Strict switch

On Thu, Nov 26, 2020 at 10:39 AM David Rodrigues david.proweb@gmail.com
wrote:

With PHP 8 we have match(), that is a switch strict expression-like. But
strict is not strict, and it could cause confusion because switch() and
match() are pretty similar.

I agree that PHP deserves the ability to do strict comparisons when
requested and that match won't serve all of switch's use cases. This idea
has come up a few times in the past, but I think we can perhaps get further
with it now that the language is growing more strict-friendly.

(1) strict switch(8.0) { case '8.0'; return 'no'; case 8.0: return 'yes'; }
// yes

Introducing new keywords automatically has a higher bar to acceptance than
not, so while this certainly reads well, we do have to consider the impact
to existing code defining clases/functions named 'strict'.

(2) switch strict(8.0) { ... } // yes
(3a) switch(8.0, true) { ... } // yes

I'm not a fan of how either of these read. The first on wholly aesthetic
grounds, the latter on opacity. The meaning of "true" is inobvious here.

(3b) switch(8.0, strict: true) { ... } // yes (named argument)

This I like now that we have named arguments. It's a psuedo named
argument, but I don't think that distinction matters too much from the
userland perspective. Implementation might be a little on the ugly side
though, so let's keep it in the maybe pile.

Or then in the "case":

(4) switch(8.0) { strict case 8.0: ... } // yes
(5) switch(8.0) { case strict 8.0: ... } // yes

Or allowing operators (this would be the most flexible way, as it would
allow for a number of other features):

(6) switch(8.0) { case === 8.0: ... } // yes

These formats have been proposed previously, and I think they're the worst
of the lot because now you have a comparison that is potentially sometimes
strict and sometimes not. This has the highest potential for surprise.

The main question I'd put to you is this: Are there other parts of the
language where a strictness modifier would also make sense, or is it unique
to switch. I suspect it's not, so list out those syntaxes and identify
how the proposed options would translate to them. A general purpose winner
may float itself to the top.

-Sara

On Thu, Nov 26, 2020 at 5:39 PM David Rodrigues david.proweb@gmail.com
wrote:

Hello!

With PHP 8 we have match(), that is a switch strict expression-like. But
strict is not strict, and it could cause confusion because switch() and
match() are pretty similar.

I believe that this has already been discussed, but it would be interesting
to re-evaluate the possibility of a strict() with support for strict.

In order not to generate BC, my suggestion is to attach a specific keyword
for this purpose, or a similar alternative.

(0) switch(8.0) { case '8.0'; return 'no'; case 8.0: return 'yes'; } // no?

(1) strict switch(8.0) { case '8.0'; return 'no'; case 8.0: return 'yes'; }
// yes
(2) switch strict(8.0) { ... } // yes
(3a) switch(8.0, true) { ... } // yes
(3b) switch(8.0, strict: true) { ... } // yes (named argument)

Or then in the "case":

(4) switch(8.0) { strict case 8.0: ... } // yes
(5) switch(8.0) { case strict 8.0: ... } // yes

Or allowing operators (this would be the most flexible way, as it would
allow for a number of other features):

(6) switch(8.0) { case === 8.0: ... } // yes

Atenciosamente,
David Rodrigues

I think the better direction here would be to improve match() such that it
can replace more of the current switch use cases. If match supported block
expressions, then most uses of switch() could use match() instead, and as
such make use of the strict comparison semantics. Only switches that make
use of non-trivial fallthrough behavior could not be easily expressed using
match.

Nikita