Improve compile error from using Gen constructor incorrectly #170
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The test failure log says that apt-get failed to retrieve some packages due to a network timeout. I guess the test needs to be retried later? |
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@cirodrig you can force travis to redo the job if you somehow alter the PR. One simple way is simply rebasing + force push. Project owner can manually re-trigger specific jobs and builds. |
emil-e
requested changes
Sep 17, 2017
include/rapidcheck/Gen.hpp
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| : m_impl(new GenImpl<Decay<Impl>>(std::forward<Impl>(impl))) { | ||
| static_assert(MakesShrinkable<T, Decay<Impl>>::value, | ||
| "Generator implementation must have a method Shrinkable<T> operator()(const Random &, int) const"); | ||
| static_assert(std::is_copy_constructible<Decay<Impl>>::value, |
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It shouldn't actually need to be copyable, have you tried not having a copy constructor? I know the doc comment says it does but I think that's incorrect.
include/rapidcheck/Gen.hpp
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| // Concept check for types that have method | ||
| // `Shrinkable<T> G::operator()(const Random &, int) const` | ||
| template<typename T, typename G, typename = void> | ||
| struct MakesShrinkable : std::false_type {}; |
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Wouldn't it be simpler to do:
using MakesShrinkable = std::is_convertible<decltype(std::declval<const G>()(std::declval<Random>(), 0)), Shrinkable<T>>;
(Save for possible typos on my part)
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Didn't realize I could do that. Made both changes.
…atible type This produces a compile error in Gen's constructor. Before this change, errors would be attributed to GenImpl.
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This change improves compile-time error reporting for a kind of error that I faced when I was learning to use rapidcheck. If
Gen<T>is constructed from a lambda that returns the wrong type, the compiler would report errors inGenImpl. This change reports an error inGen's constructor, which otherwise would not have an error.An example where error reporting is useful: