Capturing __FILE__ and __LINE in a variadic templated function

[John Colvin via Digitalmars-d-learn]

On Monday, 2 November 2015 at 09:16:09 UTC, Nordlöw wrote:
> 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?

Works for me on multiple compilers. To be precise, this worked:

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) { }
     }
}

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