[clang] 0cb2fe5 - [Clang] Deprecate __is_referenceable (#123185)

[via cfe-commits]

Author: Nikolas Klauser
Date: 2025-01-19T10:28:38+01:00
New Revision: 0cb2fe5183c9b25bb96140c27d12b1ad4a80aa92

URL: https://github.com/llvm/llvm-project/commit/0cb2fe5183c9b25bb96140c27d12b1ad4a80aa92
DIFF: https://github.com/llvm/llvm-project/commit/0cb2fe5183c9b25bb96140c27d12b1ad4a80aa92.diff

LOG: [Clang] Deprecate __is_referenceable (#123185)

`__is_referenceable` is almost unused in the wild, and the few cases I
was able to find had checks around them. Since The places in the
standard library where `__is_referenceable` is used have bespoke
builtins, it doesn't make a ton of sense to keep this builtin around.

See #123078

Added: 
    

Modified: 
    clang/docs/LanguageExtensions.rst
    clang/docs/ReleaseNotes.rst

Removed: 
    


################################################################################
diff  --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst
index 2eb0777dbdc6c8..3aabb4f87fe9b8 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -1697,7 +1697,7 @@ The following type trait primitives are supported by Clang. Those traits marked
 * ``__is_referenceable`` (C++, GNU, Microsoft, Embarcadero):
   Returns true if a type is referenceable, and false otherwise. A referenceable
   type is a type that's either an object type, a reference type, or an unqualified
-  function type.
+  function type. This trait is deprecated and will be removed in Clang 21.
 * ``__is_rvalue_reference`` (C++, Embarcadero)
 * ``__is_same`` (C++, Embarcadero)
 * ``__is_same_as`` (GCC): Synonym for ``__is_same``.

diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 14a3b5db05ff3b..b02ac467cd3a22 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -93,6 +93,11 @@ C++ Specific Potentially Breaking Changes
   few users and can be written as ``__is_same(__remove_cv(T), decltype(nullptr))``,
   which GCC supports as well.
 
+- The type trait builtin ``__is_referenceable`` has been deprecated, since it has
+  very few users and all the type traits that could benefit from it in the
+  standard library already have their own bespoke builtins. It will be removed in
+  Clang 21.
+
 - Clang will now correctly diagnose as ill-formed a constant expression where an
   enum without a fixed underlying type is set to a value outside the range of
   the enumeration's values.
@@ -310,7 +315,7 @@ C++23 Feature Support
 
 - Extend lifetime of temporaries in mem-default-init for P2718R0. Clang now fully
   supports `P2718R0 Lifetime extension in range-based for loops <https://wg21.link/P2718R0>`_.
-  
+
 - ``__cpp_explicit_this_parameter`` is now defined. (#GH82780)
 
 C++20 Feature Support
@@ -717,7 +722,7 @@ Improvements to Clang's diagnostics
 
 - Clang now diagnoses dangling references for C++20's parenthesized aggregate initialization (#101957).
 
-- Fixed a bug where Clang would not emit ``-Wunused-private-field`` warnings when an unrelated class 
+- Fixed a bug where Clang would not emit ``-Wunused-private-field`` warnings when an unrelated class
   defined a defaulted comparison operator (#GH116270).
 
   .. code-block:: c++
@@ -937,7 +942,7 @@ Bug Fixes to C++ Support
 - Fixed an assertion failure caused by invalid default argument substitutions in non-defining
   friend declarations. (#GH113324)
 - Fix a crash caused by incorrect argument position in merging deduced template arguments. (#GH113659)
-- Fixed a parser crash when using pack indexing as a nested name specifier. (#GH119072) 
+- Fixed a parser crash when using pack indexing as a nested name specifier. (#GH119072)
 - Fixed a null pointer dereference issue when heuristically computing ``sizeof...(pack)`` expressions. (#GH81436)
 - Fixed an assertion failure caused by mangled names with invalid identifiers. (#GH112205)
 - Fixed an incorrect lambda scope of generic lambdas that caused Clang to crash when computing potential lambda