[clang] Add release note for int->enum conversion change.

[efriedma-quic]

This seems to be having some practical impact, so we should let people know.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Eli Friedman (efriedma-quic)

Changes

This seems to be having some practical impact, so we should let people know.

---

Full diff: https://github.com/llvm/llvm-project/pull/144407.diff

1 Files Affected:

• (modified) clang/docs/ReleaseNotes.rst (+3-1)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index b42d5f8425af6..e9455c0756bd9 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -65,8 +65,10 @@ C++ Specific Potentially Breaking Changes
   standard library already have their own bespoke builtins.
 - A workaround for libstdc++4.7 has been removed. Note that 4.8.3 remains the oldest
   supported libstdc++ version.
-
 - Added ``!nonnull/!align`` metadata to load of references for better codegen.
+- Checking for int->enum conversions in constant expressions is more strict;
+  in particular, ``const E x = (E)-1;`` is not treated as a constant if it's
+  out of range. This impacts old versions of Boost.  (#GH143034)
 
 ABI Changes in This Version
 ---------------------------

[erichkeane]

I see you've done this :) (Sorry, going through my WG21 backlog!). It would be neat if we mentioned how to FIX the boost issue/elaborated a bit on summarizing the discussion), but this is fine-as is.