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Make is_default_constructible work for spans.

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This commit is contained in:
Casey Carter 2017-01-28 00:08:48 -08:00 committed by Neil MacIntosh
parent f93d325495
commit 96eaf274f8
2 changed files with 20 additions and 9 deletions
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6
gsl/span
View File

@ -308,7 +308,7 @@ namespace details
constexpr extent_type() noexcept {} constexpr extent_type() noexcept {}
template <index_type Other> template <index_type Other>
constexpr extent_type(extent_type<Other> ext) constexpr extent_type(extent_type<Other> ext)
{ {
static_assert(Other == Ext || Other == dynamic_extent, static_assert(Other == Ext || Other == dynamic_extent,
"Mismatch between fixed-size extent and size of initializing data."); "Mismatch between fixed-size extent and size of initializing data.");
@ -359,6 +359,10 @@ public:
constexpr static const index_type extent = Extent; constexpr static const index_type extent = Extent;
// [span.cons], span constructors, copy, assignment, and destructor // [span.cons], span constructors, copy, assignment, and destructor
template <bool Dependent = false,
// "Dependent" is needed to make "std::enable_if_t<Dependent || Extent <= 0>" SFINAE,
// since "std::enable_if_t<Extent <= 0>" is ill-formed when Extent is greater than 0.
class = std::enable_if_t<(Dependent || Extent <= 0)>>
constexpr span() noexcept : storage_(nullptr, details::extent_type<0>()) {} constexpr span() noexcept : storage_(nullptr, details::extent_type<0>()) {}
constexpr span(std::nullptr_t) noexcept : span() {} constexpr span(std::nullptr_t) noexcept : span() {}

23
tests/span_tests.cpp
View File

@ -149,7 +149,7 @@ SUITE(span_tests)
{ {
auto workaround_macro = []() { span<int, 1> s{ nullptr, static_cast<span<int>::index_type>(0) }; }; auto workaround_macro = []() { span<int, 1> s{ nullptr, static_cast<span<int>::index_type>(0) }; };
CHECK_THROW(workaround_macro(), fail_fast); CHECK_THROW(workaround_macro(), fail_fast);
} }
{ {
@ -680,7 +680,7 @@ SUITE(span_tests)
{ {
#ifdef CONFIRM_COMPILATION_ERRORS #ifdef CONFIRM_COMPILATION_ERRORS
span<char> s{cstr}; span<char> s{cstr};
#endif #endif
span<const char> cs{cstr}; span<const char> cs{cstr};
CHECK(cs.size() == narrow_cast<std::ptrdiff_t>(cstr.size()) && CHECK(cs.size() == narrow_cast<std::ptrdiff_t>(cstr.size()) &&
cs.data() == cstr.data()); cs.data() == cstr.data());
@ -691,7 +691,7 @@ SUITE(span_tests)
auto get_temp_vector = []() -> std::vector<int> { return {}; }; auto get_temp_vector = []() -> std::vector<int> { return {}; };
auto use_span = [](span<int> s) { static_cast<void>(s); }; auto use_span = [](span<int> s) { static_cast<void>(s); };
use_span(get_temp_vector()); use_span(get_temp_vector());
#endif #endif
} }
{ {
@ -705,7 +705,7 @@ SUITE(span_tests)
auto get_temp_string = []() -> std::string { return{}; }; auto get_temp_string = []() -> std::string { return{}; };
auto use_span = [](span<char> s) { static_cast<void>(s); }; auto use_span = [](span<char> s) { static_cast<void>(s); };
use_span(get_temp_string()); use_span(get_temp_string());
#endif #endif
} }
{ {
@ -866,7 +866,7 @@ SUITE(span_tests)
span<int, 5> av = arr; span<int, 5> av = arr;
#ifdef CONFIRM_COMPILATION_ERRORS #ifdef CONFIRM_COMPILATION_ERRORS
CHECK(av.last<6>().length() == 6); CHECK(av.last<6>().length() == 6);
#endif #endif
CHECK_THROW(av.last(6).length(), fail_fast); CHECK_THROW(av.last(6).length(), fail_fast);
} }
@ -1098,7 +1098,7 @@ SUITE(span_tests)
CHECK(beyond - first == 4); CHECK(beyond - first == 4);
CHECK(first - first == 0); CHECK(first - first == 0);
CHECK(beyond - beyond == 0); CHECK(beyond - beyond == 0);
++it; ++it;
CHECK(it - first == 1); CHECK(it - first == 1);
CHECK(*it == 2); CHECK(*it == 2);
@ -1515,7 +1515,7 @@ SUITE(span_tests)
auto f = [&]() { auto f = [&]() {
span<int, 4> _s4 = {arr2, 2}; span<int, 4> _s4 = {arr2, 2};
static_cast<void>(_s4); static_cast<void>(_s4);
}; };
CHECK_THROW(f(), fail_fast); CHECK_THROW(f(), fail_fast);
} }
@ -1523,7 +1523,7 @@ SUITE(span_tests)
span<int> av = arr2; span<int> av = arr2;
auto f = [&]() { auto f = [&]() {
span<int, 4> _s4 = av; span<int, 4> _s4 = av;
static_cast<void>(_s4); static_cast<void>(_s4);
}; };
CHECK_THROW(f(), fail_fast); CHECK_THROW(f(), fail_fast);
} }
@ -1557,6 +1557,13 @@ SUITE(span_tests)
span<int> s{arr}; span<int> s{arr};
CHECK(at(s,0) == 1 && at(s,1) == 2); CHECK(at(s,0) == 1 && at(s,1) == 2);
} }
TEST(default_constructible)
{
CHECK((std::is_default_constructible<span<int>>::value));
CHECK((std::is_default_constructible<span<int, 0>>::value));
CHECK((!std::is_default_constructible<span<int, 42>>::value));
}
} }
int main(int, const char* []) { return UnitTest::RunAllTests(); } int main(int, const char* []) { return UnitTest::RunAllTests(); }