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44 
45 #ifndef KOKKOS_KOKKOS_WORKTAGTRAIT_HPP
46 #define KOKKOS_KOKKOS_WORKTAGTRAIT_HPP
47 
48 #include <Kokkos_Macros.hpp>
49 #include <Kokkos_Concepts.hpp>  // is_execution_space
50 #include <traits/Kokkos_PolicyTraitAdaptor.hpp>
51 #include <traits/Kokkos_Traits_fwd.hpp>
52 
53 namespace Kokkos {
54 namespace Impl {
55 
56 //==============================================================================
57 // <editor-fold desc="trait specification"> {{{1
58 
59 struct WorkTagTrait : TraitSpecificationBase<WorkTagTrait> {
60   struct base_traits {
61     using work_tag = void;
62   };
63 };
64 
65 // </editor-fold> end trait specification }}}1
66 //==============================================================================
67 
68 //==============================================================================
69 // <editor-fold desc="AnalyzeExecPolicy specializations"> {{{1
70 
71 // Since we don't have subsumption in pre-C++20, we need to have the work tag
72 // "trait" handling code be unspecialized, so we handle it instead in a class
73 // with a different name.
74 template <class... Traits>
75 struct AnalyzeExecPolicyHandleWorkTag : AnalyzeExecPolicy<void, Traits...> {
76   using base_t = AnalyzeExecPolicy<void, Traits...>;
77   using base_t::base_t;
78 };
79 
80 template <class WorkTag, class... Traits>
81 struct AnalyzeExecPolicyHandleWorkTag<WorkTag, Traits...>
82     : AnalyzeExecPolicy<void, Traits...> {
83   using base_t = AnalyzeExecPolicy<void, Traits...>;
84   using base_t::base_t;
85   static_assert(std::is_void<typename base_t::work_tag>::value,
86                 "Kokkos Error: More than one work tag given");
87   using work_tag = WorkTag;
88 };
89 
90 // This only works if this is not a partial specialization, so we have to
91 // do the partial specialization elsewhere
92 template <class Enable, class... Traits>
93 struct AnalyzeExecPolicy : AnalyzeExecPolicyHandleWorkTag<Traits...> {
94   using base_t = AnalyzeExecPolicyHandleWorkTag<Traits...>;
95   using base_t::base_t;
96 };
97 
98 // </editor-fold> end AnalyzeExecPolicy specializations }}}1
99 //==============================================================================
100 
101 //==============================================================================
102 // <editor-fold desc="PolicyTraitMatcher specializations"> {{{1
103 
104 // In order to match the work tag trait the work tag "matcher" needs to be
105 // unspecialized and the logic needs to be handled in a differently-named class,
106 // just like above.
107 template <class TraitSpec, class Trait>
108 struct PolicyTraitMatcherHandleWorkTag : std::false_type {};
109 
110 template <class Trait>
111 struct PolicyTraitMatcherHandleWorkTag<WorkTagTrait, Trait>
112     : std::integral_constant<bool, !std::is_void<Trait>::value> {};
113 
114 template <class TraitSpec, class Trait, class Enable>
115 struct PolicyTraitMatcher /* unspecialized! */
116     : PolicyTraitMatcherHandleWorkTag<TraitSpec, Trait> {};
117 
118 // </editor-fold> end PolicyTraitMatcher specializations }}}1
119 //==============================================================================
120 
121 }  // end namespace Impl
122 }  // end namespace Kokkos
123 
124 #endif  // KOKKOS_KOKKOS_WORKTAGTRAIT_HPP
125