Alias template param - Undefined Identifier

[Chris Williams]

On Tuesday, 18 March 2014 at 22:42:20 UTC, anonymous wrote:
> You can pass the variable name as a string:
> Or you can get the variable name from the alias parameter:
>
>      import std.string: format;
>      template gotoPath(alias path) {
>          enum gotoPath = format(q{
>              ...
>              fs.chdir(%s);
>          }, path.stringof);
>      }
>
> I think I've read that .stringof shouldn't be used for code
> generation, but I can't think of anything better.

Your memory seems to be correct:

http://forum.dlang.org/thread/bug-11036-3@http.d.puremagic.com/issues/

It looks like the issue is that .stringOf is something generated 
according to AST information and is thus intrinsically 
compiler-specific. The ticket it links to suggest using 
__traits(identifier, X) or 'one of the Phobos helper functions 
such as "fullyQualifiedName".'

Annoying that formatting the string is required. I think you're 
right that it's ignoring my alias parameter because I'm not using 
it. Formatting doesn't accomplish anything except to use the 
parameter. But in exchange, you have to relate your format 
arguments to the %s entries, instead of the q{} contents just 
being code.


import fs = std.file;
import std.stdio;
import std.string: format;

template gotoPath(alias path) {
     enum gotoPath = format(q{
         string currPath = fs.getcwd();
         scope (exit) fs.chdir(currPath);
         fs.chdir(%s);
     }, __traits(identifier, path));
}

void doStuff(string targetDirectory) {
     mixin(gotoPath!(targetDirectory));
     writefln("b %s", fs.getcwd());
}

void main() {
     writefln("a %s", fs.getcwd());
     doStuff("/etc");
     writefln("c %s", fs.getcwd());
}