clang-tidy readability-qualified-auto (#3702)

* Adding readability-qualified-auto to .clang-tidy

Ported from @henryiii's https://github.com/pybind/pybind11/pull/3683/commits/287527f705c8badee8ba9f6278d691fe0450ae43



* fix: support Python < 3.6
Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>

tests/test_numpy_array.cpp

@@ -89,7 +89,7 @@ template<typename... Ix> arr data_t(const arr_t& a, Ix... index) {
 }
 
 template<typename... Ix> arr& mutate_data(arr& a, Ix... index) {
-    auto ptr = (uint8_t *) a.mutable_data(index...);
+    auto *ptr = (uint8_t *) a.mutable_data(index...);
     for (py::ssize_t i = 0; i < a.nbytes() - a.offset_at(index...); i++) {
         ptr[i] = (uint8_t) (ptr[i] * 2);
     }

tests/test_numpy_dtypes.cpp

@@ -165,7 +165,7 @@ template <typename S>
 py::array_t<S, 0> create_recarray(size_t n) {
     auto arr = mkarray_via_buffer<S>(n);
     auto req = arr.request();
-    auto ptr = static_cast<S*>(req.ptr);
+    auto *ptr = static_cast<S *>(req.ptr);
     for (size_t i = 0; i < n; i++) {
         SET_TEST_VALS(ptr[i], i);
     }
@@ -175,7 +175,7 @@ py::array_t<S, 0> create_recarray(size_t n) {
 template <typename S>
 py::list print_recarray(py::array_t<S, 0> arr) {
     const auto req = arr.request();
-    const auto ptr = static_cast<S*>(req.ptr);
+    auto *const ptr = static_cast<S *>(req.ptr);
     auto l = py::list();
     for (py::ssize_t i = 0; i < req.size; i++) {
         std::stringstream ss;
@@ -192,8 +192,8 @@ py::array_t<int32_t, 0> test_array_ctors(int i) {
     std::vector<py::ssize_t> shape { 3, 2 };
     std::vector<py::ssize_t> strides { 8, 4 };
 
-    auto ptr = data.data();
-    auto vptr = (void *) ptr;
+    auto *ptr = data.data();
+    auto *vptr = (void *) ptr;
     auto dtype = py::dtype("int32");
 
     py::buffer_info buf_ndim1(vptr, 4, "i", 6);
@@ -328,7 +328,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     m.def("create_rec_nested", [](size_t n) { // test_signature
         py::array_t<NestedStruct, 0> arr = mkarray_via_buffer<NestedStruct>(n);
         auto req = arr.request();
-        auto ptr = static_cast<NestedStruct*>(req.ptr);
+        auto *ptr = static_cast<NestedStruct *>(req.ptr);
         for (size_t i = 0; i < n; i++) {
             SET_TEST_VALS(ptr[i].a, i);
             SET_TEST_VALS(ptr[i].b, i + 1);
@@ -339,7 +339,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     m.def("create_rec_partial_nested", [](size_t n) {
         py::array_t<PartialNestedStruct, 0> arr = mkarray_via_buffer<PartialNestedStruct>(n);
         auto req = arr.request();
-        auto ptr = static_cast<PartialNestedStruct*>(req.ptr);
+        auto *ptr = static_cast<PartialNestedStruct *>(req.ptr);
         for (size_t i = 0; i < n; i++) {
             SET_TEST_VALS(ptr[i].a, i);
         }
@@ -397,14 +397,14 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     m.def("test_dtype_ctors", &test_dtype_ctors);
     m.def("test_dtype_kind", [dtype_names]() {
         py::list list;
-        for (auto &dt_name : dtype_names) {
+        for (const auto &dt_name : dtype_names) {
             list.append(py::dtype(dt_name).kind());
         }
         return list;
     });
     m.def("test_dtype_char_", [dtype_names]() {
         py::list list;
-        for (auto &dt_name : dtype_names) {
+        for (const auto &dt_name : dtype_names) {
             list.append(py::dtype(dt_name).char_());
         }
         return list;
@@ -430,7 +430,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
         py::array_t<StringStruct, 0> arr = mkarray_via_buffer<StringStruct>(non_empty ? 4 : 0);
         if (non_empty) {
             auto req = arr.request();
-            auto ptr = static_cast<StringStruct*>(req.ptr);
+            auto *ptr = static_cast<StringStruct *>(req.ptr);
             for (py::ssize_t i = 0; i < req.size * req.itemsize; i++) {
                 static_cast<char *>(req.ptr)[i] = 0;
             }
@@ -450,7 +450,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     // test_array_array
     m.def("create_array_array", [](size_t n) {
         py::array_t<ArrayStruct, 0> arr = mkarray_via_buffer<ArrayStruct>(n);
-        auto ptr = (ArrayStruct *) arr.mutable_data();
+        auto *ptr = (ArrayStruct *) arr.mutable_data();
         for (size_t i = 0; i < n; i++) {
             for (size_t j = 0; j < 3; j++) {
                 for (size_t k = 0; k < 4; k++) {
@@ -476,7 +476,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     // test_enum_array
     m.def("create_enum_array", [](size_t n) {
         py::array_t<EnumStruct, 0> arr = mkarray_via_buffer<EnumStruct>(n);
-        auto ptr = (EnumStruct *) arr.mutable_data();
+        auto *ptr = (EnumStruct *) arr.mutable_data();
         for (size_t i = 0; i < n; i++) {
             ptr[i].e1 = static_cast<E1>(-1 + ((int) i % 2) * 2);
             ptr[i].e2 = static_cast<E2>(1 + (i % 2));
@@ -488,7 +488,7 @@ TEST_SUBMODULE(numpy_dtypes, m) {
     // test_complex_array
     m.def("create_complex_array", [](size_t n) {
         py::array_t<ComplexStruct, 0> arr = mkarray_via_buffer<ComplexStruct>(n);
-        auto ptr = (ComplexStruct *) arr.mutable_data();
+        auto *ptr = (ComplexStruct *) arr.mutable_data();
         for (size_t i = 0; i < n; i++) {
             ptr[i].cflt.real(float(i));
             ptr[i].cflt.imag(float(i) + 0.25f);

