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0604d13790
This can be used to inform users when a template should not be specialized. For example, this is the case for the standard type traits (except for `common_type` and `common_reference`, which have more complicated rules).
63 lines
2.6 KiB
C++
63 lines
2.6 KiB
C++
// RUN: %clang_cc1 %s -verify
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#if !__has_cpp_attribute(clang::no_specializations)
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# error
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#endif
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struct [[clang::no_specializations]] S {}; // expected-warning {{'no_specializations' attribute only applies to class templates, function templates, and variable templates}}
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template <class T, class U>
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struct [[clang::no_specializations]] is_same { // expected-note 2 {{marked 'no_specializations' here}}
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static constexpr bool value = __is_same(T, U);
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};
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template <class T>
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using alias [[clang::no_specializations]] = T; // expected-warning {{'no_specializations' attribute only applies to class templates, function templates, and variable templates}}
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template <>
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struct is_same<int, char> {}; // expected-error {{'is_same' cannot be specialized}}
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template <class>
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struct Template {};
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template <class T>
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struct is_same<Template<T>, Template <T>> {}; // expected-error {{'is_same' cannot be specialized}}
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bool test_instantiation1 = is_same<int, int>::value;
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template <class T, class U>
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[[clang::no_specializations]] inline constexpr bool is_same_v = __is_same(T, U); // expected-note 2 {{marked 'no_specializations' here}}
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template <>
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inline constexpr bool is_same_v<int, char> = false; // expected-error {{'is_same_v' cannot be specialized}}
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template <class T>
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inline constexpr bool is_same_v<Template <T>, Template <T>> = true; // expected-error {{'is_same_v' cannot be specialized}}
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bool test_instantiation2 = is_same_v<int, int>;
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template <class T>
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struct [[clang::no_specializations("specializing type traits results in undefined behaviour")]] is_trivial { // expected-note {{marked 'no_specializations' here}}
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static constexpr bool value = __is_trivial(T);
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};
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template <>
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struct is_trivial<int> {}; // expected-error {{'is_trivial' cannot be specialized: specializing type traits results in undefined behaviour}}
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template <class T>
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[[clang::no_specializations("specializing type traits results in undefined behaviour")]] inline constexpr bool is_trivial_v = __is_trivial(T); // expected-note {{marked 'no_specializations' here}}
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template <>
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inline constexpr bool is_trivial_v<int> = false; // expected-error {{'is_trivial_v' cannot be specialized: specializing type traits results in undefined behaviour}}
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template <class T>
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struct Partial {};
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template <class T>
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struct [[clang::no_specializations]] Partial<Template <T>> {}; // expected-warning {{'no_specializations' attribute only applies to class templates, function templates, and variable templates}}
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template <class T>
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[[clang::no_specializations]] void func(); // expected-note {{marked 'no_specializations' here}}
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template <> void func<int>(); // expected-error {{'func' cannot be specialized}}
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