Regression: reactive variables inside brackets raise an error

[dkzlv]

Describe the bug
Reactive variables appear to be unassigned to the compiler, if you define them in a reactive block with curly braces, both in template and in script tag.

To Reproduce

<script lang="ts">
  export let check: boolean;

  let derived: string;
  $: {
    derived = check.toString();
  }

  // Variable 'derived' is used before being assigned.
  console.log(derived.toUpperCase())
</script>

<!-- Variable 'derived' is used before being assigned. -->
{derived.toUpperCase()}

Expected behavior
Shouldn't report any errors here.

System (please complete the following information):
OS: Mac OS 10.15.3
IDE: VS Code
Plugin/Package: Svelte for VS Code (the new official one)

Additional context
Used to work a week ago. It works fine if you change the syntax to $: derived = ... without the brackets.
Also, svelte-check doesn't report any errors here.

[jasonlyu123]

the one in the script is correct. I'll see what we can do about the one in the template

[dkzlv]

Same goes for other cases like this:

let sliceStart: number, sliceEnd: number;
$: [sliceStart, sliceEnd] = [page * limit, page * limit + limit];

It also says these two variables are used before assigning.

[jasonlyu123]

This raises another problem

let d = 1;
$: a = d;
console.log(a)

The console.log(a) is used before declare because the compiler moves all the reactive to after no-reactive. So this should also show an error

https://svelte.dev/repl/1001568f2498473bbfb665129876259b?version=3.24.0

[jasonlyu123]

Let's track the used before declare in a separate issue