This issue was solved with changeset r41267.
Eric, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.
bignum.c (integer_unpack_num_bdigits_small): Fix a comple error on
clang -Werror,-Wshorten-64-to-32
Reported by Eric Hodel. [ruby-core:55467] [Bug #8522]