Updating props passed via boolean operation break reactivity

Why this is a good first issue

Reactivity issue with boolean operations in props requires understanding Svelte's internals.

AI Summary

The issue reports a reactivity problem when passing boolean operations as props, with behavior differing between Svelte versions. The contributor needs to verify if this is a regression or expected behavior, but the exact scope is unclear due to conflicting playground examples. The main blocker is determining whether this is a bug or intentional behavior.

Issue Description

Describe the bug

Upgrading from svelte 5.20.0 to 5.46.3 I find some of my code lost reactivity due to prop update.

As described in doc https://svelte.dev/docs/svelte/$props#Updating-props

doing that is possible and the provided demo works well.

But in my code I pass a boolean operation to the child component instead of a boolean as in the example and it proven that it make a difference.

Reproduction

https://svelte.dev/playground/f5bec8a0be534b048f819df28bb3453c?version=5.46.3

Logs

System Info

System:
    OS: Linux 6.8 Ubuntu 24.04.3 LTS 24.04.3 LTS (Noble Numbat)
    CPU: (8) x64 Intel(R) Core(TM) i7-8665U CPU @ 1.90GHz
    Memory: 4.56 GB / 15.43 GB
    Container: Yes
    Shell: 5.2.21 - /bin/bash
  Binaries:
    Node: 24.12.0 - /home/loic/.nvm/versions/node/v24.12.0/bin/node
    npm: 11.6.2 - /home/loic/.nvm/versions/node/v24.12.0/bin/npm
  npmPackages:
    svelte: ^5.46.3 => 5.46.3 
    webpack: ^5.104.1 => 5.104.1

Severity

annoyance