[libcxx-commits] [PATCH] D106827: [libc++] Implement the resolution for LWG3522 in all language modes.

[Arthur O'Dwyer via Phabricator via libcxx-commits]

Quuxplusone added inline comments.


================
Comment at: libcxx/test/std/containers/container.adaptors/priority.queue/priqueue.cons/ctor_iter_constraint.compile.pass.cpp:21
+static_assert( std::is_constructible<std::vector<int>, int, int>::value, "");
+static_assert(!std::is_constructible<std::priority_queue<int>, int, int>::value, "");
----------------
I had initially written this test as follows, to test SFINAE-friendliness; but during the rebase I temporarily forgot why I'd done that, and changed it to the much simpler (but not-testing-SFINAE) version you see above. If you want me to change back to the SFINAE version, I can.
```
template<class Seq>
std::true_type test(int, decltype(Seq(1,2))) { return {}; }

template<class Seq>
std::false_type test(long, Seq) { return {}; }

int main(int, char**)
{
    // Sanity-check that std::vector<int>(1,2) is well-formed.
    auto vector_is_constructible = test< std::vector<int> >(1, {});
    static_assert(decltype(vector_is_constructible)::value, "");

    // LWG3522: std::priority_queue<int>(1,2) is NOT well-formed.
    auto pq_is_constructible = test< std::priority_queue<int> >(1, {});
    static_assert(!decltype(pq_is_constructible)::value, "");

    return 0;
}
```


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D106827/new/

https://reviews.llvm.org/D106827