onDestroy seems to hold a reference to an incorrect prop

[jkbz64]

Describe the bug

After splicing an array that is rendered with {#each} block, the onDestroy has a wrong reference to the prop, this can be observed in my reproduction - after clicking on remove we are removing an element from the middle of an array and onDestroy is called with x that corresponds to the last element of the array instead (?). After going out of flushSync last element's field is now undefined because of onDestroy (or null if onDestroy is not used).

Reproduction

https://svelte.dev/playground/1d048ad074c64ca586a46d3d8daecd83?version=5.20.5

Logs

We are splicing in the middle, why onDestroy has a reference to the last value?

System Info

System:
    OS: Linux 6.12 Fedora Linux Asahi Remix 41 (Forty One)
    CPU: (8) arm64 unknown
    Memory: 5.61 GB / 31.12 GB
    Container: Yes
    Shell: 5.9 - /usr/bin/zsh
  Binaries:
    Node: 18.20.4 - ~/.n/bin/node
    Yarn: 1.22.21 - ~/.n/bin/yarn
    npm: 10.7.0 - ~/.n/bin/npm
    pnpm: 10.2.1 - ~/.local/share/pnpm/pnpm
    bun: 1.2.4 - ~/.n/bin/bun

Severity

annoyance

[Prinzhorn]

Probably #14725

[paoloricciuti]

Yup, closing this as a duplicate