[libcxx-commits] [libcxx] [libc++] Avoid constructing additional objects when using map::at (PR #157866)

[Louis Dionne via libcxx-commits]

================
@@ -29,6 +29,15 @@ inline const bool __is_transparent_v<_Tp, _Key, __void_t<typename _Tp::is_transp
 
 #endif
 
+// Two types are considered transparently comparable if `comparator(key, arg)` is equivalent to `comparator(key,
+// <implicit cast to KeyT>(arg))`.
+//
+// This is different from `__is_transparent_v`, which is only a property of the comparator and doesn't provide
+// additional semantic guarantees.
+
----------------
ldionne wrote:

```suggestion
```

https://github.com/llvm/llvm-project/pull/157866