style: clang-tidy: readability-container-size-empty

.clang-tidy

@@ -4,6 +4,7 @@ Checks: '
 -*,
 llvm-namespace-comment,
 modernize-use-override,
+readability-container-size-empty,
 '
 
 HeaderFilterRegex: 'pybind11/.*h'

include/pybind11/cast.h

@@ -59,7 +59,7 @@ public:
         Py_CLEAR(ptr);
 
         // A heuristic to reduce the stack's capacity (e.g. after long recursive calls)
-        if (stack.capacity() > 16 && stack.size() != 0 && stack.capacity() / stack.size() > 2)
+        if (stack.capacity() > 16 && !stack.empty() && stack.capacity() / stack.size() > 2)
             stack.shrink_to_fit();
     }
 
@@ -163,7 +163,7 @@ inline const std::vector<detail::type_info *> &all_type_info(PyTypeObject *type)
  */
 PYBIND11_NOINLINE inline detail::type_info* get_type_info(PyTypeObject *type) {
     auto &bases = all_type_info(type);
-    if (bases.size() == 0)
+    if (bases.empty())
         return nullptr;
     if (bases.size() > 1)
         pybind11_fail("pybind11::detail::get_type_info: type has multiple pybind11-registered bases");

include/pybind11/detail/class.h

@@ -592,7 +592,7 @@ inline PyObject* make_new_python_type(const type_record &rec) {
 
     auto &internals = get_internals();
     auto bases = tuple(rec.bases);
-    auto base = (bases.size() == 0) ? internals.instance_base
+    auto base = (bases.empty()) ? internals.instance_base
                                     : bases[0].ptr();
 
     /* Danger zone: from now (and until PyType_Ready), make sure to
@@ -616,7 +616,7 @@ inline PyObject* make_new_python_type(const type_record &rec) {
     type->tp_doc = tp_doc;
     type->tp_base = type_incref((PyTypeObject *)base);
     type->tp_basicsize = static_cast<ssize_t>(sizeof(instance));
-    if (bases.size() > 0)
+    if (!bases.empty())
         type->tp_bases = bases.release().ptr();
 
     /* Don't inherit base __init__ */

include/pybind11/pybind11.h

@@ -626,7 +626,7 @@ protected:
                 }
 
                 // 3. Check everything was consumed (unless we have a kwargs arg)
-                if (kwargs && kwargs.size() > 0 && !func.has_kwargs)
+                if (kwargs && !kwargs.empty() && !func.has_kwargs)
                     continue; // Unconsumed kwargs, but no py::kwargs argument to accept them
 
                 // 4a. If we have a py::args argument, create a new tuple with leftovers
@@ -814,7 +814,7 @@ protected:
             }
             if (kwargs_in) {
                 auto kwargs = reinterpret_borrow<dict>(kwargs_in);
-                if (kwargs.size() > 0) {
+                if (!kwargs.empty()) {
                     if (some_args) msg += "; ";
                     msg += "kwargs: ";
                     bool first = true;