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Invalid mutation or binding when modifying array elements #11861

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@GuyShane

Description

@GuyShane

Describe the bug

I'm getting either an ownership_invalid_mutation or ownership_invalid_binding warning from the compiler when I try to modify array elements of shared state passed through a context.

The warnings aren't given when modifying base properties of the context, only for elements of arrays.

The first happens if I try to do something like the following and bind to the element directly

{#each array as elem}
    <Child bind:elem />
{/each}

And the second if I try to pass the index and modify the element

{#each array as _elem, idx}
    <Child {idx} />
{/each}

What would be the correct way to modify elements of an array using shared state?

Reproduction

https://stackblitz.com/edit/stackblitz-starters-kks8ef?file=src%2Froutes%2F%2Bpage.svelte

This is a minimal reproduction of both techniques using [email protected]

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System Info

System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 18.20.3 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.2.3 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    svelte: ^5.0.0-next.1 => 5.0.0-next.148

Severity

annoyance

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