Fix -Wconversion warnings

include/fmt/core.h

@@ -1242,7 +1242,7 @@ template <typename Context> class basic_format_args {
 
   internal::type type(int index) const {
     int shift = index * internal::packed_arg_bits;
-    int mask = (1 << internal::packed_arg_bits) - 1;
+    unsigned int mask = (1 << internal::packed_arg_bits) - 1;
     return static_cast<internal::type>((types_ >> shift) & mask);
   }
 

include/fmt/format.h

@@ -1572,7 +1572,7 @@ template <typename Range> class basic_writer {
         basic_string_view<char_type> s(&sep, sep_size);
         // Index of a decimal digit with the least significant digit having
         // index 0.
-        unsigned digit_index = 0;
+        int digit_index = 0;
         std::string::const_iterator group = groups.cbegin();
         it = format_decimal<char_type>(
             it, abs_value, size,