Ensure virtual-near-miss does not crash on functions without names

[aaron.ballman]

Summary

Special member functions don't always have names, and so calling FunctionDecl::getName() can cause assertions. This patch addresses the issue by assuming any such function needs to have the rest of its signature checked, regardless of the function name. The test case was pulled from MSVC's STL headers, where this check is causing failed assertions.

[aaron.ballman]

Now checking that both the base *and* the derived functions have names.

[alexfh]

Should be fixed in http://reviews.llvm.org/D16179.

[aaron.ballman]

You are correct, this was fixed with http://reviews.llvm.org/D16179. Thanks!

clang-tidy/misc/VirtualNearMissCheck.cpp

         if (isOverriddenByDerivedClass(BaseMD, DerivedRD))
           continue;
 
+        // If the function has an identifier for a name, then use that
+        // identifier to determine the edit distance. If the function is a
+        // special member function without an identifier, assume the edit
+        // distance is nonzero to determine whether the signature is a near
+        // miss or not.
         unsigned EditDistance =
-            BaseMD->getName().edit_distance(DerivedMD->getName());
+            (BaseMD->getDeclName().isIdentifier() &&
+             DerivedMD->getDeclName().isIdentifier())
+                ? BaseMD->getName().edit_distance(DerivedMD->getName())
+                : 1;
         if (EditDistance > 0 && EditDistance <= EditDistanceThreshold) {
           if (checkOverrideWithoutName(Context, BaseMD, DerivedMD)) {
             // A "virtual near miss" is found.

test/clang-tidy/misc-virtual-near-miss.cpp

 private:
   void funk(); // Should not warn: access qualifers don't match.
 };
+
+namespace {
+// Ensure this code does not crash due to special member functions.
+class  _Facet_base {
+public:
+  virtual ~_Facet_base() noexcept {}
+};
+
+class facet : public _Facet_base {
+protected:
+  virtual ~facet() noexcept {}
+
+public:
+  facet(const facet&) = delete;
+  facet& operator=(const facet&) = delete;
+};
+}