Here are the minimal testcases:

Case 1:

struct A
{
	int a;
};

struct T
{
	int x;

	T() : x([]{
		sizeof(::A::a);
		return 0;
	}())
	{}
};

Case 2:

struct A
{
	int a;
};

void f()
{
	[]{sizeof(A::a);};
}

Tested at coliru.stacked-crooked.com (g++ -v shows it's a x86-64 linux host):

Case 1:
$ g++-4.8 -fsyntax-only -std=c++11 main.cpp
main.cpp: In lambda function:
main.cpp:11:15: error: type 'A' is not a base type for type 'T'
   sizeof(::A::a);
               ^
Case 2:
$ g++-4.8 -fsyntax-only -std=c++11 main.cpp
main.cpp: In lambda function:
main.cpp:10:15: internal compiler error: Segmentation fault
  []{sizeof(A::a);};
               ^

I have exactly the same errors for both cases using mingw-builds 4.8.0(i686-w64-mingw32) compiled today from sf.net on my Win7 x64 host.

From some others, I've heard Case 1 is accepted by g++-4.8 compiled just now on Ubuntu12.04, but the ICE still exists for Case 2.

G++ 4.7 accepts both cases.