fix: access last safe value of prop on unmount (alternative)

[Rich-Harris]

Doesn't work with spreads yet

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🦋 Changeset detected

Latest commit: e19eb31

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[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@15366

[thes01]

Hi! Thanks for looking into this!

I've played a bit with the provided playground and I stumbled upon a curious case: https://svelte.dev/playground/4aff7feff74b4442a4d32f7de3b53e85?version=pr-15366

If you have a bindable prop and assign to it in onDestroy then although the prop change is propagated, the subsequent read is still the old value. This seems to be quite an edge case, but wanted to report that while the PR is being baked.

I guess it could make sense to disable mutating bindable props in the destroying state..?

[dummdidumm]

Closing since we merged another PR for this