Fix #12162 false negative: functionConst with container member functions (#7731)

Author: chrchr-github

lib/checkclass.cpp

@@ -2596,18 +2596,18 @@ bool CheckClass::checkConstFunc(const Scope *scope, const Function *func, Member
                 if (!vt || !vt->container)
                     return false;
                 const auto yield = vt->container->getYield(end->str());
+                const Token* parent = tok1->astParent();
+                while (Token::Match(parent, "(|.|::"))
+                    parent = parent->astParent();
                 if (contains({Library::Container::Yield::START_ITERATOR, Library::Container::Yield::END_ITERATOR, Library::Container::Yield::ITERATOR}, yield)) {
-                    const Token* parent = tok1->astParent();
-                    while (Token::Match(parent, "(|.|::"))
-                        parent = parent->astParent();
                     if (parent && parent->isComparisonOp())
                         return true;
                     // TODO: use AST
                     if (parent && parent->isAssignmentOp() && tok1->tokAt(-2)->variable() && Token::Match(tok1->tokAt(-2)->variable()->typeEndToken(), "const_iterator|const_reverse_iterator"))
                         return true;
                 }
                 if ((yield == Library::Container::Yield::ITEM || yield == Library::Container::Yield::AT_INDEX) &&
-                    (lhs->isComparisonOp() || lhs->isAssignmentOp() || (lhs->str() == "(" && Token::Match(lhs->astParent(), "%cop%"))))
+                    ((parent && parent->isComparisonOp()) || lhs->isAssignmentOp() || (lhs->str() == "(" && Token::Match(lhs->astParent(), "%cop%"))))
                     return true; // assume that these functions have const overloads
                 return false;
             };

test/testclass.cpp

@@ -6822,11 +6822,20 @@ class TestClass : public TestFixture {
         ASSERT_EQUALS("[test.cpp:3:10]: (style, inconclusive) Technically the member function 'D::f' can be const. [functionConst]\n",
                       errout_str());
 
-        checkConst("struct S {\n" // #12162
+        checkConst("int g(int);\n" // #12162
+                   "struct S {\n"
                    "    bool has(int i) { return m.find(i) != m.end(); }\n"
+                   "    bool isZero(int i) { return m.at(i) == 0; }\n"
+                   "    bool isZero() { return v.front() == 0; }\n"
+                   "    void f() { g(v.front() + 1); }\n"
+                   "    void set(int i) { m.at(i) = 0; }\n"
                    "    std::map<int, int> m;\n"
+                   "    std::vector<int> v;\n"
                    "};\n");
-        ASSERT_EQUALS("[test.cpp:2:10]: (style, inconclusive) Technically the member function 'S::has' can be const. [functionConst]\n",
+        ASSERT_EQUALS("[test.cpp:3:10]: (style, inconclusive) Technically the member function 'S::has' can be const. [functionConst]\n"
+                      "[test.cpp:4:10]: (style, inconclusive) Technically the member function 'S::isZero' can be const. [functionConst]\n"
+                      "[test.cpp:5:10]: (style, inconclusive) Technically the member function 'S::isZero' can be const. [functionConst]\n"
+                      "[test.cpp:6:10]: (style, inconclusive) Technically the member function 'S::f' can be const. [functionConst]\n",
                       errout_str());
     }