[libcxx-commits] [libcxx] [libc++] <algorithm>: __is_callable checks whether the callable can be called with rvalue (PR #73451)

[Louis Dionne via libcxx-commits]

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+//===----------------------------------------------------------------------===//
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ldionne wrote:

This should be a `.verify.cpp` test. Please look at other `.verify.cpp` tests for inspiration, they're really not that hard to write.

To trigger the `static_assert`, you'll have to create a comparator that can't be called as a `F const&` and one that can't be called as a `F&`. You can do

```
struct ConstUncallable {
  void operator()(...) const& = delete;
  void operator()(...) & { implementation }
};

struct NonConstUncallable {
  void operator()(...) const&  { implementation }
  void operator()(...) & = delete;
};
```

With the proper signature as expected by each algorithm, of course.


https://github.com/llvm/llvm-project/pull/73451