Inconsistent bind:this value on svelte:component this=undefined

[mvolfik]

Describe the bug

{#if show}
  <svelte:component this={comp} bind:this={instance} />
{/if}

Start with show=true, comp=Foo. Instance correctly contains the props and state of the component. Now do comp=undefined (or any falsy value, according to docs), the component is unmounted from DOM, state is removed from the instance object, but the rest (such as export function and various internal methods) remains on the object from the last comp before the falsy value.

In the repl linked below, this is checked by calling the exported function - in console you can see it repeatedly logging.

Now if you do show=false, the component is uninitialized and instance becomes null - same as when you have a normal component with bind:this. Now if you do show=true again, instance remains null, until you change comp to an actual component again.

I'd expect that the component should be fully removed and bind:this={instance} set to null as soon as the this={comp} is unset (set to falsy value).

---

Related to #1489 (old, then fixed - was svelte v2?)

Reproduction

https://svelte.dev/repl/c477b15230e347e19436325f2589665c?version=3.43.2

Logs

No response

System Info

Repl: v3.43.2

  System:
    OS: Linux 5.4 Ubuntu 20.04.3 LTS (Focal Fossa)
    CPU: (4) x64 Intel(R) Core(TM) i3-3110M CPU @ 2.40GHz
    Memory: 227.30 MB / 7.35 GB
    Container: Yes
    Shell: 3.1.0 - /usr/bin/fish
  Binaries:
    Node: 14.18.1 - /usr/bin/node
    Yarn: 1.22.11 - ~/.local/bin/yarn
    npm: 7.24.1 - ~/.local/bin/npm
  Browsers:
    Chromium: 94.0.4606.81
    Firefox: 93.0
  npmPackages:
    svelte: ^3.43.2 => 3.43.2 
    vite: ^2.6.7 => 2.6.7

Severity

annoyance