[libcxx-commits] [libcxx] [libc++][span] P2447R4: `std::span` over an initializer list (PR #78157)

[Hristo Hristov via libcxx-commits]

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@@ -13,22 +13,36 @@
 // constexpr explicit(Extent != dynamic_extent) span(It first, size_type count);
 //  If Extent is not equal to dynamic_extent, then count shall be equal to Extent.
 //
+// constexpr explicit(extent != dynamic_extent) span(std::initializer_list<value_type> il); // Since C++26
 
 #include <span>
 #include <cstddef>
 
+#include "test_macros.h"
+
 template <class T, std::size_t extent>
 std::span<T, extent> createImplicitSpan(T* ptr, std::size_t len) {
   return {ptr, len}; // expected-error {{chosen constructor is explicit in copy-initialization}}
 }
 
-void f() {
+void test() {
   // explicit constructor necessary
   int arr[] = {1, 2, 3};
   createImplicitSpan<int, 1>(arr, 3);
 
-  std::span<int> sp = {0, 0}; // expected-error {{no matching constructor for initialization of 'std::span<int>'}}
-  std::span<int, 2> sp2 = {0, 0}; // expected-error {{no matching constructor for initialization of 'std::span<int, 2>'}}
-  std::span<const int> csp = {0, 0}; // expected-error {{no matching constructor for initialization of 'std::span<const int>'}}
-  std::span<const int, 2> csp2 = {0, 0}; // expected-error {{no matching constructor for initialization of 'std::span<const int, 2>'}}
+  // expected-error at +1 {{no matching constructor for initialization of 'std::span<int>'}}
+  std::span<int> sp = {0, 0};
+  // expected-error at +1 {{no matching constructor for initialization of 'std::span<int, 2>'}}
+  std::span<int, 2> sp2 = {0, 0};
+#if TEST_STD_VER >= 26
+  // No error in C++26
+  std::span<const int> csp = {0, 0};
+  // expected-error at +1 {{chosen constructor is explicit in copy-initialization}}
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H-G-Hristov wrote:

Thanks! I'll update the tests.

https://github.com/llvm/llvm-project/pull/78157