How to get BaseEnumType?

[drug via Digitalmars-d-learn]

Hello
I need to get the type to which I can cast the enum for using with 
foreign library. For example:
```
enum Foo { A = "a", B = "b", }
enum Bar { A = 123, B = 432, }

static assert(is(BaseEnumType!Foo == string));
static assert(is(BaseEnumType!Bar == int));

I guess there is simple answer somewhere but I failed to find it yet.