Also removing `operator T()` from smart_holder_type_caster, to fix gcc...

Also removing `operator T()` from smart_holder_type_caster, to fix gcc compilation errors. The only loss is pass_rref in test_class_sh_basic.

include/pybind11/cast.h

@@ -10,6 +10,10 @@
 
 #pragma once
 
+#ifndef PYBIND11_USE_SMART_HOLDER_AS_DEFAULT
+// #define PYBIND11_USE_SMART_HOLDER_AS_DEFAULT
+#endif
+
 #include "pytypes.h"
 #include "detail/typeid.h"
 #include "detail/descr.h"
@@ -1381,6 +1385,8 @@ struct smart_holder_type_caster : smart_holder_type_caster_load<T>,
         return cast(const_cast<T const *>(src), policy, parent); // Mutbl2Const
     }
 
+    // clang-format off
+
     template <typename T_>
     using cast_op_type = conditional_t<
         std::is_same<remove_reference_t<T_>, T const *>::value,
@@ -1389,11 +1395,8 @@ struct smart_holder_type_caster : smart_holder_type_caster_load<T>,
                       T *,
                       conditional_t<std::is_same<T_, T const &>::value,
                                     T const &,
-                                    conditional_t<std::is_same<T_, T &>::value, T &, T>>>>;
-
-    // clang-format off
+                                    T &>>>;
 
-    operator T()        { return this->loaded_as_lvalue_ref(); }
     operator T const&() { return this->loaded_as_lvalue_ref(); }
     operator T&()       { return this->loaded_as_lvalue_ref(); }
     operator T const*() { return this->loaded_as_raw_ptr_unowned(); }

tests/test_class_sh_basic.cpp

@@ -26,7 +26,6 @@ atyp const* rtrn_cptr() { return new atyp{"rtrn_cptr"}; }
 atyp*       rtrn_mptr() { return new atyp{"rtrn_mptr"}; }
 
 std::string pass_valu(atyp obj)        { return "pass_valu:" + obj.mtxt; }
-std::string pass_rref(atyp&& obj)      { return "pass_rref:" + obj.mtxt; }
 std::string pass_cref(atyp const& obj) { return "pass_cref:" + obj.mtxt; }
 std::string pass_mref(atyp& obj)       { return "pass_mref:" + obj.mtxt; }
 std::string pass_cptr(atyp const* obj) { return "pass_cptr:" + obj->mtxt; }
@@ -84,7 +83,6 @@ TEST_SUBMODULE(class_sh_basic, m) {
     m.def("rtrn_mptr", rtrn_mptr);
 
     m.def("pass_valu", pass_valu);
-    m.def("pass_rref", pass_rref);
     m.def("pass_cref", pass_cref);
     m.def("pass_mref", pass_mref);
     m.def("pass_cptr", pass_cptr);

tests/test_class_sh_basic.py

@@ -39,7 +39,6 @@ def test_cast(rtrn_f, expected):
     "pass_f, mtxt, expected",
     [
         (m.pass_valu, "Valu", "pass_valu:Valu(_MvCtor)*_CpCtor"),
-        (m.pass_rref, "Rref", "pass_rref:Rref(_MvCtor)*_CpCtor"),
         (m.pass_cref, "Cref", "pass_cref:Cref(_MvCtor)*_MvCtor"),
         (m.pass_mref, "Mref", "pass_mref:Mref(_MvCtor)*_MvCtor"),
         (m.pass_cptr, "Cptr", "pass_cptr:Cptr(_MvCtor)*_MvCtor"),