__traits(allMembers) and aliases

[Mike Parker via Digitalmars-d-learn]

On Tuesday, 25 August 2015 at 12:48:12 UTC, Dejan Lekic wrote:
> It is off-topic (sorry for that), but how you grab only those 
> (say functions) in a module that are annotated with @ChoseMe ?? 
> allMembers trait gives bunch of strings, and I could not find a 
> way to use them with hasUDA template...

Here's the actual implementation:

```
template isDerelictSymbol(alias SymbolContainer, string sym)
         {
             static if(is(typeof(hasUDA!(__traits(getMember, 
SymbolContainer, sym), DerelictSymbol)))) {
                 static if(hasUDA!(__traits(getMember, 
SymbolContainer, sym), DerelictSymbol))
                     enum isDerelictSymbol = true;
                 else
                     enum isDerelictSymbol = false;
             }
             else enum isDerelictSymbol = false;
         }
```

sym comes from allMembers. The typeof test probably isn't 
necessary in most cases, but function pointer aliases of this 
form:
```
extern(C) @nogc nothrow {
    alias FuncPtr = void funcPtr;
}
```
...fail to compile if I don't do the typeof check. If I can 
figure out a way to test for aliases, I can eliminate that bit as 
well.