C++: Guard against parent binding loop

Task-number: QTCREATORBUG-16146
Change-Id: Ib2a790954517859acd7ca5f16c7d889d28208fb0
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>

src/libs/cplusplus/LookupContext.cpp

@@ -88,10 +88,10 @@ static bool isNestedInstantiationEnclosingTemplate(
         ClassOrNamespace *nestedClassOrNamespaceInstantiation,
         ClassOrNamespace *enclosingTemplateClassInstantiation)
 {
-    QList<ClassOrNamespace *> processed;
+    QSet<ClassOrNamespace *> processed;
     while (enclosingTemplateClassInstantiation
            && !processed.contains(enclosingTemplateClassInstantiation)) {
-        processed.append(enclosingTemplateClassInstantiation);
+        processed.insert(enclosingTemplateClassInstantiation);
         if (enclosingTemplateClassInstantiation == nestedClassOrNamespaceInstantiation)
             return false;
         enclosingTemplateClassInstantiation = enclosingTemplateClassInstantiation->parent();
@@ -454,8 +454,13 @@ QList<LookupItem> LookupContext::lookup(const Name *name, Scope *scope) const
                     candidates = binding->find(name);
 
                     // try find this name in parent class
-                    while (candidates.isEmpty() && (binding = binding->parent()))
+                    QSet<ClassOrNamespace *> processed;
+                    while (candidates.isEmpty() && (binding = binding->parent())) {
+                        if (processed.contains(binding))
+                            break;
+                        processed.insert(binding);
                         candidates = binding->find(name);
+                    }
 
                     if (! candidates.isEmpty())
                         return candidates;
@@ -1143,8 +1148,13 @@ ClassOrNamespace *ClassOrNamespace::nestedType(const Name *name, ClassOrNamespac
             instantiation->_name = templId;
         instantiation->_templateId = templId;
 
-        while (!origin->_symbols.isEmpty() && origin->_symbols[0]->isBlock())
+        QSet<ClassOrNamespace *> processed;
+        while (!origin->_symbols.isEmpty() && origin->_symbols[0]->isBlock()) {
+            if (processed.contains(origin))
+                break;
+            processed.insert(origin);
             origin = origin->parent();
+        }
 
         instantiation->_instantiationOrigin = origin;
 

src/plugins/cpptools/cppcompletionassist.cpp

@@ -1513,7 +1513,12 @@ bool InternalCppCompletionAssistProcessor::globalCompletion(Scope *currentScope)
         }
     }
 
+    QSet<ClassOrNamespace *> processed;
     for (; currentBinding; currentBinding = currentBinding->parent()) {
+        if (processed.contains(currentBinding))
+            break;
+        processed.insert(currentBinding);
+
         foreach (ClassOrNamespace* u, currentBinding->usings())
             usingBindings.append(u);
 

tests/auto/cplusplus/checksymbols/tst_checksymbols.cpp

@@ -222,6 +222,7 @@ private slots:
     void test_checkForValidSymbolFileId();
 
     void test_parentOfBlock();
+    void test_infiniteLoop();
 
     void findField();
     void findField_data();
@@ -1203,6 +1204,41 @@ void tst_CheckSymbols::test_parentOfBlock()
     BaseTestCase tc(source);
 }
 
+void tst_CheckSymbols::test_infiniteLoop()
+{
+    const QByteArray source =
+        "template <class> struct TNode;\n"
+        "template <class> struct TMetaNode;\n"
+        "\n"
+        "template <class X>\n"
+        "struct TTraits {\n"
+        "   using TX        = X;\n"
+        "   using TNodeType = TNode<TX>;\n"
+        "};\n"
+        "\n"
+        "template <class X>\n"
+        "struct TMetaNode {\n"
+        "   using TTraitsType = TTraits<X>;\n"
+        "};\n"
+        "\n"
+        "template <class X>\n"
+        "void nonmember() {\n"
+        "   using TMetaNodeType = TMetaNode<X>;\n"
+        "}\n"
+        "\n"
+        "template <class X>\n"
+        "struct TNode {\n"
+        "   using TTraitsType = TTraits<X>;\n"
+        "   void member();\n"
+        "};\n"
+        "\n"
+        "template <class X>\n"
+        "void TNode<X>::member() {}\n"
+        ;
+
+    BaseTestCase tc(source);
+}
+
 void tst_CheckSymbols::test_checksymbols_infiniteLoop_data()
 {
     QTest::addColumn<QByteArray>("source1");