On Mon, 23 May 2016 22:52:18 +0300, Levi Morrison <le...@php.net> wrote:
On Mon, May 23, 2016 at 1:19 PM, Nikita Nefedov <inefe...@gmail.com>
wrote:
On 23 May 2016, at 19:31, Levi Morrison <le...@php.net> wrote:
A quick question before I vote: do callable prototypes allow for
default parameters in the signature? There are examples for having a
function passed that has a default parameters but I am not seeing it
anywhere in the callable prototype definition so I thought I'd ask.
Hey Levi,
Although it could be done as a later RFC, my stance on it is that
default values don't belong to the prototype of the function.
Why I think that callable typehint doesn't need default values for
params is: you either need this parameter to exist and even if there
are cases where you'd like to pass some kind of 'default' value
implicitly, you as a caller shouldn't impose on the callee
responsibility to have this same value in his definition and instead
just pass your argument explicitly... or if you don't need this
parameter (as in you don't plan to pass anything explicitly) then you
should just ask for a function without this parameter as there is
clearly no need for it at all.
Moreover I would argue interfaces have it wrong here too: the fact that
default values are part of an interface yet their invariance is not
enforced, yields an interesting sort of possible LSP violation. F.e. if
we have an interface Logger (a completely unreal example but it shows
what can go wrong) with function 'log($message, $level = LOG_DEBUG);'
and a funny implementation that decided to change default value of
$level to LOG_ALERT, then all callers of Logger#log who relied on the
fact that level if not specified, will be LOG_DEBUG, who also happen to
get the funny implementation of Logger will produce unneeded noise in
the logs with their alert level messages which were intended to be
debug messages :(
Please document this restriction in the RFC. I guess I'm the only one
who expected it to be there since it didn't come up before, but it
just seems missing. You don't need to take it out of voting for this
clarification, imo.
Morning,
sure thing, added it in the RFC
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