getSymbolsByUDA toSymbols error instantiating

[Oleg B via Digitalmars-d-learn]

Hello. I have this code:

```d
import std.traits;

enum myuda;

class A { @myuda int x; }

class B : A
{
     @myuda int some;
     void foo() { foreach (s; getSymbolsByUDA!(typeof(this), 
myuda)) {} }
}

void main() { (new B).foo(); }
```

And have this error:

```
% rdmd uda_symbols.d
/usr/include/dmd/phobos/std/traits.d-mixin-7250(7250): Error: 
template instance AliasSeq!(some, x) AliasSeq!(some, x) is nested 
in both B and A
/usr/include/dmd/phobos/std/traits.d(7259): Error: template 
instance std.traits.getSymbolsByUDA!(B, myuda).toSymbols!("some", 
"x") error instantiating
uda_symbols.d(10):        instantiated from here: 
getSymbolsByUDA!(B, myuda)
```

If I understand correctly it's happens because code in std.traits 
can't choose between A.x and B.x, but I don't understand why. 
It's a bug or it's has a more complex base?