Adding type_caster_bare_interface_demo.

tests/test_type_caster_bare_interface_demo.cpp

+#include "pybind11_tests.h"
+
+namespace pybind11_tests {
+namespace type_caster_bare_interface_demo {
+
+struct mpty {};
+
+mpty        rtrn_mpty_valu() { mpty obj; return obj; }
+mpty&&      rtrn_mpty_rref() { mpty obj; return std::move(obj); }
+mpty const& rtrn_mpty_cref() { static mpty obj; return obj; }
+mpty&       rtrn_mpty_mref() { static mpty obj; return obj; }
+mpty const* rtrn_mpty_cptr() { static mpty obj; return &obj; }
+mpty*       rtrn_mpty_mptr() { static mpty obj; return &obj; }
+
+const char* pass_mpty_valu(mpty)        { return "load_valu"; }
+const char* pass_mpty_rref(mpty&&)      { return "load_rref"; }
+const char* pass_mpty_cref(mpty const&) { return "load_cref"; }
+const char* pass_mpty_mref(mpty&)       { return "load_mref"; }
+const char* pass_mpty_cptr(mpty const*) { return "load_cptr"; }
+const char* pass_mpty_mptr(mpty*)       { return "load_mptr"; }
+
+}  // namespace type_caster_bare_interface_demo
+}  // namespace pybind11_tests
+
+namespace pybind11 {
+namespace detail {
+
+using namespace pybind11_tests::type_caster_bare_interface_demo;
+
+template <>
+struct type_caster<mpty> {
+    static constexpr auto name = _<mpty>();
+
+    // static handle cast(mpty, ...)
+    // is redundant (leads to ambiguous overloads).
+
+    static handle cast(mpty&& /*src*/,
+                       return_value_policy /*policy*/,
+                       handle /*parent*/) {
+        return str("cast_rref").release();
+    }
+
+    static handle cast(mpty const& /*src*/,
+                       return_value_policy /*policy*/,
+                       handle /*parent*/) {
+        return str("cast_cref").release();
+    }
+
+    static handle cast(mpty& /*src*/,
+                       return_value_policy /*policy*/,
+                       handle /*parent*/) {
+        return str("cast_mref").release();
+    }
+
+    static handle cast(mpty const* /*src*/,
+                       return_value_policy /*policy*/,
+                       handle /*parent*/) {
+        return str("cast_cptr").release();
+    }
+
+    static handle cast(mpty* /*src*/,
+                       return_value_policy /*policy*/,
+                       handle /*parent*/) {
+        return str("cast_mptr").release();
+    }
+
+    template <typename T_>
+    using cast_op_type = conditional_t<
+        std::is_same<remove_reference_t<T_>, const mpty*>::value, const mpty*,
+        conditional_t<
+            std::is_same<remove_reference_t<T_>, mpty*>::value, mpty*,
+            conditional_t<
+                std::is_same<T_, const mpty&>::value, const mpty&,
+                conditional_t<
+                    std::is_same<T_, mpty&>::value, mpty&,
+                    conditional_t<
+                        std::is_same<T_, mpty&&>::value, mpty&&,
+                        mpty>>>>>;
+
+    operator mpty()        { return rtrn_mpty_valu(); }
+    operator mpty&&() &&   { return rtrn_mpty_rref(); }
+    operator mpty const&() { return rtrn_mpty_cref(); }
+    operator mpty&()       { return rtrn_mpty_mref(); }
+    operator mpty const*() { return rtrn_mpty_cptr(); }
+    operator mpty*()       { return rtrn_mpty_mptr(); }
+
+    bool load(handle /*src*/, bool /*convert*/) {
+      return true;
+    }
+};
+
+}  // namespace detail
+}  // namespace pybind11
+
+namespace pybind11_tests {
+namespace type_caster_bare_interface_demo {
+
+TEST_SUBMODULE(type_caster_bare_interface_demo, m) {
+  m.def("rtrn_mpty_valu", rtrn_mpty_valu);
+  m.def("rtrn_mpty_rref", rtrn_mpty_rref);
+  m.def("rtrn_mpty_cref", rtrn_mpty_cref);
+  m.def("rtrn_mpty_mref", rtrn_mpty_mref);
+  m.def("rtrn_mpty_cptr", rtrn_mpty_cptr);
+  m.def("rtrn_mpty_mptr", rtrn_mpty_mptr);
+
+  m.def("pass_mpty_valu", pass_mpty_valu);
+  m.def("pass_mpty_rref", pass_mpty_rref);
+  m.def("pass_mpty_cref", pass_mpty_cref);
+  m.def("pass_mpty_mref", pass_mpty_mref);
+  m.def("pass_mpty_cptr", pass_mpty_cptr);
+  m.def("pass_mpty_mptr", pass_mpty_mptr);
+}
+
+}  // namespace type_caster_bare_interface_demo
+}  // namespace pybind11_tests

tests/test_type_caster_bare_interface_demo.py

+# -*- coding: utf-8 -*-
+import pytest
+
+from pybind11_tests import type_caster_bare_interface_demo as m
+
+
+def test_cast():
+    assert m.rtrn_mpty_valu() == "cast_rref"
+    assert m.rtrn_mpty_rref() == "cast_rref"
+    assert m.rtrn_mpty_cref() == "cast_cref"
+    assert m.rtrn_mpty_mref() == "cast_mref"
+    assert m.rtrn_mpty_cptr() == "cast_cptr"
+    assert m.rtrn_mpty_mptr() == "cast_mptr"
+
+
+def test_load():
+    assert m.pass_mpty_valu(None) == "load_valu"
+    assert m.pass_mpty_rref(None) == "load_rref"
+    assert m.pass_mpty_cref(None) == "load_cref"
+    assert m.pass_mpty_mref(None) == "load_mref"
+    assert m.pass_mpty_cptr(None) == "load_cptr"
+    assert m.pass_mpty_mptr(None) == "load_mptr"