Control flow breaks inside event handler lambda functions - intended or not?

[dummdidumm]

Control flow for TypeScript now should work correctly almost everywhere. One exception are event handlers when they use lambda functions.

To Reproduce

<script lang="ts">
  let value: string | null = null;

  function acceptsString(value: string) {
    console.log(value);
  }
</script>

{#if value}
  <!-- Argument of type 'string | null' is not assignable to parameter of type 'string'.
  Type 'null' is not assignable to type 'string'. -->
  <button on:click={() => acceptsString(value)} />
{/if}

Expected behavior
Now the question is: Is this a bug or standard TypeScript behavior?

One could argue it's a bug because one never gets to the click handler if the value is null.

One could also argue it's standard TypeScript behavior because the following React snippet will also yell at you:

function Component() {
    let value: string | null = null;

    function acceptsString(value: string) {
        console.log(value);
    }

    return value && <p onClick={() => acceptsString(value)}>
        Start editing to see some magic happen :)
    </p>;
}

The reason is that TypeScript does not know when that lambda-function is invoked, so it cannot say for sure that value has not changed in the meantime because it's not a const.

Thoughts on this welcome!

System (please complete the following information):
Svelte for VS Code 104.6.4 / svelte-check svelte-check-1.2.5

[pushkine]

The svelte syntax mimics if statements rather than conditionals
So if if (value) in Typescript narrows the type correctly, {#if value} should too

[Buraburaite]

One could argue it's a bug because one never gets to the click handler if the value is null.

I would agree. I am making a component that morphs based on the type of the provided variable, and I really expected that this would work.

Not my preference, but allowing for some kind of // @ts-ignore or as any would have been sufficient in my use case.

[dummdidumm]

#1657 and #1891 were opened with the same underlying reason, seeing it as a bug