I'd like to note a couple of things ...
The behaviour of nullsafe and strict types being unspecified in the RFC would allow us to solve those problems later.
The behaviour of strict types right now is objectively wrong, the partial takes strictness from the application site, so as Nikita already knew when he asked the question; calls from a non-strict file will not behave as you expect.
With regard to the complexity in the implementation: I think it's important to understand that the complexity of the implementation is a product of the semantics we landed on during discussion.
The first implementation where we only had ? was technically simpler, but not intuitive from a user perspective.
Now we have semantics that are easy to understand, that you can communicate in a few lines. But the implementation is necessarily complicated as a result of those semantics.
We also have to remember that this is actually some kind of middle ground, it's not the most complicated version of partial application we could have - because that most complicated version would also include support for re-ordering parameters (named placeholders), and nor is it the simplest which offloaded a lot of (cognitive) overhead onto the programmer.
The question is not can we simplify the implementation, the question is rather, is the necessary complexity of an implementation with the kind of semantics that are desirable justified.
Cheers
Joe
On Mon, 21 Jun 2021 at 16:26, Björn Larsson via internals <internals@lists.php.net <
mailto:internals@lists.php.net>> wrote:
Den 2021-06-18 kl. 16:08, skrev Nikita Popov:
On Wed, Jun 16, 2021 at 6:17 PM Larry Garfield
<larry@garfieldtech.com <mailto:larry@garfieldtech.com>>
wrote:
Hi folks. The vote for the Partial Function Application RFC is
now open,
<https://wiki.php.net/rfc/partial_function_application>
Of particular note, a few people had asked about using ...?
instead of ...
for the variadic placeholder. In the end we decided not to
explore that,
as Nikita explained off-list it was actually more confusing,
not less, as
it would suggest "placeholder for a variadic" rather than "a
placeholder
that is variadic." Otherwise, it's just more typing. The
syntax choices
section of the RFC has been updated accordingly.
$foo?->bar(?)
is the same as $foo !== null ? $foo->bar(?) : null. I don't
think the
behavior is particularly unreasonable, but I also think it's not
particularly useful and may be surprising (in that there is a
plausible
alternative behavior). I think you may have been better off
forbidding that
case.
* The behavior of parameter names / reflection with regard to
variadic
parameters is very odd. For function test(...$args) and test(?,
?, ?) you
get back a function that nominally has three parameters with the
name
$args. Parameter names in PHP are generally required to be
unique, and of
course this also has implications for named arguments, for
example this
works, while it probably shouldn't:
https://3v4l.org/cQITD/rfc#focus=rfc.partials
<https://3v4l.org/cQITD/rfc#focus=rfc.partials> To be honest, I'm
not sure
what the right way to handle this is, but I don't think this is
it. A
possibility would be to bring back the concept of name-less
parameters we
had prior to PHP 8 (for internal functions only), or possibly to
make the
signature less precise by simply retaining an ...$args
parameter, and just
making the enforcement of "at least three parameters" an
implementation
detail. The latter seems like the best option.
* The RFC doesn't specify how PFA interacts with strict types.
If I create
a partially-applied function in strict_types=1 file and call it in a
strict_types=0 file, what happens? Will it use strict_types=0
semantics,
including for arguments that were bound in the strict_types=1 file?
* It's worth noting that the "new Foo(?)" syntax will create and
destroy a
Foo object as part of creating the partial (not just a call to the
partial). I've mostly convinced myself that this is *probably*
harmless. It
would have interacted negatively with an earlier version of
https://wiki.php.net/rfc/new_in_initializers
<https://wiki.php.net/rfc/new_in_initializers>, but I think the
problem there
was not on the side of partials.
In any case, I'm voting no on this one: While PFA is simple on a
conceptual
level, the actual proposal is complex and has lots of tricky
edge cases.
Especially once you take a look at the implementation. I'm not
convinced
that PFA in its full generality is justified for inclusion in PHP.
Regards,
Nikita
Would you look on this feature in a different light if the above
concerns about strict types and nullsafe calls could be clarified /
solved? Or is it about the implementation with it's complexity and
tricky edge cases?
I myself think one should take into account that this is a feature
that would make PHP stand out even more. Not being a follower of
other languages here :-)
Regards //Björn L
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