http://d.puremagic.com/issues/show_bug.cgi?id=3744

           Summary: __traits getMember error in checking of second
                    argument
           Product: D
           Version: 2.040
          Platform: x86_64
        OS/Version: Linux
            Status: NEW
          Severity: blocker
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: denis.tomilin@gmail.com


--- Comment #0 from iorlas <denis.tomilin@gmail.com> 2010-01-26 15:50:48 PST ---
Created an attachment (id=557)
Example code

I've trying to get text representation of class, that can be changed in
development time.
For this problem i've used __traits functions "allModules",
"isVirtualFunction"(for filtering) and "getMember" for getting a type by member
name(from "allModules").
But i've stuck in "getMember".

>Error: string expected as second argument of __traits getMember instead of m
(see code in attachment)
in
>if (!__traits(isVirtualFunction, __traits(getMember, Check, m))){
As said in references:
>Takes two arguments, the second must be a string.

Ofc, m is normal string. I've tried to use "writeln(typeid(typeof(m)));" for
determinating a type of m-variable.
>immutable(char)[]
as printed in console. That means all ok.
But __traits still throws error.

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--- Comment #1 from iorlas <denis.tomilin@gmail.com> 2010-01-27 00:14:04 PST ---
I've tried to fix this problem and I've found this part of code, what can say about this problem:
>Object *o = (Object *)args->data[0];
>Expression *e = isExpression((Object *)args->data[1]);
>if (!e)
>{   error("expression expected as second argument of __traits %s", ident->toChars());
>    goto Lfalse;
>}
>e = e->optimize(WANTvalue | WANTinterpret);
>if (e->op != TOKstring)
>{   error("string expected as second argument of __traits %s instead of %s = %d", ident->toChars(), e->toChars(), e->op);
>    goto Lfalse;
>}
(traits.c)
Problem in this code. This code want to see const string expression(every const
string in the code). Program fails in this string:
>if (e->op != TOKstring)
Cuz e->op == TOKvar.

As i think, need to get an string from var and send it into StringExp instance
for next operations, but i donts know how.
Now i trying to find similar code in other sources.

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug@yahoo.com.au


--- Comment #2 from Don <clugdbug@yahoo.com.au> 2010-01-27 00:53:18 PST ---
(In reply to comment #1)
> I've tried to fix this problem and I've found this part of code, what can say about this problem:
> >e = e->optimize(WANTvalue | WANTinterpret);
> >if (e->op != TOKstring)
> (traits.c)

> Problem in this code. This code want to see const string expression(every const string in the code). Program fails in this string:
> >if (e->op != TOKstring)
> Cuz e->op == TOKvar.
> 
> As i think, need to get an string from var and send it into StringExp instance for next operations, but i donts know how.

e->optimize(WANTvalue|WANTinterpret) should have turned it into a TOKstring. If it's still a TOKvar, then the problem is in e->optimize or earlier.

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--- Comment #3 from iorlas <denis.tomilin@gmail.com> 2010-01-27 01:41:07 PST ---
(In reply to comment #2)
> e->optimize(WANTvalue|WANTinterpret) should have turned it into a TOKstring. If it's still a TOKvar, then the problem is in e->optimize or earlier.
Hm. Huh, why Walter don't wrote a comments for sly functions like this...
interesting, I dunno how can miss word "WANT" in "WANTvalue", but I did it +_+.
Ok, good logic, but i cant find an implementation of this function.
It must be predefined in expressions.h. And i found this:
>struct VarExp : SymbolExp{
> ...
> Expression *optimize(int result);
> ...
>}
Aha!
But implementation there's in another file - optimize.c:
>Expression *VarExp::optimize(int result)
>{
>    return fromConstInitializer(result, this);
>}
Yeah, good.

This func found in this file:
>Expression *fromConstInitializer(int result, Expression *e1)
Only this part interesting for me, cuz it returns 0, that means returns original  argument("this", with TOKvar):
>e = expandVar(result, v);

Next...
>Expression *expandVar(int result, VarDeclaration *v)
>if (v->isConst() || v->isImmutable() || v->storage_class & STCmanifest)
Yeah! It fails ;_;
But, stop! WTF? This function dont checks a WANTvalue flag and... i dunno.
I want to cry.. really. I want to solve this problem cuz its blocked my work.

