iwyu cleanup (comprehensive only for cast.h and smart_holder*.h files).

include/pybind11/detail/init.h

@@ -11,6 +11,7 @@
 #pragma once
 
 #include "class.h"
+#include "smart_holder_sfinae_hooks_only.h"
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)

include/pybind11/detail/smart_holder_type_casters.h

@@ -4,9 +4,22 @@
 
 #pragma once
 
+#include "../pytypes.h"
+#include "common.h"
+#include "descr.h"
+#include "internals.h"
 #include "smart_holder_poc.h"
 #include "smart_holder_sfinae_hooks_only.h"
 #include "type_caster_base.h"
+#include "typeid.h"
+
+#include <cstddef>
+#include <memory>
+#include <new>
+#include <string>
+#include <type_traits>
+#include <typeinfo>
+#include <utility>
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 

include/pybind11/pybind11.h

@@ -48,6 +48,7 @@
 #include "options.h"
 #include "detail/class.h"
 #include "detail/init.h"
+#include "detail/smart_holder_sfinae_hooks_only.h"
 
 #include <memory>
 #include <vector>

include/pybind11/smart_holder.h

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include "detail/common.h"
 #include "detail/smart_holder_type_casters.h"
 #include "pybind11.h"