[llvm-branch-commits] [clang] [Clang][Backport] Demote mixed enumeration arithmetic error to a warning (#131811) (PR #139396)

[Tom Stellard via llvm-branch-commits]

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@@ -7567,9 +7567,13 @@ def warn_arith_conv_mixed_enum_types_cxx20 : Warning<
   "%sub{select_arith_conv_kind}0 "
   "different enumeration types%diff{ ($ and $)|}1,2 is deprecated">,
   InGroup<DeprecatedEnumEnumConversion>;
-def err_conv_mixed_enum_types_cxx26 : Error<
+
+def err_conv_mixed_enum_types: Error <
   "invalid %sub{select_arith_conv_kind}0 "
   "different enumeration types%diff{ ($ and $)|}1,2">;
+def warn_conv_mixed_enum_types_cxx26 : Warning <
+  err_conv_mixed_enum_types.Summary>,
+  InGroup<EnumEnumConversion>, DefaultError;
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tstellar wrote:

Unfortunately our ABI checker job doesn't really work, but I think this is an ABI break, because it's adding a new enum value.

https://github.com/llvm/llvm-project/pull/139396