Allow Dispatchers to be cached

[eric-wieser]

This allows functions which take callable arguments to be cached

Closes #6251

[esc]

@eric-wieser thanks for submitting this, I have queued it for review.

[richardsheridan]

I just tried this patch on some of my higher-order functions and it doesn't crash 👍 but I was noticing a hiccup remaining on my first call to the cached functions. I looked into my __pycache__ folder and it looks like the cache is missing once each new process for the higher-order functions only. Possibly the cache is missing because the dispatcher hashes are not stable across startups for some reason?

[stuartarchibald]

I just tried this patch on some of my higher-order functions and it doesn't crash +1 but I was noticing a hiccup remaining on my first call to the cached functions. I looked into my __pycache__ folder and it looks like the cache is missing once each new process for the higher-order functions only. Possibly the cache is missing because the dispatcher hashes are not stable across startups for some reason?

Thanks for testing this. xref: #6284 is probably also needed.

[eric-wieser]

Is the plan to wait until @6284 is sorted before putting this in, or are they fine to go in indepedently?

[stuartarchibald]

Thanks for debugging and fixing this, one minor stylistic thing to resolve else good to go.

[stuartarchibald]

Is the plan to wait until @6284 is sorted before putting this in, or are they fine to go in indepedently?

Think they can go in independently, but we may need to update tests.

[stuartarchibald]

Thanks for the fix-ups!