🎨 Don't throw away argument to smallest_uint

Problem:
- `smallest_uint` returns zero rather than the template argument it is passed.

Solution:
- Return the argument passed.

Author: elbeno

docs/bit.adoc

@@ -125,8 +125,8 @@ integral type that will fit a compile-time value.
 
 [source,cpp]
 ----
-constexpr auto x = stdx::smallest_uint<42>();   // std::uint8_t{}
-constexpr auto y = stdx::smallest_uint<1337>(); // std::uint16_t{}
+constexpr auto x = stdx::smallest_uint<42>();   // std::uint8_t{42}
+constexpr auto y = stdx::smallest_uint<1337>(); // std::uint16_t{1337}
 
 // smallest_uint_t is the type of a call to smallest_uint
 using T = stdx::smallest_uint_t<1337>; // std::uint16_t

include/stdx/bit.hpp

@@ -421,13 +421,13 @@ template <typename T> constexpr auto bit_size() -> std::size_t {
 
 template <std::size_t N> CONSTEVAL auto smallest_uint() {
     if constexpr (N <= std::numeric_limits<std::uint8_t>::digits) {
-        return std::uint8_t{};
+        return std::uint8_t{N};
     } else if constexpr (N <= std::numeric_limits<std::uint16_t>::digits) {
-        return std::uint16_t{};
+        return std::uint16_t{N};
     } else if constexpr (N <= std::numeric_limits<std::uint32_t>::digits) {
-        return std::uint32_t{};
+        return std::uint32_t{N};
     } else {
-        return std::uint64_t{};
+        return std::uint64_t{N};
     }
 }