Prevent brace initialization of AlphaNum
This was not intended to be supported, and it has resulted in calls as `absl::StrCat({...})`, which are not supported and only work coincidentally for the first 4 arguments due to `absl::StrCat` having overloads that take `absl::AlphaNum` directly for those.
The existing situation prevents modifying the implementations of such functions to alternatives that do not have such overloads for those arguments.
PiperOrigin-RevId: 599872755
Change-Id: I02c90119b2b96a922cf7e3b5d5f02affe24a272d
diff --git a/absl/strings/str_cat.h b/absl/strings/str_cat.h
index ea2c4dc..bc8ea7d 100644
--- a/absl/strings/str_cat.h
+++ b/absl/strings/str_cat.h
@@ -93,6 +93,7 @@
#include <cstddef>
#include <cstdint>
#include <cstring>
+#include <initializer_list>
#include <string>
#include <type_traits>
#include <utility>
@@ -312,6 +313,10 @@
// No bool ctor -- bools convert to an integral type.
// A bool ctor would also convert incoming pointers (bletch).
+ // Prevent brace initialization
+ template <typename T>
+ AlphaNum(std::initializer_list<T>) = delete; // NOLINT(runtime/explicit)
+
AlphaNum(int x) // NOLINT(runtime/explicit)
: piece_(digits_, static_cast<size_t>(
numbers_internal::FastIntToBuffer(x, digits_) -
