[c++1z] P0195R2: Support pack-expansion of using-declarations.

This change introduces UsingPackDecl as a marker for the set of UsingDecls
produced by pack expansion of a single (unresolved) using declaration. This is
not strictly necessary (we just need to be able to map from the original using
declaration to its expansions somehow), but it's useful to maintain the
invariant that each declaration reference instantiates to refer to one
declaration.

This is a re-commit of r290080 (reverted in r290092) with a fix for a
use-after-lifetime bug.

llvm-svn: 290203

1 files changed, 35 insertions, 0 deletions

diff --git a/clang/test/PCH/cxx1z-using-declaration.cpp b/clang/test/PCH/cxx1z-using-declaration.cpp
new file mode 100644
index 00000000000..a185ff17404
--- /dev/null
+++ b/clang/test/PCH/cxx1z-using-declaration.cpp
@@ -0,0 +1,35 @@
+// No PCH:
+// RUN: %clang_cc1 -pedantic -std=c++1z -include %s -verify %s
+//
+// With PCH:
+// RUN: %clang_cc1 -pedantic -std=c++1z -emit-pch %s -o %t
+// RUN: %clang_cc1 -pedantic -std=c++1z -include-pch %t -verify %s
+
+#ifndef HEADER
+#define HEADER
+
+template<typename ...T> struct A : T... {
+  using T::f ...;
+  template<typename ...U> void g(U ...u) { f(u...); }
+};
+
+struct X { void f(); };
+struct Y { void f(int); };
+struct Z { void f(int, int); };
+
+inline A<X, Y, Z> a;
+
+#else
+
+void test() {
+  a.g();
+  a.g(0);
+  a.g(0, 0);
+  // expected-error@13 {{no match}}
+  // expected-note@16 {{candidate}}
+  // expected-note@17 {{candidate}}
+  // expected-note@18 {{candidate}}
+  a.g(0, 0, 0); // expected-note {{instantiation of}}
+}
+
+#endif