Assignments to new variable names in {#await} deconstruction are removed

[jesseskinner]

I'd like to do this:

{#await import('./Map.svelte') then { default: Map }}
    <Map />
{/await}

but it's being formatted to this:

{#await import('./Map.svelte') then { Map }}
    <Map />
{/await}

which doesn't work, because it's missing the default. If I save without formatting, it does work.