diff options
author | Håvard Pettersen <havardpe@oath.com> | 2020-06-13 16:23:42 +0000 |
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committer | Håvard Pettersen <havardpe@oath.com> | 2020-06-13 16:23:42 +0000 |
commit | e7c5b55b45c0dca76ab593f979c7fba471ff4c30 (patch) | |
tree | 342004e6d5c9a1e9b8ec81be3b3ddbd883a896ac /vespalib/src | |
parent | c9c54cbc1f20ed5f54bc63035fe7881604c795ff (diff) |
make type type member detection a generic trait and test it
Diffstat (limited to 'vespalib/src')
-rw-r--r-- | vespalib/src/tests/traits/traits_test.cpp | 10 | ||||
-rw-r--r-- | vespalib/src/vespa/vespalib/util/traits.h | 6 | ||||
-rw-r--r-- | vespalib/src/vespa/vespalib/util/typify.h | 24 |
3 files changed, 27 insertions, 13 deletions
diff --git a/vespalib/src/tests/traits/traits_test.cpp b/vespalib/src/tests/traits/traits_test.cpp index 0a29721df1d..7751327df75 100644 --- a/vespalib/src/tests/traits/traits_test.cpp +++ b/vespalib/src/tests/traits/traits_test.cpp @@ -42,4 +42,14 @@ TEST("require that can_skip_destruction works") { EXPECT_EQUAL(can_skip_destruction<Child2>::value, true); } +struct NoType {}; +struct TypeType { using type = NoType; }; +struct NoTypeType { static constexpr int type = 3; }; + +TEST("require that type type member can be detected") { + EXPECT_FALSE(has_type_type_v<NoType>); + EXPECT_TRUE(has_type_type_v<TypeType>); + EXPECT_FALSE(has_type_type_v<NoTypeType>); +} + TEST_MAIN() { TEST_RUN_ALL(); } diff --git a/vespalib/src/vespa/vespalib/util/traits.h b/vespalib/src/vespa/vespalib/util/traits.h index eb0385abc72..7f8945954a8 100644 --- a/vespalib/src/vespa/vespalib/util/traits.h +++ b/vespalib/src/vespa/vespalib/util/traits.h @@ -39,4 +39,10 @@ struct can_skip_destruction : std::is_trivially_destructible<T> {}; //----------------------------------------------------------------------------- +template <typename, typename = std::void_t<>> struct has_type_type : std::false_type {}; +template <typename T> struct has_type_type<T, std::void_t<typename T::type>> : std::true_type {}; +template <typename T> constexpr bool has_type_type_v = has_type_type<T>::value; + +//----------------------------------------------------------------------------- + } // namespace vespalib diff --git a/vespalib/src/vespa/vespalib/util/typify.h b/vespalib/src/vespa/vespalib/util/typify.h index afedb4219a5..0d84d1756a5 100644 --- a/vespalib/src/vespa/vespalib/util/typify.h +++ b/vespalib/src/vespa/vespalib/util/typify.h @@ -2,6 +2,7 @@ #pragma once +#include "traits.h" #include <stddef.h> #include <utility> @@ -32,8 +33,8 @@ template <typename T, T VALUE> struct TypifyResultValue { /** * Typification result for values resolving into simple templates * (templated on one type). Using this exact template is not required, - * but is supplied as convenience and example. The resolved template - * should be called 'templ' for consistency across typifiers. + * but is supplied for convenience and as example. The resolved + * template should be called 'templ' for consistency across typifiers. **/ template <template<typename> typename TT> struct TypifyResultSimpleTemplate { template <typename T> using templ = TT<T>; @@ -71,22 +72,19 @@ template <size_t N, typename Typifier, typename Target, typename ...Rs> struct T static_assert(sizeof...(Rs) == N); return Target::template invoke<Rs...>(); } - template <class, class = std::void_t<>> struct has_type : std::false_type {}; - template <class T> struct has_type<T, std::void_t<typename T::type>> : std::true_type {}; template <typename T, typename ...Args> static decltype(auto) select(T &&value, Args &&...args) { if constexpr (N == sizeof...(Rs)) { return Target::template invoke<Rs...>(std::forward<T>(value), std::forward<Args>(args)...); } else { return Typifier::resolve(value, [&](auto t)->decltype(auto) - { - using X = decltype(t); - constexpr bool x_has_type = has_type<X>::value; - if constexpr (x_has_type) { - return TypifyInvokeImpl<N, Typifier, Target, Rs..., typename X::type>::select(std::forward<Args>(args)...); - } else { - return TypifyInvokeImpl<N, Typifier, Target, Rs..., X>::select(std::forward<Args>(args)...); - } - }); + { + using X = decltype(t); + if constexpr (has_type_type_v<X>) { + return TypifyInvokeImpl<N, Typifier, Target, Rs..., typename X::type>::select(std::forward<Args>(args)...); + } else { + return TypifyInvokeImpl<N, Typifier, Target, Rs..., X>::select(std::forward<Args>(args)...); + } + }); } } }; |