stringof and mixins when the types aren't available

[Adam D. Ruppe]

On Monday, 17 June 2013 at 00:27:07 UTC, David Nadlinger wrote:
> The fix is simple: Replace `mixin(T.stringof ~ ".init")` by 
> `return mixin("T.init")`.

Eh that doesn't seem to work in a more complex case... here's 
something that tries to implement an interface with stubs. The 
hard part is the arguments of the members:

====

module a;

auto magic(Interface)() {
         import std.traits;
         template passthrough(T) { alias passthrough = T; }
         string makeCode() {
                 string code = "class Class : Interface {";
                 foreach(memIdx, member; __traits(allMembers, 
Interface)) {
                         import std.conv;
                         string args;
                         foreach(idx, arg; 
ParameterTypeTuple!(__traits(getMember, Interface, member))) {
                                 if(idx) args ~= ",";
                                 //args ~= arg.stringof ~ " arg" ~ 
to!string(idx);

                                 // trying to use local names
                                 args ~= 
"passthrough!(ParameterTypeTuple!(__traits(getMember, Interface, 
\""~member~"\"))[" ~ to!string(idx) ~ "]) arg" ~ to!           
string(idx);
                         }
                         code ~= "override 
ReturnType!(__traits(getMember, Interface, \""~member~"\")) " ~ 
member ~ "(" ~ args ~ ") {}";
                 }

                 code ~= "}";
                 return code;
         }

         pragma(msg, makeCode());
         mixin(makeCode());
         return new Class();
}

=====

module b;

struct S{};
interface Test { void foo(S s); }

void main() {
    import a;
    auto s = magic!Test();
}

===


The stringof doesn't work because the name is unknown. But the 
longer one, currently uncommented, doesn't seem to work either. 
dmd just dumps a whole lot of trash errors referencing phobos and 
nothing specifically about this code... eyeballing it, I don't 
think I screwed it up though.


Is this the right principle at least?