is(typeof(...)) vs __traits(compiles, ...)

[drug via Digitalmars-d-learn]

Currently this code does not compiles:
```
unittest
{
    class MyClass
    {
        T opCall(T)(T p)
        {
            return p;
        }
    }
    import std.container.array : Array;

    Array!MyClass arr;
}
```
but if you comment out `opCall` in MyClass this code compiles. This is 
caused by this in std.conv(4434):
```
        static if (is(typeof(chunk = T(args))))
                chunk = T(args);
```
The reason is that `is(typeof(chunk = T(args)))` returns true but does 
not compiles becase MyClass has `opCall`, compiler calls `opCall` but it 
needs `this` pointer that is unavailable. I replaced it by
```
        static if (__traits(compiles, chunk = T(args)))
                chunk = T(args);
```
it works but I'm not sure this good solution. The question is - 
shouldn't `typeof` return false in this case? if so then the right fix 
would be fix typeof.