Old alias syntax accepts "ref"

[dlangBugzillaToGithub]

Dicebot (@mihails-strasuns) reported this on 2013-11-28T07:29:22Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=11632

CC List

• Maxim Fomin
• Bolpat
• Robert Schadek

Description

When using old alias form, `ref` is both accepted and not making any effect:

-----------
alias ref int RefInt;

void foo(RefInt x)
{
	x = 42;
}

void main()
{
	int x;
	foo(x);
	
	import std.stdio : writeln;
	writeln(x);
}
-----------
0
-----------

`alias RefInt = ref int` is rejected with "Error: basic type expected, not ref" so I assume it should be the same here.

[dlangBugzillaToGithub]

maxim commented on 2013-11-28T07:46:39Z

More nonsense:

alias ref int ri;
//alias in int ii;
alias int oi;
//alias lazy int li;
//alias out int outi;

alias pure int pi;
alias @safe int si;
//alias trusted int ti;
alias nothrow int nthi;

alias auto int ai;
alias @property int pri;
alias @disable int di;
alias scope int sci;

alias align(16) int ali;

alias abstract int absi;

alias final int fi;
alias override int ovi;
alias inout int inoui;
alias synchronized int syi;

alias static int stati;

It is unclear however, whether this is a part of major accepts-invalid bug (dmd is permissive in allowing to apply attributes to declarations, so here is particular case) or defficiency in old alias syntax parsing.

[dlangBugzillaToGithub]

public (@mihails-strasuns) commented on 2013-11-28T07:52:06Z

Whatever it is, current behavior is extremely confusing for newbies as one may expect it to actually work in example like provided in the first post.

[dlangBugzillaToGithub]

bearophile_hugs commented on 2013-11-28T08:02:54Z

See also Issue 3934

[dlangBugzillaToGithub]

andrej.mitrovich (@AndrejMitrovic) commented on 2014-04-22T21:17:36Z

*** Issue 12299 has been marked as a duplicate of this issue. ***

[dlangBugzillaToGithub]

andrej.mitrovich (@AndrejMitrovic) commented on 2014-04-22T21:17:49Z

*** Issue 12257 has been marked as a duplicate of this issue. ***

[dlangBugzillaToGithub]

rburners commented on 2015-06-04T02:30:13Z

phobos PR https://github.com/D-Programming-Language/phobos/pull/2995

is sort of blocked by:

template RefType(T) alias RefType = ref T;

not working anymore

[dlangBugzillaToGithub]

qs.il.paperinik commented on 2021-01-10T00:24:27Z

The grammar allows this to make

alias RefDG = ref int delegate();

legal. Having ref be accepted but with no effect is nothing special about the D compiler. It accepts a lot of annotations that have no effect.

The question which cases are accepts-invalid and which are not is mostly a matter of taste.