[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123 Andrei Alexandrescu changed: What|Removed |Added CC||and...@erdani.com --- Comment #8 from Andrei Alexandrescu --- subscribe --
[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123 Nick Treleaven changed: What|Removed |Added CC||n...@geany.org See Also||https://issues.dlang.org/sh ||ow_bug.cgi?id=6842, ||https://issues.dlang.org/sh ||ow_bug.cgi?id=14128 --
[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123 --- Comment #9 from Nick Treleaven --- > S s; > alias y = s.x; // note, this compiles just fine, you need to use it to flag > the error. This is an error in the next edition: https://dlang.org/spec/legacy#alias-instance-member https://github.com/dlang/dmd/pull/15863 --
[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123 Ketmar Dark changed: What|Removed |Added CC||ket...@ketmar.no-ip.org --
[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123
--- Comment #1 from Sobirari Muhomori ---
I guess, you can alias a symbol, but then the compiler doesn't know what S's
symbol in T struct means.
struct S
{
int x;
alias y = x;
}
actually means
struct S
{
int x;
alias y = S.x;
}
struct T
{
S s;
alias y = S.x; // what this means?
}
--
[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123
--- Comment #2 from Steven Schveighoffer ---
(In reply to Sobirari Muhomori from comment #1)
> struct T
> {
>S s;
>alias y = S.x; // what this means?
> }
Right, but I said s.x, not S.x. It means alias to the member x of the instance
of S called s, which resides in this instance of T.
Maybe it's more helpful if I say:
alias y = T.s.x;
In any case, I see no technical limitation of why this shouldn't work. If
there's already a way to do it, please close and let me know how to!
Note, I've worked around in my code by doing essentially:
private ref y() { return s.x; }
But I much prefer the alias mechanism.
--
[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123
Max Samukha changed:
What|Removed |Added
CC||maxsamu...@gmail.com
--- Comment #3 from Max Samukha ---
(In reply to Steven Schveighoffer from comment #2)
> (In reply to Sobirari Muhomori from comment #1)
>
> > struct T
> > {
> >S s;
> >alias y = S.x; // what this means?
> > }
>
> Right, but I said s.x, not S.x. It means alias to the member x of the
> instance of S called s, which resides in this instance of T.
In 'alias', they are just two equivalent ways of referencing 'x', that is:
__traits(isSame, S.x, T.s.x) == true
And it kind of makes sense if you think of 'alias' as little more than a means
of creating synonyms for a symbol. With 's.x' in the 'alias' declaration, you
are simply importing 'x' to the namespace of 'T'. Not that I care much now, but
some code I wrote actually relied on this semantics.
--
[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123 --- Comment #4 from Steven Schveighoffer --- I'm having trouble seeing how this logically is different. Access to t.s.x is done by adding some offset to &t, just like access to s.x is done by adding some offset to &s. I get that the "symbol" I'm trying to alias is really a compound symbol, but I can alias it just fine in other places. This reminds me of the whole inability to alias keywords. It's an implementation detail that I shouldn't have to care about! --
[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123 --- Comment #5 from Max Samukha --- (In reply to Steven Schveighoffer from comment #4) > I'm having trouble seeing how this logically is different. Access to t.s.x > is done by adding some offset to &t, just like access to s.x is done by > adding some offset to &s. > > I get that the "symbol" I'm trying to alias is really a compound symbol, but > I can alias it just fine in other places. I just say that what you are trying is not how 'alias' works, and the current semantics does make sense. Whether it is good is a different issue. > > This reminds me of the whole inability to alias keywords. It's an > implementation detail that I shouldn't have to care about! Inability to alias keywords is a different issue. --
[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123 --- Comment #6 from Steven Schveighoffer --- (In reply to Max Samukha from comment #5) > (In reply to Steven Schveighoffer from comment #4) > > I'm having trouble seeing how this logically is different. Access to t.s.x > > is done by adding some offset to &t, just like access to s.x is done by > > adding some offset to &s. > > > > I get that the "symbol" I'm trying to alias is really a compound symbol, but > > I can alias it just fine in other places. > > I just say that what you are trying is not how 'alias' works, and the > current semantics does make sense. Whether it is good is a different issue. I would understand if s was a property and not a field, because you need to execute code to compute the actual access. I get that alias is not as powerful as a mixin, but this doesn't seem like a reasonable limitation. Note: it's kind of weird that the compiler would allow this kind of alias to compile when it's fully unusable. > > This reminds me of the whole inability to alias keywords. It's an > > implementation detail that I shouldn't have to care about! > > Inability to alias keywords is a different issue. To the user, it's not much different. Granted, two different implementation issues, but it looks the same -- compiler cannot do what should be obviously doable. --
[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123 Steven Schveighoffer changed: What|Removed |Added Severity|normal |enhancement --- Comment #7 from Steven Schveighoffer --- (In reply to Max Samukha from comment #5) > I just say that what you are trying is not how 'alias' works, and the > current semantics does make sense. Whether it is good is a different issue. However, I get your point that this is intended behavior and working as designed. I'm changing to enhancement. --
[Issue 16123] alias member of member
https://issues.dlang.org/show_bug.cgi?id=16123 Iain Buclaw changed: What|Removed |Added Priority|P1 |P4 --
