Add non-template ref-to-value converting constructor to __basic_any#8320
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bdice wants to merge 3 commits intoNVIDIA:mainfrom
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Add non-template ref-to-value converting constructor to __basic_any#8320bdice wants to merge 3 commits intoNVIDIA:mainfrom
bdice wants to merge 3 commits intoNVIDIA:mainfrom
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The __basic_any value specialization inherits converting constructors from templates that accept __basic_any<_OtherInterface>. When a proxy type wraps a __basic_any reference type (e.g. __basic_any<I&>) and provides operator __basic_any<I&>&(), these template constructors cannot match: template argument deduction deduces the proxy type, not the underlying __basic_any, and implicit user-defined conversions are not considered during deduction. Add a non-template constructor __basic_any(__basic_any<_Interface&> const&) for the ref-to-value conversion case. Non-template parameters participate in implicit conversion sequences, allowing proxy types to convert through their user-defined conversion operator. This fixes any_resource construction from proxy-wrapped resource_ref and any_synchronous_resource from proxy-wrapped synchronous_resource_ref without requiring per-type overloads. Fixes NVIDIA#8316
…d refs Add regression tests for NVIDIA#8316 verifying that any_resource and any_synchronous_resource can be constructed from a value_proxy<T> that wraps resource_ref or synchronous_resource_ref via operator T&(), mimicking Cython's __Pyx_FakeReference proxy pattern.
ericniebler
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Apr 7, 2026
libcudacxx/include/cuda/__utility/__basic_any/basic_any_value.h
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Co-authored-by: Eric Niebler <eniebler@boost.org>
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miscco
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| //! @brief Non-template converting constructor from the corresponding | ||
| //! reference type `__basic_any<_Interface&>`. This enables implicit | ||
| //! conversion from proxy types (e.g. Cython's __Pyx_FakeReference) | ||
| //! that wrap a `__basic_any<_Interface&>` and provide | ||
| //! `operator __basic_any<_Interface&>&()`, since non-template parameters | ||
| //! participate in implicit conversion sequences. | ||
| _CCCL_API __basic_any(__basic_any<_Interface&> const& __other) | ||
| { | ||
| __convert_from(__other); | ||
| } |
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Thanks for the fix, please also add the corresponding move constructor and test for rvalue proxy
bdice
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Apr 9, 2026
Work around CCCL issue where any_resource cannot be constructed from Cython's __Pyx_FakeReference proxy type wrapping resource_ref. Declare any_resource and device_accessible in .pxd, add inline make_any_device_resource helper. Update all 12 constructor call sites in .pyx to use the helper. Ref: NVIDIA/cccl#8320
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Description
closes #8316
Add a non-template converting constructor
__basic_any(__basic_any<_Interface&> const&)to the__basic_anyvalue specialization, enabling implicit conversion from proxy types that wrap a__basic_anyreference type.The
__basic_anyvalue specialization provides a forwarding constructor__basic_any(_Tp&&)and template converting constructors__basic_any(__basic_any<_OtherInterface> const&). When a proxy type wraps a__basic_any<I&>(e.g. aresource_ref) and providesoperator __basic_any<I&>&(), neither path works: the forwarding constructor deduces the proxy type which doesn't satisfy the interface, and the template converting constructors can't deduce_OtherInterfacefrom the proxy since implicit user-defined conversions are not considered during template argument deduction.This occurs concretely with Cython's
__Pyx_FakeReference<T>, which wraps intermediate C++ expression results and providesoperator T&(). Constructingany_resource<P...>from a Cython-wrappedresource_ref<P...>fails at compile time.The fix adds a non-template constructor for the same-interface ref-to-value conversion. Because the parameter is non-template, the compiler considers implicit conversion sequences through the proxy's
operator T&(). The existing template converting constructor gains an additional!same_as<_OtherInterface, _Interface&>constraint to avoid ambiguity.This single fix in
__basic_anycovers all downstream types:any_resource,any_synchronous_resource, and any future__basic_any-based value types.Testing: A new test was added based on the minimal reproducer in the issue. RMM Cython bindings build and pass tests using direct
any_resourceconstruction fromresource_refwithout workaround helpers.Checklist