Infinite loop error in REPL when using generators

[BillyLevin]

Describe the bug
Using a generator on the Svelte REPL gives an error: "Infinite loop detected". Nothing seems to freeze and the code works fine when I run it in my own repo. I'm not sure if the error message is incorrect or if Svelte does something with generators/iterators that I'm not aware of.

Logs
This is the log from the REPL linked in the next section

To Reproduce
Create a generator and call the next() method on it inside a button onclick function. Click the button a couple of times and you'll get the error message. Here is a basic example where I'm updating some simple state:

https://svelte.dev/repl/6d6346405cbd4267b82c53aa0218f536?version=3.20.1

Expected behavior
There shouldn't be an infinite loop error

Information about your Svelte project:

• Browser: Chrome 80

• OS: Windows 10

• Svelte version: 3.20.1 (current REPL version)

Severity
How severe an issue is this bug to you? Is this annoying, blocking some users, blocking an upgrade or blocking your usage of Svelte entirely?

Not severe at all as my code seems to work outside of the REPL. I'd mostly like to make sure I'm not doing something wrong :)

Thanks!

[pushkine]

the loopguard is timeout based so it's not compatible with generators
I can't think of a way to fix this other than counting iterations

[BillyLevin]

Hey, thanks for the response!

After digging into ESTree a little, I think I found a way to opt out of loop_protect for generators. I'll submit a PR tomorrow :)

[Conduitry]

This has been fixed in 3.22.0 - https://svelte.dev/repl/6d6346405cbd4267b82c53aa0218f536?version=3.22.0