[clang-tidy] Fix a false positive in unused-using-decl check

The previous matcher "hasAnyTemplateArgument(templateArgument())" only
matches the first template argument, but the check wants to iterate all
template arguments. This patch fixes this.

Also some refactorings in this patch (to make the code reusable).

llvm-svn: 370760

1 files changed, 9 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/misc-unused-using-decls.cpp b/clang-tools-extra/test/clang-tidy/misc-unused-using-decls.cpp
index eed0baeb3eb..9511160bc2f 100644
--- a/clang-tools-extra/test/clang-tidy/misc-unused-using-decls.cpp
+++ b/clang-tools-extra/test/clang-tidy/misc-unused-using-decls.cpp
@@ -31,6 +31,8 @@ class N {};
 template <int T> class P {};
 const int Constant = 0;
 
+template <typename T> class Q {};
+
 class Base {
  public:
   void f();
@@ -169,6 +171,8 @@ using n::N;
 using n::Constant;
 // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: using decl 'Constant' is unused
 
+using n::Q;
+
 // ----- Usages -----
 void f(B b);
 void g() {
@@ -202,3 +206,8 @@ template void h(n::M<N>* t);
 template <int T>
 void i(n::P<T>* t) {}
 template void i(n::P<Constant>* t);
+
+template <typename T, template <typename> class U> class Bar {};
+// We used to report Q unsued, because we only checked the first template
+// argument.
+Bar<int, Q> *bar;