Fix #12706 FP uselessOverride with virtual function in derived class (#6382)

Author: chrchr-github

lib/checkclass.cpp

@@ -3230,6 +3230,8 @@ static bool compareTokenRanges(const Token* start1, const Token* end1, const Tok
     const Token* tok2 = start2;
     bool isEqual = false;
     while (tok1 && tok2) {
+        if (tok1->function() != tok2->function())
+            break;
         if (tok1->str() != tok2->str())
             break;
         if (tok1->str() == "this")

test/testclass.cpp

@@ -8678,6 +8678,16 @@ class TestClass : public TestFixture {
                              "    int f() override { return MACRO; }\n"
                              "};\n");
         ASSERT_EQUALS("", errout_str());
+
+        checkUselessOverride("struct B {\n" // #12706
+                             "    virtual void f() { g(); }\n"
+                             "    void g() { std::cout << \"Base\\n\"; }\n"
+                             "};\n"
+                             "struct D : B {\n"
+                             "    void f() override { g(); }\n"
+                             "    virtual void g() { std::cout << \"Derived\\n\"; }\n"
+                             "};\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
 #define checkUnsafeClassRefMember(code) checkUnsafeClassRefMember_(code, __FILE__, __LINE__)