Change OnlyLiteralZero to not trigger modernize-use-nullptr
PiperOrigin-RevId: 521133781
Change-Id: I1334ea683bc01ef9b1b9800d6681e29dd2a1ec55
diff --git a/absl/types/compare.h b/absl/types/compare.h
index 1a965e9..2b89b69 100644
--- a/absl/types/compare.h
+++ b/absl/types/compare.h
@@ -36,6 +36,7 @@
#include <type_traits>
#include "absl/base/attributes.h"
+#include "absl/base/macros.h"
#include "absl/meta/type_traits.h"
namespace absl {
@@ -45,14 +46,23 @@
using value_type = int8_t;
class OnlyLiteralZero {
- // A private type which cannot be named to explicitly cast to it.
- struct MatchLiteralZero;
-
public:
+#if ABSL_HAVE_ATTRIBUTE(enable_if)
+ // On clang, we can avoid triggering modernize-use-nullptr by only enabling
+ // this overload when the value is a compile time integer constant equal to 0.
+ //
+ // In c++20, this could be a static_assert in a consteval function.
+ constexpr OnlyLiteralZero(int n) // NOLINT
+ __attribute__((enable_if(n == 0, "Only literal `0` is allowed."))) {}
+#else // ABSL_HAVE_ATTRIBUTE(enable_if)
// Accept only literal zero since it can be implicitly converted to a pointer
- // type. nullptr constants will be caught by the other constructor which
- // accepts a nullptr_t.
- constexpr OnlyLiteralZero(MatchLiteralZero *) noexcept {} // NOLINT
+ // to member type. nullptr constants will be caught by the other constructor
+ // which accepts a nullptr_t.
+ //
+ // This constructor is not used for clang since it triggers
+ // modernize-use-nullptr.
+ constexpr OnlyLiteralZero(int OnlyLiteralZero::*) noexcept {} // NOLINT
+#endif
// Fails compilation when `nullptr` or integral type arguments other than
// `int` are passed. This constructor doesn't accept `int` because literal `0`
