fix 2846 (false positive for auto_ptr check with container element)

lib/checkstl.cpp

@@ -1138,7 +1138,7 @@ void CheckStl::checkAutoPointer()
                             tok3 = tok3->next();
                         }
                         tok3 = tok3->previous()->previous();
-                        if (Token::Match(tok3, "] )"))
+                        if (Token::Match(tok3->previous(), "[ ] )"))
                         {
                             autoPointerArrayError(tok2->next());
                         }

test/teststl.cpp

@@ -1321,6 +1321,15 @@ private:
     void autoPointer()
     {
 
+	// ticket 2846
+	check("void f()\n"
+	      "{\n"
+	      "    std::vector<int*> vec;\n"
+	      "    vec.push_back(new int(3));\n"
+	      "    std::auto_ptr<int> ret(vec[0]);\n"
+	      "};\n");
+        ASSERT_EQUALS("", errout.str());
+
         // ticket 2839
         check("template <class MUTEX_TYPE>\n"
               "class Guarded\n"