Fix #12725 oppositeInnerCondition with negated bool (#6401)

Author: chrchr-github

lib/checkcondition.cpp

@@ -716,7 +716,7 @@ void CheckCondition::multiCondition2()
 
                     // Condition..
                     const Token *cond2 = tok->str() == "if" ? condStartToken->astOperand2() : condStartToken->astOperand1();
-                    const bool isReturnVar = (tok->str() == "return" && !Token::Match(cond2, "%cop%"));
+                    const bool isReturnVar = (tok->str() == "return" && (!Token::Match(cond2, "%cop%") || (cond2 && cond2->isUnaryOp("!"))));
 
                     ErrorPath errorPath;
 

test/testcondition.cpp

@@ -2129,6 +2129,15 @@ class TestCondition : public TestFixture {
               "    bool m_value = false;\n"
               "};");
         ASSERT_EQUALS("", errout_str());
+
+        // #12725
+        check("bool f(bool b) {\n"
+              "    if (b)\n"
+              "        return !b;\n"
+              "    b = g();\n"
+              "    return b;\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:3]: (style) Return value '!b' is always false\n", errout_str());
     }
 
     void oppositeInnerConditionPointers() {