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| author | Casey Carter <cacarter@microsoft.com> | 2021-12-23 14:56:59 -0800 |
|---|---|---|
| committer | Evergreen Agent <no-reply@evergreen.mongodb.com> | 2022-04-04 21:09:18 +0000 |
| commit | 6fe4ec2625b638abb709a002c765d23cfe9e4fd6 (patch) | |
| tree | 989cd657d9f063be911998230777cb19286a76d9 | |
| parent | c911a489290153d7154dfc9fbe85c1739e7d4e19 (diff) | |
| download | mongo-6fe4ec2625b638abb709a002c765d23cfe9e4fd6.tar.gz | |
SERVER-62498 Non-`const` `unique_function` should not convert to `std::function` even after LWG-2774
[LWG-2774](https://wg21.link/lwg2774) changes `std::function`'s converting constructor to accept its argument by forwarding reference. With that change implemented, that constructor becomes a better match for non-`const` `unique_function` arguments than `unique_function`'s `const`-qualified deleted conversion operator template to `std::function`. As a result, `std::is_convertible_v<unique_function<T>, std::function<T>>` changes from `false` to `true` when Standard Libraries implement LWG-2774. (MSVC recently implemented this LWG issue in https://github.com/microsoft/STL/pull/2098 and noticed the `unique_function` test failing as a result.)
I believe the fix is to add another deleted conversion operator template that is not `const`-qualified to `unique_function`. This makes the test pass locally, as well as correcting a simplified test case with GCC trunk (https://github.com/microsoft/STL/pull/2098) which I believe also implements LWG-2774.
Closes https://github.com/mongodb/mongo/pull/1437
Signed-off-by: Blake Oler <blake.oler@mongodb.com> and Billy Donahue <billy.donahue@mongodb.com>
| -rw-r--r-- | src/mongo/util/functional.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/src/mongo/util/functional.h b/src/mongo/util/functional.h index 9f353343b69..a680e54a266 100644 --- a/src/mongo/util/functional.h +++ b/src/mongo/util/functional.h @@ -231,6 +231,8 @@ public: // NOTE: This is not quite able to disable all `std::function` conversions on MSVC, at this // time. template <typename Signature> + operator std::function<Signature>() = delete; + template <typename Signature> operator std::function<Signature>() const = delete; private: |