[libc++] Require concepts support for <numbers>
Similar to <concepts>, we need to protect the header and test against
inclusion and being run if concepts aren't supported by the compiler.
Differential Revision: https://reviews.llvm.org/D82171
Cr-Mirrored-From: https://chromium.googlesource.com/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 98eb1457ffbbd1511a151e2b88c1af4eb3ee4808
diff --git a/include/version b/include/version
index ee78e6c..acedd03 100644
--- a/include/version
+++ b/include/version
@@ -238,7 +238,9 @@
# define __cpp_lib_is_constant_evaluated 201811L
# endif
# define __cpp_lib_list_remove_return_type 201806L
-# define __cpp_lib_math_constants 201907L
+# if defined(__cpp_concepts) && __cpp_concepts >= 201811L
+# define __cpp_lib_math_constants 201907L
+# endif
// # define __cpp_lib_ranges 201811L
# define __cpp_lib_span 202002L
// # define __cpp_lib_three_way_comparison 201711L