[libc++] Simplify the implementation of __next_prime a bit (llvm#143512)

Author: philnik777

libcxx/src/hash.cpp

@@ -9,7 +9,6 @@
 #include <__hash_table>
 #include <algorithm>
 #include <stdexcept>
-#include <type_traits>
 
 _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wtautological-constant-out-of-range-compare")
 
@@ -52,16 +51,15 @@ const unsigned indices[] = {
 // are fewer potential primes to search, and fewer potential primes to divide
 // against.
 
-template <size_t _Sz = sizeof(size_t)>
-inline _LIBCPP_HIDE_FROM_ABI typename enable_if<_Sz == 4, void>::type __check_for_overflow(size_t N) {
-  if (N > 0xFFFFFFFB)
-    std::__throw_overflow_error("__next_prime overflow");
-}
-
-template <size_t _Sz = sizeof(size_t)>
-inline _LIBCPP_HIDE_FROM_ABI typename enable_if<_Sz == 8, void>::type __check_for_overflow(size_t N) {
-  if (N > 0xFFFFFFFFFFFFFFC5ull)
-    std::__throw_overflow_error("__next_prime overflow");
+inline void __check_for_overflow(size_t N) {
+  if constexpr (sizeof(size_t) == 4) {
+    if (N > 0xFFFFFFFB)
+      std::__throw_overflow_error("__next_prime overflow");
+  } else {
+    static_assert(sizeof(size_t) == 8);
+    if (N > 0xFFFFFFFFFFFFFFC5ull)
+      std::__throw_overflow_error("__next_prime overflow");
+  }
 }
 
 size_t __next_prime(size_t n) {