[Issue 1900] New: Template overload sets & traits templates

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=1900

           Summary: Template overload sets & traits templates
           Product: D
           Version: 2.012
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla at digitalmars.com
        ReportedBy: wbaxter at gmail.com


I'm not sure this kind of thing is supposed to work with template overload
sets, but I hope it is supposed to, as it is a pattern I see often in C++ code.
The idea is to define some "Traits" templates that define various compile-time
aspects of a particular type.

----
module main;

import std.stdio;
import A;
import B;
import generic;

void main()
{
    AClass a;
    BClass b;

    writefln("Traits!(AClass).name: ", Traits!(AClass).name);
    writefln("Traits!(BClass).name: ", Traits!(BClass).name);
    writefln("Traits!(int).name:    ", Traits!(int).name);

}
----
module A;

class AClass
{

}

template Traits(T : AClass)
{
    enum string name = "AClass";
}

----
module B;

class BClass
{

}

string func(BClass b) {
    return "BClass";
}


template Traits(T : BClass)
{
    enum string name = "BClass";
}

----
module generic;

struct Traits(T)
{
    const string name = "any";
}

----


Right now I get:

main.d(18): template instance Traits is not a template declaration, it is a
overloadset
main.d(18): Error: undefined identifier Traits!(AClass).name

(Also note the grammar error in the message "it is a overload set".)


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