utx::make_signed_t is used to get a signed integral type from a known source integral type.
That is, it gets utx::ix32 from utx::ux16, utx::ix32; gets utx::i32 from utx::u16, utx::i32; gets utx::i64 from utx::u32, utx::i64; ... etc.
If the source integral type is greater than or equal to utx::u64 or utx::ux64, it gets utx::overflow_type.
If the source type is not utx::integral type, it gets utx::overflow_type too, instead of compile errors.
utx::make_signed_t related - utx::make_signed_basic_t, utx::make_signed_uct_t
using target_type = utx::make_signed_t<source_integral_type>; static_assert(! utx::is_same_v<target_type, utx::overflow_type>);