It is unreachable because we test that the cxx_stdlib_under_test is in the supported set of libraries elsewhere. Furthermore, this code relied on the `use_stdlib_type`, which is never defined. git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@348867 91177308-0d34-0410-b5e6-96231b3b80d8