llvm-project/clang/test/SemaCXX/namespace-alias.cpp

// RUN: clang-cc -fsyntax-only -verify %s

namespace N { };

namespace A = N;

int B; // expected-note {{previous definition is here}}
namespace B = N; // expected-error {{redefinition of 'B' as different kind of symbol}}

namespace C { } // expected-note {{previous definition is here}}
namespace C = N; // expected-error {{redefinition of 'C'}}

int i;
namespace D = i; // expected-error {{expected namespace name}}

namespace E = N::Foo; // expected-error {{expected namespace name}}

namespace F {
  namespace A { namespace B { } } // expected-note {{candidate found by name lookup is 'F::A::B'}}
  namespace B { } // expected-note {{candidate found by name lookup is 'F::B'}}
  using namespace A;
  namespace D = B; // expected-error {{reference to 'B' is ambiguous}}
}

namespace G { 
  namespace B = N;
}