From b23ca879ed8f31eead0104abd90230fe7282e498 Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Fri, 21 Jan 2022 20:40:10 +0100
Subject: [PATCH] Fix #10735 FP functionConst with overloaded operator[]
 [inconclusive] (#3733)

---
 lib/checkclass.cpp | 12 ++++++++++++
 test/testclass.cpp | 16 ++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/lib/checkclass.cpp b/lib/checkclass.cpp
index e3777fdd4..300355326 100644
--- a/lib/checkclass.cpp
+++ b/lib/checkclass.cpp
@@ -2168,6 +2168,18 @@ bool CheckClass::checkConstFunc(const Scope *scope, const Function *func, bool&
                         const Variable *var = end->variable();
                         if (var && var->isStlType(stl_containers_not_const))
                             return false;
+                        const Token* assignTok = end->next()->astParent();
+                        if (assignTok && assignTok->isAssignmentOp() && assignTok->astOperand1() && assignTok->astOperand1()->variable()) {
+                            const Variable* assignVar = assignTok->astOperand1()->variable();
+                            if (assignVar->isPointer() && !assignVar->isConst() && var->typeScope()) {
+                                const auto& funcMap = var->typeScope()->functionMap;
+                                // if there is no operator that is const and returns a non-const pointer, func cannot be const
+                                if (std::none_of(funcMap.begin(), funcMap.end(), [](const std::pair<std::string, const Function*>& fm) {
+                                    return fm.second->isConst() && fm.first == "operator[]" && !Function::returnsConst(fm.second);
+                                }))
+                                    return false;
+                            }
+                        }
                     }
                     if (!jumpBackToken)
                         jumpBackToken = end->next(); // Check inside the [] brackets
diff --git a/test/testclass.cpp b/test/testclass.cpp
index 475bd5f17..addc10061 100644
--- a/test/testclass.cpp
+++ b/test/testclass.cpp
@@ -175,6 +175,7 @@ private:
         TEST_CASE(const70); // variadic template can receive more arguments than in its definition
         TEST_CASE(const71); // ticket #10146
         TEST_CASE(const72); // ticket #10520
+        TEST_CASE(const73); // ticket #10735
         TEST_CASE(const_handleDefaultParameters);
         TEST_CASE(const_passThisToMemberOfOtherClass);
         TEST_CASE(assigningPointerToPointerIsNotAConstOperation);
@@ -5886,6 +5887,21 @@ private:
         TODO_ASSERT_EQUALS("[test.cpp:7]: (style, inconclusive) Technically the member function 'C::f' can be const.\n", "", errout.str());
     }
 
+    void const73() {
+        checkConst("struct A {\n"
+                   "    int* operator[](int i);\n"
+                   "    const int* operator[](int i) const;\n"
+                   "};\n"
+                   "struct S {\n"
+                   "    A a;\n"
+                   "    void f(int j) {\n"
+                   "        int* p = a[j];\n"
+                   "        *p = 0;\n"
+                   "    }\n"
+                   "};\n");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void const_handleDefaultParameters() {
         checkConst("struct Foo {\n"
                    "    void foo1(int i, int j = 0) {\n"