokUA5gE4B7XGHRY4iFEwlJknDmWB8hIpgOGiMmGVKxt5iqORhjE-dAD4sHKMo0A6HcntUaqDGYC0FgJKsXQtgAysD8LLwcnEA

You can see how there's no field assignment in the code.

[nojaf]

Workaround is too add mutable as well to the parent?

[cristianoc]

Here's an example that does not use mutable at all:

type nested = {field?: int}
type pair = (nested, string)

let p: pair = ({}, "")


let x = fst(p)
let y = fst(p)

Gives:

let p = [
  {},
  ""
];

let x = {};

let y = {};

So it seems that the initialisation {} is inlined or something, which loses the alias between x and y (and w.r.t the first component of p).

[cristianoc]

Here's a tweaked example that does not use optional fields at all:

type record = {field: int}
type pair = (record, string)

let p: pair = ({field:2}, "")


let x = fst(p)
let y = fst(p)

and shows the duplication of the record value:

let p = [
  {
    field: 2
  },
  ""
];

let x = {
  field: 2
};

let y = {
  field: 2
};