Fix #13059 FP returnByReference with function call (#6736)

Author: chrchr-github

lib/checkclass.cpp

@@ -3327,8 +3327,14 @@ static const Variable* getSingleReturnVar(const Scope* scope) {
     if (!start->astOperand1() || start->str() != "return")
         return nullptr;
     const Token* tok = start->astOperand1();
-    if (tok->str() == ".")
+    if (tok->str() == ".") {
+        const Token* top = tok->astOperand1();
+        while (Token::Match(top, "[[.]"))
+            top = top->astOperand1();
+        if (!Token::Match(top, "%var%"))
+            return nullptr;
         tok = tok->astOperand2();
+    }
     return tok->variable();
 }
 

test/testclass.cpp

@@ -9083,6 +9083,23 @@ class TestClass : public TestFixture {
         ASSERT_EQUALS("[test.cpp:6]: (performance) Function 'get1()' should return member 'str' by const reference.\n"
                       "[test.cpp:9]: (performance) Function 'get2()' should return member 'strT' by const reference.\n",
                       errout_str());
+
+        checkReturnByReference("struct S { std::string str; };\n" // #13059
+                               "struct T {\n"
+                               "    S temp() const;\n"
+                               "    S s[1];\n"
+                               "};\n"
+                               "struct U {\n"
+                               "    std::string get1() const {\n"
+                               "        return t.temp().str;\n"
+                               "    }\n"
+                               "    std::string get2() const {\n"
+                               "        return t.s[0].str;\n"
+                               "    }\n"
+                               "    T t;\n"
+                               "};\n");
+        ASSERT_EQUALS("[test.cpp:10]: (performance) Function 'get2()' should return member 'str' by const reference.\n",
+                      errout_str());
     }
 };