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https://issues.apache.org/jira/browse/MESOS-7142?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andrew Schwartzmeyer reassigned MESOS-7142:
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Assignee: Michael Park (was: Andrew Schwartzmeyer)
> Revisit MSVC decltype bug
> -------------------------
>
> Key: MESOS-7142
> URL: https://issues.apache.org/jira/browse/MESOS-7142
> Project: Mesos
> Issue Type: Improvement
> Environment: Windows with Visual Studio 2017 RC
> Reporter: Andrew Schwartzmeyer
> Assignee: Michael Park
> Priority: Minor
> Labels: libprocess, windows
> Original Estimate: 2h
> Remaining Estimate: 2h
>
> Review https://reviews.apache.org/r/56781/ works around an existent and
> acknowledged bug in MSVC. From MSVC team:
> {quote}
> I have preprocessed file from Andy yesterday, thank you. I can verify that
> this is a bug in the latest compiler where it’s failing to get the right
> context for the decltype expression for the return type of function. However,
> MSVC does deduce the right type from the return expression in the body. We
> have a bug in the compiler logged now and will be tracked for next release.
> We’ll be adding Mesos project to our daily RealWorld Testing set from now on
> as continuous validation for MSVC compiler. Thank you for bringing this up to
> our attention.
> template <typename F>
> auto then(F&& f) const-> decltype(this->then(std::forward<F>(f), Prefer()))
> Should really expand to this expression, but it’s failing.
> template <typename F>
> auto then(F&& f) const -> decltype(static_cast<const
> Future<T>*>(this)->then(std::forward<F>(f), Prefer()))
> The workaround from Michael to skip explicit return type for auto function
> should be actually better source change for MSVC compiler. For completeness
> sake, you can also just remove ‘this->’ from the decltype expression to make
> it work for MSVC compiler
> -> decltype(then(std::forward<F>(f), Prefer()))
> Another thing worth pointing out is, adding ‘this->’ in the body of the
> function shows that MSVC does correctly deduce the return type.
> template <typename F>
> auto then(F&& f) const
> // -> decltype(then(std::forward<F>(f), Prefer()))
> // -> decltype(static_cast<const
> Future<T>*>(this)->then(std::forward<F>(f), Prefer()))
> {
> return this->then(std::forward<F>(f), Prefer());
> }
> {quote}
> This issue tracks revisiting the work-around when the first patch to VS2017
> is released, as the compiler bug itself should be fixed then.
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