Checking for manifest constants

[Bogdan]

I was using a trick with dmd to check for manifest constants 
which worked until dmd v2.094. Yesterday I tried it on the latest 
compiler and it failed with:


source/introspection/manifestConstant.d(37,28): Error: need this 
for name of type string
source/introspection/type.d(156,13): Error: value of this is not 
known at compile time

any ideas how to fix it? or, is it a bug with dmd?

```

/// Check if a member is manifest constant
bool isManifestConstant(T, string name)() {
   mixin(`return is(typeof(T.init.` ~ name ~ `)) && 
!is(typeof(&T.init.` ~ name ~ `));`);
}

/// ditto
bool isManifestConstant(alias T)() {
   return is(typeof(T)) && !is(typeof(&T));
}

enum globalConfig = 32;
int globalValue = 22;

unittest {
   struct Test {
     enum config = 3;
     int value = 2;
   }

   static assert(isManifestConstant!(Test.config));
   static assert(isManifestConstant!(Test, "config"));
   static assert(isManifestConstant!(globalConfig));

   static assert(!isManifestConstant!(Test.value));
   static assert(!isManifestConstant!(Test, "value"));
   static assert(!isManifestConstant!(globalValue));
}

void main() {}


```