Possible regression in latest? dmd with inherited inner classes

[Arafel]

Hi,

I have found the following regression with the latest dmd:

https://run.dlang.io/is/4KdP5s


```
class A {
	class I { }
}

class B : A {
	C c;

	class II : I {
		void fun() {
			c = new C();
		}
	}
}

class C { }

void main() { }
```

When tried with the latest DMD it fails with

 > onlineapp.d(10): Error: need this for c of type onlineapp.C

When I try "All dmd compilers" however I get

 > All versions: Success and no output

So I can't pinpoint the exact version, although I assume it'd be the 
latest one. ldc and ldc-beta compile it without problems.

I think this a bug because if I remove the inheritance of II : I, then 
it works without issue.

A.