From: Joseph Jones <joeyi5216@...>
Date: 2015-12-17T21:13:04-07:00
Subject: [ruby-core:72330] [Ruby trunk - Feature #10617] Change multiple assignment in conditional from parse error to warning

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Joseph Jones liked your message with Boxer. On December 10, 2015 at 11:05=
:50 MST, alxtskrnk=40gmail.com wrote:Issue =2310617 has been updated by b=
ug hit.Why hasn't this been accepted=3F There is no good reason that an e=
xpression that could be nil should not be testable.----------------------=
------------------=46eature =2310617: Change multiple assignment in condi=
tional from parse error to warninghttps://bugs.ruby-lang.org/issues/10617=
=23change-55449* Author: Recursive Madman* Status: Open* Priority: Normal=
* Assignee: ----------------------------------------There is currently an=
 inconsistency between regular and multiple assignment in conditionals.Re=
gular assignment causes a **warning**, multiple assignment causes a **par=
se error**.The historical reason for this is that in 1.8 multiple assignm=
ent would always return an Array, but since 1.9 it returns whatever the R=
HS evaluates to.**Examples:**=60=60=60rubya, b =3D nil =23=3D> nila, b =3D=
 =5B=5D =23=3D> =5B=5D (but a and b are both nil)a, b =3D 1,2 =23=3D> =5B=
1, 2=5D=60=60=60Since multiple assignment behavior has changed, it makes =
sense to remove the (artificial) parse error for multiple assignments.Tha=
t makes it possible to test the return value of a method used for multipl=
e assignment without having to use a temporary variable.**Example:**=60=60=
=60ruby=23 CURRENTLY WORKING CODE:tmp =3D some=5Fmethod=5Freturning=5Farr=
ay=5For=5Fnila, b =3D tmpif tmp =23 method returned an array (possibly em=
pty)else =23 method returned nil.end=23 PROPOSED WORKING CODE:if(a, b =3D=
 some=5Fmethod=5Freturning=5Farray=5For=5Fnil) =23 method returned an arr=
ay (possibly empty)else =23 method returned nilend=60=60=60(the parenthes=
is are needed due to LALR limitations, as discussed in =2310450)Attached =
is a patch that does the necessary change.---=46iles---------------------=
-----------0001-turn-parse-error-on-multiple-assignment-into-warning.patc=
h (752 Bytes)-- https://bugs.ruby-lang.org/     
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<html><body><div>Joseph Jones liked your message with <a href=3D=22http:/=
/bxr.io/PBIqo=22>Boxer</a>.</div><br/><br/><div><div class=3D=22quote=22>=
On December 10, 2015 at 11:05:50 MST, alxtskrnk=40gmail.com wrote:<br/><b=
lockquote type=3D=22cite=22 style=3D=22border-left-style:solid;border-wid=
th:1px;margin-left:0px;padding-left:10px;=22>Issue =2310617 has been upda=
ted by bug hit.<br /><br /><br />Why hasn't this been accepted=3F  There =
is no good reason that an expression that could be nil should not be test=
able.<br /><br />----------------------------------------<br />=46eature =
=2310617: Change multiple assignment in conditional from parse error to w=
arning<br />https://bugs.ruby-lang.org/issues/10617=23change-55449<br /><=
br />* Author: Recursive Madman<br />* Status: Open<br />* Priority: Norm=
al<br />* Assignee: <br />----------------------------------------<br />T=
here is currently an inconsistency between regular and multiple assignmen=
t in conditionals.<br />Regular assignment causes a **warning**, multiple=
 assignment causes a **parse error**.<br /><br />The historical reason fo=
r this is that in 1.8 multiple assignment would always return an Array, b=
ut since 1.9 it returns whatever the RHS evaluates to.<br /><br />**Examp=
les:**<br /><br />=60=60=60ruby<br />a, b =3D nil  =23=3D> nil<br />a, b =
=3D =5B=5D   =23=3D> =5B=5D     (but a and b are both nil)<br />a, b =3D =
1,2  =23=3D> =5B1, 2=5D<br />=60=60=60<br /><br />Since multiple assignme=
nt behavior has changed, it makes sense to remove the (artificial) parse =
error for multiple assignments.<br /><br />That makes it possible to test=
 the return value of a method used for multiple assignment without having=
 to use a temporary variable.<br /><br />**Example:**<br /><br />=60=60=60=
ruby<br />=23 CURRENTLY WORKING CODE:<br />tmp =3D some=5Fmethod=5Freturn=
ing=5Farray=5For=5Fnil<br />a, b =3D tmp<br />if tmp<br />  =23 method re=
turned an array (possibly empty)<br />else<br />  =23 method returned nil=
.<br />end<br /><br />=23 PROPOSED WORKING CODE:<br />if(a, b =3D some=5F=
method=5Freturning=5Farray=5For=5Fnil)<br />  =23 method returned an arra=
y (possibly empty)<br />else<br />  =23 method returned nil<br />end<br /=
>=60=60=60<br /><br />(the parenthesis are needed due to LALR limitations=
, as discussed in =2310450)<br /><br />Attached is a patch that does the =
necessary change.<br /><br /><br />---=46iles----------------------------=
----<br />0001-turn-parse-error-on-multiple-assignment-into-warning.patch=
 (752 Bytes)<br /><br /><br />-- <br />https://bugs.ruby-lang.org/<br /><=
/blockquote></div></div></body></html>
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