Identifier xxx has already been declared

[Rich-Harris]

Describe the bug
If a reactive declaration is an assignment, Svelte automatically replaces $: with let in SSR mode if the variable on the left hand side hasn't been declared. It does this even if the left hand side is a member expression:

<script>
  $: user = {};
  $: user.name = 'world';
</script>

<h1>Hello {user.name}!</h1>

const App = create_ssr_component(($$result, $$props, $$bindings, $$slots) => {
  let user = {};
  let user.name = "world";
  return `<h1>Hello ${escape(user.name)}!</h1>`;
});

To Reproduce
https://svelte.dev/repl/b8f185ca9b104f4c8d08f2e5846cfaf0?version=3.24.1

Expected behavior
Only the $: user = ... declaration should have a let prepended.

Severity
Can be worked around (e.g. $: true && (user.name = 'world');) but it's a bit annoying. Relatively infrequent occurrence though.

[Conduitry]

In 3.25.0, the SSR output for this situation now only declares the variable once.