[clang-tools-extra] [libc] [libcxx] [compiler-rt] [flang] [clang] [llvm] [libcxx] Unifying __is_trivial_equality_predicate and __is_trivial_plus_operation into __desugars_to (PR #68642)

[Anton Rydahl via cfe-commits]

================
@@ -18,8 +18,11 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Pred, class _Lhs, class _Rhs>
-struct __is_trivial_plus_operation : false_type {};
+template <class _Operation, class _Canonical>
----------------
AntonRydahl wrote:

Hi @ldionne!

I am unsure about what I am supposed to do with the following:
```C++
template <class _Tp, class _Up> struct __desugars_to<__equal_tag, __equal, _Tp, _Up> : true_type {};
```
Do we want to match the function from `include/__algorithm/equal.h`?

https://github.com/llvm/llvm-project/pull/68642