Manual fix-ups in preparation for clang-tidy readability-braces-around-statements.

Informed by experiments under PR #3698.

include/pybind11/cast.h

@@ -915,7 +915,7 @@ template <> inline void handle::cast() const { return; }
 
 template <typename T>
 detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
-    if (obj.ref_count() > 1)
+    if (obj.ref_count() > 1) {
 #if defined(NDEBUG)
         throw cast_error("Unable to cast Python instance to C++ rvalue: instance has multiple references"
             " (compile in debug mode for details)");
@@ -923,6 +923,7 @@ detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
         throw cast_error("Unable to move from Python " + (std::string) str(type::handle_of(obj)) +
                 " instance to C++ " + type_id<T>() + " instance: instance has multiple references");
 #endif
+    }
 
     // Move into a temporary and return that, because the reference may be a local value of `conv`
     T ret = std::move(detail::load_type<T>(obj).operator T&());
@@ -1192,12 +1193,15 @@ private:
     template <size_t... Is>
     bool load_impl_sequence(function_call &call, index_sequence<Is...>) {
 #ifdef __cpp_fold_expressions
-        if ((... || !std::get<Is>(argcasters).load(call.args[Is], call.args_convert[Is])))
+        if ((... || !std::get<Is>(argcasters).load(call.args[Is], call.args_convert[Is]))) {
             return false;
+        }
 #else
-        for (bool r : {std::get<Is>(argcasters).load(call.args[Is], call.args_convert[Is])...})
+        for (bool r : {std::get<Is>(argcasters).load(call.args[Is], call.args_convert[Is])...}) {
-            if (!r)
+            if (!r) {
                 return false;
+            }
+        }
 #endif
         return true;
     }
@@ -1286,13 +1290,13 @@ private:
     }
 
     void process(list &/*args_list*/, arg_v a) {
-        if (!a.name)
+        if (!a.name) {
 #if defined(NDEBUG)
             nameless_argument_error();
 #else
             nameless_argument_error(a.type);
 #endif
-
+        }
         if (m_kwargs.contains(a.name)) {
 #if defined(NDEBUG)
             multiple_values_error();

include/pybind11/detail/init.h

@@ -276,12 +276,13 @@ struct factory<CFunc, AFunc, CReturn(CArgs...), AReturn(AArgs...)> {
         cl.def("__init__", [class_func, alias_func]
         #endif
         (value_and_holder &v_h, CArgs... args) {
-            if (Py_TYPE(v_h.inst) == v_h.type->type)
+            if (Py_TYPE(v_h.inst) == v_h.type->type) {
                 // If the instance type equals the registered type we don't have inheritance, so
                 // don't need the alias and can construct using the class function:
                 construct<Class>(v_h, class_func(std::forward<CArgs>(args)...), false);
-            else
+            } else {
                 construct<Class>(v_h, alias_func(std::forward<CArgs>(args)...), true);
+            }
         }, is_new_style_constructor(), extra...);
     }
 };

include/pybind11/detail/type_caster_base.h

@@ -625,12 +625,15 @@ public:
                 vptr = type->operator_new(type->type_size);
             } else {
                 #if defined(__cpp_aligned_new) && (!defined(_MSC_VER) || _MSC_VER >= 1912)
-                    if (type->type_align > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
+                    if (type->type_align > __STDCPP_DEFAULT_NEW_ALIGNMENT__) {
                         vptr = ::operator new(type->type_size,
                                               std::align_val_t(type->type_align));
-                    else
+                    } else {
+                        vptr = ::operator new(type->type_size);
+                    }
+                #else
+                    vptr = ::operator new(type->type_size);
                 #endif
-                vptr = ::operator new(type->type_size);
             }
         }
         value = vptr;
@@ -778,8 +781,9 @@ public:
     // with .second = nullptr.  (p.first = nullptr is not an error: it becomes None).
     PYBIND11_NOINLINE static std::pair<const void *, const type_info *> src_and_type(
             const void *src, const std::type_info &cast_type, const std::type_info *rtti_type = nullptr) {
-        if (auto *tpi = get_type_info(cast_type))
+        if (auto *tpi = get_type_info(cast_type)) {
             return {src, const_cast<const type_info *>(tpi)};
+        }
 
         // Not found, set error:
         std::string tname = rtti_type ? rtti_type->name() : cast_type.name();
@@ -928,8 +932,9 @@ public:
             // except via a user-provided specialization of polymorphic_type_hook,
             // and the user has promised that no this-pointer adjustment is
             // required in that case, so it's OK to use static_cast.
-            if (const auto *tpi = get_type_info(*instance_type))
+            if (const auto *tpi = get_type_info(*instance_type)) {
                 return {vsrc, tpi};
+            }
         }
         // Otherwise we have either a nullptr, an `itype` pointer, or an unknown derived pointer, so
         // don't do a cast

include/pybind11/pybind11.h

@@ -183,12 +183,13 @@ protected:
 #endif
             // UB without std::launder, but without breaking ABI and/or
             // a significant refactoring it's "impossible" to solve.
-            if (!std::is_trivially_destructible<capture>::value)
+            if (!std::is_trivially_destructible<capture>::value) {
                 rec->free_data = [](function_record *r) {
                     auto data = PYBIND11_STD_LAUNDER((capture *) &r->data);
                     (void) data;
                     data->~capture();
                 };
+            }
 #if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
 #  pragma GCC diagnostic pop
 #endif