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In-Reply-To: <ce6a438b-9473-9b10-5475-a9a0f3deb72d@gmail.com>
Date: Sat, 16 May 2020 18:40:45 -0400
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Message-ID: <3576B8C4-D9E7-4C54-9D19-5F3ACDFF76F9@newclarity.net>
References: <ce6a438b-9473-9b10-5475-a9a0f3deb72d@gmail.com>
To: Pavel Patapau <algerd.blr@gmail.com>
Subject: Re: [PHP-DEV] [RFC] Guard statement
From: mike@newclarity.net (Mike Schinkel)

> On May 16, 2020, at 5:13 AM, Pavel Patapau <algerd.blr@gmail.com> =
wrote:
>=20
> Hello everyone,
>=20
> I want to propose new syntax addition - guard statement, that executes =
code only if expression equals false and must contain control-flow =
changing code, and written a respective RFC:
>=20
> https://wiki.php.net/rfc/guard_statement
> <https://wiki.php.net/rfc/unbundle_xmlprc>
>=20
> Implementation in progress.
>=20
> I started work before this proposal =
https://externals.io/message/110107 and respected some moments in the =
RFC.
>=20
>=20
> Thanks for consideration,
> Pavel


Many others have already made comments that I agree with so won't echo =
as they have already been said.

Two points:

1. That adding a `guard` would make it a reserved word is of significant =
concern to me, and looking at your examples I would ask why not simply =
ask that the if statement be able to omit the "true" block which could =
accomplish the same w/o needing to add another reserved word? e.g.

if (condition) else {
    //this code executed only if condition equals false
    return|throw|goto;
//or
   continue | break(in loop context only);
}

// in loop context - valid code
while (condition){
    if (condition) else {
        break; //valid
    }
}

Alternately, why not simply use what we already have, and what I do =
often, invert the condition?

if ( ! condition) {
    //this code executed only if condition equals false
    return|throw|goto;
//or
   continue | break(in loop context only);
}

// in loop context - valid code
while (condition){
    if ( ! condition ) {
        break; //valid
    }
}


Secondly, you reference this essay[1] which mentions why multiple =
returns are a bad idea, yet your proposal seems to want to encourage =
people to write more early returns, not fewer.

Regarding the multiple returns, consider the following, using an =
if(condition)else{} syntax AND assuming that we could add support for =
try{} without being required to use a catch():

function example() {
    try {
        $value =3D null;
        if (condition1) else {
            break;
        }
        if (condition2) else {
            break;
        }
        if (condition3) else {
            break;
        }
        $value =3D do_work();
    }
    return $value;
}


-Mike
[1] =
https://medium.com/@scadge/if-statements-design-guard-clauses-might-be-all=
-you-need-67219a1a981a=