Scope issue in #await :catch causes exceptions or wrong behaviour

[Tharit]

Describe the bug
It seems that when an element within the :then block of an #await statement is updated after the first rendering, the error variable from the :catch block somehow "leaks" and overwrites other variables or causes an exception.

E.g. if you use {:catch error}, and the {:then} block also uses a variable named "error" things start to get weird.
In my actual application I have a "global" component variable named "error" that suddenly seems to hold the value of the awaited promise in some cases; and in other cases an exception is thrown within svelte.

To Reproduce
An exception will be triggered when clicking the button in this REPL; make sure to open e.g. Chrome Dev Tools before clicking the button.
The issue started in 3.25 - it worked fine with 3.24.1
https://svelte.dev/repl/95746deee9e34eb8b45a02a673e00136?version=3.37.0

Expected behavior
The naming of the error variable for the {:catch} block should not affect the :then block in any way; it should be scoped correctly.

Severity
Blocks update / would require renaming of variables in many component.

[jasonlyu123]

I also think this is a bug. In this repl the error variable is overridden by the resolved result of the promise. It only happens inside the await then block after an update happens.

I think the problem is with this line

svelte/src/compiler/compile/render_dom/wrappers/AwaitBlock.ts

Line 237 in 3b4d53e

update_child_context = b`#child_ctx[${this.then.value_index}] = #child_ctx[${this.catch.value_index}] = ${info}.resolved;`;

The variable with the same name is overridden

[Conduitry]

This should be fixed in 3.38.0 - https://svelte.dev/repl/95746deee9e34eb8b45a02a673e00136?version=3.38.0