[clang] [libcxx] [Clang] Add __builtin_common_reference (PR #121199)

[Erich Keane via cfe-commits]

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@@ -50,3 +50,29 @@ def __builtin_common_type : BuiltinTemplate<
    Template<[Class<"TypeMember">], "HasTypeMember">,
    Class<"HasNoTypeMember">,
    Class<"Ts", /*is_variadic=*/1>]>;
+
+// template <template <class,"
+//                     class,"
+//                     template <class> class,"
+//                     template <class> class> class BasicCommonReferenceT,"
+//           template <class... Args> class CommonTypeT,"
+//           template <class> class HasTypeMember,"
+//           class HasNoTypeMember,"
+//           class... Ts>"
+def __builtin_common_reference : BuiltinTemplate<
+            [Template<[Class<>,
+                       Class<>,
+                       Template<[Class<>]>,
+                       Template<[Class<>]>], "BasicCommonReferenceT">,
+             Template<[Class<"Args", /*is_variadic=*/1>], "CommonTypeT">,
+             Template<[Class<>], "HasTypeMember">,
+             Class<"HasNoTypeMember">,
+             Class<"Ts", /*is_variadic=*/1>]>;
+
+foreach Ref = ["", "lvalue", "rvalue"] in {
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erichkeane wrote:

Sorry if I'm being a little dense here... what is going on for the forloop?

https://github.com/llvm/llvm-project/pull/121199