function overloading fail: since operators clash?

i've got large big formula bottom includes twin sure namespaces: engine application.

the engine defines vector3 category typedef another vector3 class, equivalence operators lay engine namespace, vector3 class. i total category concentration also equivalence operators concentration namespace.

when i attempted compile, separate nonetheless near-by vector3 comparisons unsuccessful since couldn't an suitable equivalence operator. i suspected i causing dispute changed equivalence operators category i added, accumulate succeeded.

// engine.h
namespace engine
{
    category vector3impl { ... };
    typedef vector3impl vector3;
    bool operator==(vector3 const &lhs, vector3 const &rhs) { ... }
}


// myfile.cpp
#include "engine.h"

namespace application
{
    category myclass { ... };
    bool operator==(myclass const &lhs, myclass const &rhs) { ... }

    vacant myfunc(...)
    {
        ( myclassa == myclassb ) { ... } // builds
    }

    vacant anotherfunc(...)
    {
        engine::vector3 a, b;
        ...
        ( == b ) { ... } // fails
    }
}

however after pondering i can't since accumulate failed. there excellent conversions vector3s category vice-versa, argument-dependent look-up should pulling equivalence user engine namespace relating it.

i've attempted reproducing bug illustration c++ digest nonetheless refuses break. there contingency something large big formula bottom causing problem, nonetheless i'm certain where start looking. something opposing beast "using engine"? anyone got any ideas?