[libcxx-commits] [libcxx] [libc++] Implement LWG2991: variant copy constructor missing noexcept(see below) (PR #230241)

[A. Jiang via libcxx-commits]

================
@@ -52,6 +52,16 @@ struct NTCopy {
 static_assert(!std::is_trivially_copy_constructible<NTCopy>::value, "");
 static_assert(std::is_copy_constructible<NTCopy>::value, "");
 
+struct NoThrowNTCopy {
+  constexpr NoThrowNTCopy(int v) : value(v) {}
+  NoThrowNTCopy(const NoThrowNTCopy& that) noexcept : value(that.value) {}
+  NoThrowNTCopy(NoThrowNTCopy&&) = delete;
+  int value;
+};
+
+static_assert(!std::is_trivially_copy_constructible<NoThrowNTCopy>::value, "");
+static_assert(std::is_copy_constructible<NoThrowNTCopy>::value, "");
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frederick-vs-ja wrote:

I think we should use C++17 things. It's valueless to me to keep the consistency with the existing pre-C++17-styled lines.

```suggestion
static_assert(!std::is_trivially_copy_constructible_v<NoThrowNTCopy>);
static_assert(std::is_copy_constructible_v<NoThrowNTCopy>);
```

https://github.com/llvm/llvm-project/pull/230241