Re: opDispatch compiles fine, but still fails to resolve?

[Vlad Levenfeld via Digitalmars-d-learn]

On Saturday, 9 August 2014 at 10:36:55 UTC, Artur Skawina via 
Digitalmars-d-learn wrote:
On 08/09/14 03:20, Vlad Levenfeld via Digitalmars-d-learn wrote:
More opDispatch woes. This feature keeps biting me, yet I keep 
trying to use it.

This time I'm trying to access elements of a vector GLSL-style 
(without swizzling... for now).

Here's the relevant code:

struct Vector (uint length, Element = double)
{
        ref @property component (string c)()
        {
            enum mat = q{xyzw};
            enum col = q{rgba};
            enum tex = q{uv};

            static if (mat.canFind (c))
                return components[mat.countUntil (c)];
            else static if (col.canFind (c))
                return components[col.countUntil (c)];
            else static if (tex.canFind (c))
                return components[tex.countUntil (c)];
            else static assert (0);
        }

        ref @property opDispatch (string c)()
        if (c.length == 1)
        {
            auto v = component!c;
            pragma(msg, typeof(v)); // this outputs the 
expected result
            return v; // so everything is fine, right? wrong...
        }

    Element[length] components;
}

Calling vector.component!`x` or something works fine, but 
calling vector.x fails with "Error: no property" etc.

Now, I'm used to opDispatch silently failing when it can't 
compile (very annoying btw), but in this case, I tested every 
line with a pragma (msg, __traits(compiles...)) and everything 
checks out. All expressions are verified CTFE-able. The 
compiler apparently makes it all the way through the method 
without a hitch, but then just fails symbol resolution anyway.

Is this just a bug? Does anyone have any advice on what else 
to try?

v.opDispatch!`x`;

Your opDispatch is returning a reference to a local 
stack-allocated
variable. D does not support real references; that 'auto v=...'
declaration creates a copy.

   ref @property opDispatch (string c)() { return component!c; }

[opDispatch works for every kind of symbol, there's no problem 
with
 @property]

artur

Yeah, sorry, I made that change last-minute to verify, with the 
pragma, that I was indeed getting the correct type. The problem 
must have been something else. I just made a complete oversight 
in the process of throwing everything but the kitchen sink into 
debugging it.