I'm compiling the following application (2 d modules)
// file c/tool.d
module c.tool;
struct Tool
{
string name;
auto generate()
{
version (DOES_NOT_WORK)
{
import std.traits : hasMember;
if (hasMember!(Tool, name))
return `writeln("this is a ` ~ mixin ("this." ~ name ~
"()") ~ `.");`;
}
else
{
if (name == "hammer")
return `writeln("this is a ` ~ this.hammer() ~ `.");`;
}
return `writeln("unknown tool ` ~ name ~ `.");`;
}
auto hammer()
{
return "screwdriver";
}
}
string code(string input)
{
auto tool = Tool(input);
return tool.generate();
}
-----------------
// file x/app.d
class Application
{
void run()
{
import c.tool;
import std.stdio;
mixin (code("hammer"));
mixin (code("transmogrifier"));
}
}
int main(string[] args)
{
auto app = new Application();
app.run();
return 0;
}
When I compile version DOES_NOT_WORK, I get the following error:
c/tool.d(13): Error: variable name cannot be read at compile time
c/tool.d(13): while looking for match for hasMember!(Tool,
name)
However, the other version ('else' case) compiles, runs, and
outputs (as expected):
this is a screwdriver.
unknown tool transmogrifier.
What's the fundamental difference that makes the variable 'name'
readable in one version and unreadable in another? Should the
version DOES_NOT_WORK not be compilable in principle or is it
only a limitation of the current CTFE implementation in the
front-end?
Thanks.