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--- Comment #4 from Don <clugdbug@yahoo.com.au> 2010-01-27 02:20:05 PST ---
Just had a look at your test code.
The problem lies here:

    foreach(string m; a){
        __traits(getMember, Check, m)
    }
m is not a compile-time constant. Of course it _should_ be, but it's not.

One thing you could try in traits.c is to replace:
e = e->optimize(WANTvalue);
with  e = e->interpret(NULL);
and that'll probably get it working.

But the real problem is in tuple foreach: the iteration variable should be a compile-time constant.

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--- Comment #5 from iorlas <denis.tomilin@gmail.com> 2010-01-27 03:05:12 PST ---
(In reply to comment #4)
> Just had a look at your test code.
> The problem lies here:
> 
>     foreach(string m; a){
>         __traits(getMember, Check, m)
>     }
> m is not a compile-time constant. Of course it _should_ be, but it's not.
Yeah, i understand this, but i think this function(has/getMember and some other) useless if it can't be used in runtime.

> One thing you could try in traits.c is to replace:
> e = e->optimize(WANTvalue);
> with  e = e->interpret(NULL);
> and that'll probably get it working.
With this fix compiles ok, but if i want to get string representation of type
from variable(typeid(typeof(__traits(getMember, Check, m)))), i've get always
one string: fail.Check(). But if i try ti get this from Check.a, i've get a
"int". I dunno why, cuz i think this is bad fix.

> But the real problem is in tuple foreach: the iteration variable should be a compile-time constant.
This is problem why it doesn't compiles, ofc. But i need a functionality rather then perfectly compiles "hello world", lol.

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--- Comment #6 from Don <clugdbug@yahoo.com.au> 2010-01-28 11:09:25 PST ---
Actually, there's nothing at all wrong with __traits(getMember).
Really, you are asking for static foreach: given a compile-time constant array,
iterate over each of its members.
Since static foreach is unfortunately not going to happen (it was on Andrei's
list, but Walter rejected it), the other possibilities are to make
__traits(allMembers) into a tuple, or to use the static foreach workaround:

Something like:

enum a = __traits(allMembers, ...)'
foreach(T, int indx; ForEachTuple!(a.length))
{
   a = __traits(getMember, a[indx]);
}

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--- Comment #7 from iorlas <denis.tomilin@gmail.com> 2010-01-28 21:35:03 PST ---
(In reply to comment #6)
> Actually, there's nothing at all wrong with __traits(getMember).
> Really, you are asking for static foreach: given a compile-time constant array,
> iterate over each of its members.
> Since static foreach is unfortunately not going to happen (it was on Andrei's
> list, but Walter rejected it), the other possibilities are to make
> __traits(allMembers) into a tuple, or to use the static foreach workaround:
> 
> Something like:
> 
> enum a = __traits(allMembers, ...)'
> foreach(T, int indx; ForEachTuple!(a.length))
> {
>    a = __traits(getMember, a[indx]);
> }

Ok, good idea. But i cannot find a "ForEachTuple" template. Static version of
foreach might be help in this sitiation, but i dunno how to do it. Cuz if i use
normal foreach with this hack(using enum and index for getting a name of
member) a have one same error:
Error: string expected as second argument of __traits getMember instead of
a[indx]. =/

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--- Comment #8 from iorlas <denis.tomilin@gmail.com> 2010-02-02 14:40:11 PST ---
Maybe not a pure, but works(also, thx to eldar, qtd-developer):

template Alias(T...){ //small hack, cuz directly alias dont want to work
    alias T Alias;
}
alias Alias!(__traits(allMembers, abc)) ABCMEMBS; //alias creates data as
compile-time var
void main(){
    foreach(m;ABCMEMBS){ //now we can use it in compile-time
        writeln(m, ": ", typeid(typeof(__traits(getMember, abc, m)))); //all
ok, cuz it's in compile-time
    }
}

class abc{
    void foo(){
    }
    int a,b,c;
}

We have this output:
foo: void()
a: int
b: int
c: int

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iorlas <denis.tomilin@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P2                          |P4
            Version|2.040                       |2.041
           Severity|blocker                     |minor


--- Comment #9 from iorlas <denis.tomilin@gmail.com> 2010-02-02 14:43:13 PST ---
Changed priority, cuz now i can use one way to solve my problem. See code in prev msg.

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