Capturing __FILE__ and __LINE in a variadic templated function

[Nordlöw via Digitalmars-d-learn]

On Monday, 2 November 2015 at 09:02:28 UTC, Gary Willoughby wrote:
> On Monday, 2 November 2015 at 08:23:16 UTC, Nordlöw wrote:
>> I need `T` to be an alias in order for .stringof to work.
>
> typeof(T).stringof

No, I want the variable name from the calling scope.

This works for a single argument.

void show(alias arg, string file = __FILE__, uint line = 
__LINE__, string fun = __FUNCTION__)()
{
     import std.stdio: writeln;
     try
     {
         debug writeln(file, ":",line, ":" /* , ": in ",fun */, " 
debug: ", arg.stringof, " is ", arg);
     }
     catch (Exception) { }
}

unittest
{
     int x = 11;
     show!x;
}

Prints

dbg.d:80: debug: x is 11

My try at variadic

template show(Args...)
{
     void show(string file = __FILE__, uint line = __LINE__, 
string fun = __FUNCTION__)()
     {
         import std.stdio: write, writeln;
         try
         {
             debug write(file, ":",line, ":" /* , ": in ",fun */, 
" debug: ");
             foreach (const i, Arg; Args)
             {
                 if (i) debug write(", "); // separator
                 debug write(Arg.stringof, " is ", Arg);
             }
             debug writeln();
         }
         catch (Exception) { }
     }
}

fails with compilation error

dbg.d(83,5): Error: variable x cannot be read at compile time

Why can't I make Args a sequence of aliases?