tests/test_pytypes.cpp

@@ -146,7 +146,7 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("return_capsule_with_name_and_destructor", []() {
         auto capsule = py::capsule((void *) 12345, "pointer type description", [](PyObject *ptr) {
             if (ptr) {
-                auto name = PyCapsule_GetName(ptr);
+                const auto *name = PyCapsule_GetName(ptr);
                 py::print("destructing capsule ({}, '{}')"_s.format(
                     (size_t) PyCapsule_GetPointer(ptr, name), name
                 ));

tests/test_smart_ptr.cpp

@@ -113,7 +113,7 @@ public:
     static void cleanupAllInstances() {
         auto tmp = std::move(myobject4_instances);
         myobject4_instances.clear();
-        for (auto o : tmp) {
+        for (auto *o : tmp) {
             delete o;
         }
     }
@@ -141,7 +141,7 @@ public:
     static void cleanupAllInstances() {
         auto tmp = std::move(myobject4a_instances);
         myobject4a_instances.clear();
-        for (auto o : tmp) {
+        for (auto *o : tmp) {
             delete o;
         }
     }

tests/test_stl_binders.cpp

@@ -41,7 +41,7 @@ public:
 };
 
 template <class Container> Container *one_to_n(int n) {
-    auto v = new Container();
+    auto *v = new Container();
     for (int i = 1; i <= n; i++) {
         v->emplace_back(i);
     }
@@ -49,7 +49,7 @@ template <class Container> Container *one_to_n(int n) {
 }
 
 template <class Map> Map *times_ten(int n) {
-    auto m = new Map();
+    auto *m = new Map();
     for (int i = 1; i <= n; i++) {
         m->emplace(int(i), E_nc(10 * i));
     }
@@ -57,7 +57,7 @@ template <class Map> Map *times_ten(int n) {
 }
 
 template <class NestMap> NestMap *times_hundred(int n) {
-    auto m = new NestMap();
+    auto *m = new NestMap();
     for (int i = 1; i <= n; i++) {
         for (int j = 1; j <= n; j++) {
             (*m)[i].emplace(int(j * 10), E_nc(100 * j));
@@ -99,16 +99,15 @@ TEST_SUBMODULE(stl_binders, m) {
     m.def("get_umnc", &times_ten<std::unordered_map<int, E_nc>>);
     // Issue #1885: binding nested std::map<X, Container<E>> with E non-copyable
     py::bind_map<std::map<int, std::vector<E_nc>>>(m, "MapVecENC");
-    m.def("get_nvnc", [](int n)
-        {
-            auto m = new std::map<int, std::vector<E_nc>>();
-            for (int i = 1; i <= n; i++) {
-                for (int j = 1; j <= n; j++) {
-                    (*m)[i].emplace_back(j);
-                }
+    m.def("get_nvnc", [](int n) {
+        auto *m = new std::map<int, std::vector<E_nc>>();
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= n; j++) {
+                (*m)[i].emplace_back(j);
             }
-            return m;
-        });
+        }
+        return m;
+    });
     py::bind_map<std::map<int, std::map<int, E_nc>>>(m, "MapMapENC");
     m.def("get_nmnc", &times_hundred<std::map<int, std::map<int, E_nc>>>);
     py::bind_map<std::unordered_map<int, std::unordered_map<int, E_nc>>>(m, "UmapUmapENC");