Fix FP with invalidContainerRef (#2141)

lib/checkstl.cpp

@@ -839,7 +839,7 @@ void CheckStl::invalidContainer()
                     bool addressOf = false;
                     const Variable* var = getLifetimeVariable(info.tok, ep, &addressOf);
                     // Check the reference is created before the change
-                    if (var && !addressOf) {
+                    if (var && var->declarationId() == tok->varId() && !addressOf) {
                         // An argument always reaches
                         if (var->isArgument() || (!var->isReference() && !var->isRValueReference() &&
                                                   !isVariableDecl(tok) && reaches(var->nameToken(), tok, library, &ep))) {

test/teststl.cpp

@@ -3976,6 +3976,16 @@ private:
               "}\n",
               true);
         ASSERT_EQUALS("", errout.str());
+
+        check("std::vector<std::string> g();\n"
+              "void f() {\n"
+              "    std::vector<std::string> x = g();\n"
+              "    const std::string& y = x[1];\n"
+              "    std::string z;\n"
+              "    z += \"\";\n"
+              "    z += y;\n"
+              "}\n",true);
+        ASSERT_EQUALS("", errout.str());
     }
 
     void findInsert() {