CppEditor: Fix following signals/slots in old-style connects

... if the first argument is a call to a function returning a pointer to
QObject.

Fixes: QTCREATORBUG-13265
Change-Id: I12c2d07331a0c6dca56ad55c518240fd74be3dca
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/libs/cplusplus/ResolveExpression.cpp

@@ -1085,7 +1085,12 @@ ClassOrNamespace *ResolveExpression::baseExpression(const QList<LookupItem> &bas
             qDebug() << "-  after typedef resolving:" << oo(ty);
 
         if (accessOp == T_ARROW) {
-            if (PointerType *ptrTy = ty->asPointerType()) {
+            PointerType *ptrTy = ty->asPointerType();
+            if (!ptrTy) {
+                if (Function * const func = ty->asFunctionType())
+                    ptrTy = func->returnType()->asPointerType();
+            }
+            if (ptrTy) {
                 FullySpecifiedType type = ptrTy->elementType();
                 if (ClassOrNamespace *binding
                         = findClassForTemplateParameterInExpressionScope(r.binding(),

src/plugins/cppeditor/cppeditorplugin.h

@@ -85,6 +85,7 @@ private slots:
 
     void test_FollowSymbolUnderCursor_QObject_connect_data();
     void test_FollowSymbolUnderCursor_QObject_connect();
+    void test_FollowSymbolUnderCursor_QObject_oldStyleConnect();
 
     void test_FollowSymbolUnderCursor_classOperator_onOperatorToken_data();
     void test_FollowSymbolUnderCursor_classOperator_onOperatorToken();

src/plugins/cppeditor/followsymbol_switchmethoddecldef_test.cpp

@@ -1309,6 +1309,26 @@ void CppEditorPlugin::test_FollowSymbolUnderCursor_QObject_connect()
     F2TestCase(F2TestCase::FollowSymbolUnderCursorAction, singleDocument(source));
 }
 
+void CppEditorPlugin::test_FollowSymbolUnderCursor_QObject_oldStyleConnect()
+{
+    const QByteArray source =
+            "class O : public QObject {\n"
+            "    Q_OBJECT\n"
+            "signals:\n"
+            "    void $theSignal();\n"
+            "};\n"
+            "struct S {\n"
+            "    O* o();\n"
+            "};\n"
+            "int main()\n"
+            "{\n"
+            "    S s;\n"
+            "    QObject::connect(s.o(), SIGNAL(@theSignal()), s.o(), SIGNAL(theSignal()));\n"
+            "}\n";
+
+    F2TestCase(F2TestCase::FollowSymbolUnderCursorAction, singleDocument(source));
+}
+
 void CppEditorPlugin::test_FollowSymbolUnderCursor_classOperator_onOperatorToken_data()
 {
     QTest::addColumn<bool>("toDeclaration");