chore: remove all references to callable, replace by closure

[azjezz]

Signed-off-by: azjezz azjezz@protonmail.com

[coveralls]

Pull Request Test Coverage Report for Build 1608969450

• 6 of 6 (100.0%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.0001%) to 99.881%

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Totals
Change from base Build 1608848542:	0.0001%
Covered Lines:	3355
Relevant Lines:	3359

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💛 - Coveralls

[veewee]

Any specific reason for accepting a less broad set of callbacks?

[bendavies]

@azjezz any reason for this change? making upgrading quite a chore :)

[bendavies]

i guess it's because of first-class callables in 8.1

map($api->getAll($params), [PostingPeriod::class, 'fromArray']);

becomes

map($api->getAll($params), PostingPeriod::fromArray(...));

[bendavies]

although we did have some callable classes (with __invoke) which we now can't use so nicely.
that needs:

before:

map($value, $this->foo);

after:

map($value, Closure::fromCallable($this->foo));

or

map($value, $this->foo->__invoke(...));

because this doesn't work:

map($value, $this->foo(...));

not very nice

[bendavies]

i'm an idiot.
this works:

map($value, ($this->foo)(...));

[azjezz]

The reasoning behind this change is in revolt-php, which uses Closure for all callbacks within the event loop, we can use Closure in async related functions, but that would be an inconsistency that i would rather avoid.