[libcxx-commits] [libcxx] [libc++] Implement a type-safe iterator for optional (PR #154239)

[A. Jiang via libcxx-commits]

================
@@ -24,6 +25,31 @@ concept has_iterator_aliases = requires {
 static_assert(has_iterator_aliases<std::optional<int>>);
 static_assert(has_iterator_aliases<std::optional<const int>>);
 
+using Iter1 = std::optional<int>::iterator;
+using Iter2 = std::optional<double>::iterator;
+using Iter3 = std::optional<int>::const_iterator;
+using Iter4 = std::optional<double>::const_iterator;
+
+static_assert(std::is_convertible_v<Iter1, Iter1>);
+static_assert(!std::is_convertible_v<Iter1, Iter2>);
+static_assert(!std::is_convertible_v<Iter1, Iter3>);
+static_assert(!std::is_convertible_v<Iter1, Iter4>);
+
+static_assert(std::is_convertible_v<Iter2, Iter2>);
+static_assert(!std::is_convertible_v<Iter2, Iter1>);
+static_assert(!std::is_convertible_v<Iter2, Iter3>);
+static_assert(!std::is_convertible_v<Iter2, Iter4>);
+
+static_assert(std::is_convertible_v<Iter3, Iter3>);
+static_assert(!std::is_convertible_v<Iter3, Iter1>);
+static_assert(!std::is_convertible_v<Iter3, Iter2>);
+static_assert(!std::is_convertible_v<Iter3, Iter4>);
+
+static_assert(std::is_convertible_v<Iter4, Iter4>);
+static_assert(!std::is_convertible_v<Iter4, Iter1>);
+static_assert(!std::is_convertible_v<Iter4, Iter2>);
+static_assert(!std::is_convertible_v<Iter4, Iter3>);
+
----------------
frederick-vs-ja wrote:

I think we should add a corresponding runtime test file.

https://github.com/llvm/llvm-project/pull/154239