fix(cdk/testing): require at least one argument locator functions

[crisbeto]

Currently the locator functions are written with a single rest parameter which means that no arguments can be passed as well, even though it'll result in an error at runtime.

These changes rework the type so that at least one argument is required to be passed in.

[devversion]

Nice! Oh, CI is red?

[crisbeto]

Yeah, looks like this doesn't handle mixed usages very well. I'll see if I can work around it.

[crisbeto]

It looks like typing mixed arguments isn't possible :(. Closing the PR.

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[mmalerba]

I believe you can accomplish this by having T extend a more specific array: https://www.typescriptlang.org/play?#code/GYVwdgxgLglg9mABMAPAFUQUwB5U2AEwGdEBtMEAWwCNMAnAGkQDpWKb7SBdLgPgApWzAIZ0A5kQBciNAEppGAN4AoRIjqYoIOklESA3MoC+y5cH6zD5gIyWz-a0wBMdoA

[crisbeto]

I just gave it a shot, but I'm not sure it's what we want either. We'd need to allow something like (A | B)[] for both the rest parameter and the first one, but it requires that the first one is A (number in this case).

[mmalerba]

I think the same pattern still works? Just change number to the union you want. e.g. here's a string | number example: https://www.typescriptlang.org/play?#code/GYVwdgxgLglg9mABMAPAFUQUwB5U2AEwGdEBtACiKgCcYwBzRAHzBAFsAjTagSgBpEAOmGUadRk0StO3HqQC68gHzlhggIbV6RAFyI0PPRgDeAKESJqmKCGpJN2gNymAvqdPByPZ54CM3j3JfAQAmAL8BAHIoAHc4SJ5TIA

[crisbeto]

Nice, that one works as expected! Here's a PR to implement it #23619.