tmp/tmpkbyae3dz/{from.md → to.md}
RENAMED
|
@@ -0,0 +1,24 @@
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 1 |
+
### [[concepts]]: concepts library <a id="diff.cpp20.concepts">[[diff.cpp20.concepts]]</a>
|
| 2 |
+
|
| 3 |
+
**Change:** Replace `common_reference_with` in
|
| 4 |
+
`three_way_comparable_with`, `equality_comparable_with`, and
|
| 5 |
+
`totally_ordered_with` with an exposition-only concept. **Rationale:**
|
| 6 |
+
Allow uncopyable, but movable, types to model these concepts. **Effect
|
| 7 |
+
on original feature:** Valid C++20 code relying on subsumption with
|
| 8 |
+
`common_reference_with` may fail to compile in this revision of C++. For
|
| 9 |
+
example:
|
| 10 |
+
|
| 11 |
+
``` cpp
|
| 12 |
+
template<class T, class U>
|
| 13 |
+
requires equality_comparable_with<T, U>
|
| 14 |
+
bool attempted_equals(const T&, const U& u); // previously selected overload
|
| 15 |
+
|
| 16 |
+
template<class T, class U>
|
| 17 |
+
requires common_reference_with<const remove_reference_t<T>&, const remove_reference_t<U>&>
|
| 18 |
+
bool attempted_equals(const T& t, const U& u); // ambiguous overload; previously
|
| 19 |
+
// rejected by partial ordering
|
| 20 |
+
bool test(shared_ptr<int> p) {
|
| 21 |
+
return attempted_equals(p, nullptr); // ill-formed; previously well-formed
|
| 22 |
+
}
|
| 23 |
+
```
|
| 24 |
+
|