[clang] [Clang] Consider preferred_type in bitfield warnings (#116760) (PR #116785)

[Aaron Ballman via cfe-commits]

================
@@ -6517,8 +6517,22 @@ def warn_signed_bitfield_enum_conversion : Warning<
   "signed bit-field %0 needs an extra bit to represent the largest positive "
   "enumerators of %1">,
   InGroup<BitFieldEnumConversion>, DefaultIgnore;
+def warn_preferred_type_bitfield_too_small_for_enum : Warning<
+  "bit-field %0 is not wide enough to store all enumerators of preferred type %1">,
+  InGroup<PreferredTypeBitFieldEnumConversion>, DefaultError;
+def warn_preferred_type_unsigned_bitfield_assigned_signed_enum : Warning<
+  "assigning value of preferred signed enum type %1 to unsigned bit-field %0; "
+  "negative enumerators of enum %1 will be converted to positive values">,
+  InGroup<PreferredTypeBitFieldEnumConversion>, DefaultIgnore;
----------------
AaronBallman wrote:

I still think use of the attribute should mean this can be on by default rather than ignored by default. WDYT?

https://github.com/llvm/llvm-project/pull/116785