[ASTMatchers] Add a usingDirectiveDecl matcher that was missing for some reason.

[bkramer]

Summary

This matches using namespace declarations.

[djasper]

Looks good.

[bkramer]

Closed by commit rL213152 (authored by d0k).

cfe/trunk/include/clang/ASTMatchers/ASTMatchers.h

 /// \code
 ///   namespace X { int x; }
 ///   using X::x;
 /// \endcode
 /// usingDecl()
 ///   matches \code using X::x \endcode
 const internal::VariadicDynCastAllOfMatcher<Decl, UsingDecl> usingDecl;
 
+/// \brief Matches using namespace declarations.
+///
+/// Given
+/// \code
+///   namespace X { int x; }
+///   using namespace X;
+/// \endcode
+/// usingDirectiveDecl()
+///   matches \code using namespace X \endcode
+const internal::VariadicDynCastAllOfMatcher<Decl, UsingDirectiveDecl>
+    usingDirectiveDecl;
+
 /// \brief Matches unresolved using value declarations.
 ///
 /// Given
 /// \code
 ///   template<typename X>
 ///   class C : private X {
 ///     using X::x;
 ///   };

cfe/trunk/unittests/ASTMatchers/ASTMatchersTest.cpp

TEST(UsingDeclaration, ThroughUsingDeclaration) {
   EXPECT_TRUE(matches(
       "namespace a { void f(); } using a::f; void g() { f(); }",
       declRefExpr(throughUsingDecl(anything()))));
   EXPECT_TRUE(notMatches(
       "namespace a { void f(); } using a::f; void g() { a::f(); }",
       declRefExpr(throughUsingDecl(anything()))));
 }
 
+TEST(UsingDirectiveDeclaration, MatchesUsingNamespace) {
+  EXPECT_TRUE(matches("namespace X { int x; } using namespace X;",
+                      usingDirectiveDecl()));
+  EXPECT_FALSE(
+      matches("namespace X { int x; } using X::x;", usingDirectiveDecl()));
+}
+
 TEST(SingleDecl, IsSingleDecl) {
   StatementMatcher SingleDeclStmt =
       declStmt(hasSingleDecl(varDecl(hasInitializer(anything()))));
   EXPECT_TRUE(matches("void f() {int a = 4;}", SingleDeclStmt));
   EXPECT_TRUE(notMatches("void f() {int a;}", SingleDeclStmt));
   EXPECT_TRUE(notMatches("void f() {int a = 4, b = 3;}",
                           SingleDeclStmt));
 }