gcc/testsuite/g++.dg/cpp1z/nested-namespace-def2.C - gcc - Git at Google

 // { dg-options "-std=c++11 -pedantic-errors" }

 namespace A::B::C // { dg-error "nested namespace definitions only available with" }
 {
 }
	// { dg-options "-std=c++11 -pedantic-errors" }

	namespace A::B::C // { dg-error "nested namespace definitions only available with" }
	{
	}