Re: 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;
}