[clang-tidy] Fix a template function false positive in misc-unused-using-decls check.

Summary: Ignore warning uninstantiated template function usages.

Reviewers: djasper, alexfh

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D20326

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@269906 91177308-0d34-0410-b5e6-96231b3b80d8

clang-tidy/misc/UnusedUsingDeclsCheck.cpp

@@ -10,6 +10,7 @@
 #include "UnusedUsingDeclsCheck.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchersInternal.h"
 #include "clang/Lex/Lexer.h"
 
 using namespace clang::ast_matchers;
@@ -18,12 +19,20 @@ namespace clang {
 namespace tidy {
 namespace misc {
 
+namespace {
+// FIXME: Move this node matcher to ASTMatcher.
+const internal::VariadicDynCastAllOfMatcher<Stmt, UnresolvedLookupExpr>
+    unresolvedLookupExpr;
+}
+
 void UnusedUsingDeclsCheck::registerMatchers(MatchFinder *Finder) {
   Finder->addMatcher(usingDecl(isExpansionInMainFile()).bind("using"), this);
   auto DeclMatcher = hasDeclaration(namedDecl().bind("used"));
   Finder->addMatcher(loc(recordType(DeclMatcher)), this);
   Finder->addMatcher(loc(templateSpecializationType(DeclMatcher)), this);
   Finder->addMatcher(declRefExpr().bind("used"), this);
+  Finder->addMatcher(callExpr(callee(unresolvedLookupExpr().bind("used"))),
+                     this);
 }
 
 void UnusedUsingDeclsCheck::check(const MatchFinder::MatchResult &Result) {
@@ -81,6 +90,13 @@ void UnusedUsingDeclsCheck::check(const MatchFinder::MatchResult &Result) {
       removeFromFoundDecls(VD);
     }
   }
+  // Check the uninstantiated template function usage.
+  if (const auto *ULE = Result.Nodes.getNodeAs<UnresolvedLookupExpr>("used")) {
+    for (const NamedDecl* ND : ULE->decls()) {
+      if (const auto *USD = dyn_cast<UsingShadowDecl>(ND))
+        removeFromFoundDecls(USD->getTargetDecl()->getCanonicalDecl());
+    }
+  }
 }
 
 void UnusedUsingDeclsCheck::removeFromFoundDecls(const Decl *D) {

test/clang-tidy/misc-unused-using-decls.cpp

@@ -16,6 +16,7 @@ class I {
  public:
   static int ii;
 };
+template <typename T> class J {};
 
 class Base {
  public:
@@ -29,6 +30,7 @@ int UsedFunc() { return 1; }
 int UnusedFunc() { return 1; }
 template <typename T> int UsedTemplateFunc() { return 1; }
 template <typename T> int UnusedTemplateFunc() { return 1; }
+template <typename T> int UsedInTemplateFunc() { return 1; }
 
 class ostream {
 public:
@@ -70,6 +72,13 @@ using n::UnusedFunc; // UnusedFunc
 using n::cout;
 using n::endl;
 
+using n::UsedInTemplateFunc;
+using n::J;
+template <typename T> void Callee() {
+  J<T> j;
+  UsedInTemplateFunc<T>();
+}
+
 #define DEFINE_INT(name)        \
   namespace INT {               \
   static const int _##name = 1; \