Model NamespaceAliasDecls as having their nominated namespace as an underlying

declaration. This fixes an issue where we would reject (due to a claimed
ambiguity) a case where lookup finds multiple NamespaceAliasDecls from
different scopes that nominate the same namespace.

The C++ standard doesn't make it clear that such a case is in fact valid (which
I'm working on fixing), but there are no relevant rules that distinguish using
declarations and namespace alias declarations here, so it makes sense to treat
them the same way.

llvm-svn: 256601

1 files changed, 24 insertions, 0 deletions

diff --git a/clang/test/SemaCXX/namespace-alias.cpp b/clang/test/SemaCXX/namespace-alias.cpp
index 1cf820e3e38..2ba771ed018 100644
--- a/clang/test/SemaCXX/namespace-alias.cpp
+++ b/clang/test/SemaCXX/namespace-alias.cpp
@@ -133,3 +133,27 @@ namespace PR25731 {
     X::f();
   }
 }
+
+namespace MultipleUnambiguousLookupResults {
+  namespace A { int y; }
+  namespace B {
+    namespace X { int x; }
+    namespace Y = A;
+    namespace Z = A; // expected-note {{candidate}}
+  }
+  namespace C {
+    namespace X = B::X;
+    namespace Y = A;
+    namespace Z = X; // expected-note {{candidate}}
+  }
+  using namespace B;
+  using namespace C;
+  int x1 = X::x; // ok, unambiguous
+  int y1 = Y::y; // ok, unambiguous
+  int z1 = Z::x; // expected-error {{ambiguous}}
+
+  namespace X = C::X;
+  namespace Y = A;
+  int x2 = X::x; // ok, unambiguous
+  int y2 = Y::y; // ok, unambiguous
+}