Fix set_value template deduction for smart string types#633
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The set_value_type<> specializations for std::wstring, BSTR, unique_bstr, shared_bstr, unique_cotaskmem_string, and shared_cotaskmem_string incorrectly used const-qualified template parameters (e.g. set_value_type<const std::wstring>). Since reg_view_t::set_value deduces R from 'const R& value', the template parameter R is always the non-const type. This caused a static_assert failure when calling set_value with any of these types. Remove the const qualifier from all six affected specializations so the deduced type matches the specialization. Fixes microsoft#624
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Per review feedback, convert the set_value_type function family into a set_value_type_t<T> trait struct with a constexpr DWORD value member, and make set_value_type<T>() a thin wrapper that applies wistd::remove_cv_t. This removes the need for callers to strip cv-qualifiers from the deduced type while keeping the type fully specializable for future use. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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set_value_type<>specializations forstd::wstring,BSTR,unique_bstr,shared_bstr,unique_cotaskmem_string, andshared_cotaskmem_stringincorrectly used const-qualified template parameters (e.g.set_value_type<const std::wstring>).Since
reg_view_t::set_valuededucesRfromconst R& value, the template parameterRis always the non-const type. This caused astatic_assertfailure (Unsupported type for set_value_type) when callingset_valuewith any of these types:\\cpp
std::wstring value{L"Hello"};
wil::reg::set_value(hkey, L"MyValue", value); // static_assert failure
\\
The fix removes the
constqualifier from all six affected specializations so the deduced type matches.Tests added for
std::wstringlvalues (non-const, const, and empty) with both opened-key and string-key overloads.Fixes #624