[PATCH] D33919: [ADT] Make iterable SmallVector template overrides more specific

[Francis Ricci via llvm-commits]

Unfortunately, it appears that InputIterator !=
iterator_traits->input_iterator_tag, as that was one of my original
attempts. However, it looks like std::vector's implementation uses
std::__is_input_iterator, which appears to work so far. I'll finish
testing and update if it works.

On Thu, Jun 8, 2017 at 12:42 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>
> On Wed, Jun 7, 2017 at 2:03 PM Francis Ricci <francisjricci at gmail.com>
> wrote:
>>
>> I tried to stay as close as possible to the check from std::distance,
>> which is the function that will fail to compile if you use the
>> templated override without an iterable type. std::distance doesn't
>> require a forward iterator, it only requires:
>> iterator_traits<_InputIter>::difference_type, which should be defined
>> in the same cases as iterator_traits<_InputIter>::pointer afaik.
>
>
> It still seems best to not diverge from what the standard requires here..
>
> "This overload only participates in overload resolution if InputIt satisfies
> InputIterator." (to quote the more accessible (than the stancdard)
> http://en.cppreference.com/w/cpp/container/vector/assign as an example)
>
> Though maybe it's impractical/not worth the hassle, I'm not sure?
>
> I think it'd be a matter of using enable_if and checking the
> iterator_category from the iterator traits, though.
>
>>
>>
>> On Wed, Jun 7, 2017 at 5:00 PM, David Blaikie <dblaikie at gmail.com> wrote:
>> > Looks a bit different from the is_forward_iterator type check that
>> > libc++
>> > uses. Any idea what the tradeoffs are there? Why this solution is
>> > equivalent/as good/correct?
>> >
>> > (should have test coverage for all 3 variants that are modified)
>> >
>> > On Wed, Jun 7, 2017 at 1:57 PM Francis Ricci via Phabricator
>> > <reviews at reviews.llvm.org> wrote:
>> >>
>> >> fjricci updated this revision to Diff 101813.
>> >> fjricci retitled this revision from "[ADT] Ensure that correct
>> >> overrides
>> >> for SmallVector assign are selected" to "[ADT] Make iterable
>> >> SmallVector
>> >> template overrides more specific".
>> >> fjricci edited the summary of this revision.
>> >> fjricci added a comment.
>> >>
>> >> Add unit test and migrate to iterator SFINAE checks
>> >>
>> >>
>> >> https://reviews.llvm.org/D33919
>> >>
>> >> Files:
>> >>   include/llvm/ADT/SmallVector.h
>> >>   unittests/ADT/SmallVectorTest.cpp
>> >>
>> >>
>> >> Index: unittests/ADT/SmallVectorTest.cpp
>> >> ===================================================================
>> >> --- unittests/ADT/SmallVectorTest.cpp
>> >> +++ unittests/ADT/SmallVectorTest.cpp
>> >> @@ -434,6 +434,15 @@
>> >>    this->assertValuesInOrder(this->theVector, 3u, 1, 2, 3);
>> >>  }
>> >>
>> >> +// Assign test
>> >> +TYPED_TEST(SmallVectorTest, AssignNonIterTest) {
>> >> +  SCOPED_TRACE("AssignTest");
>> >> +
>> >> +  this->theVector.push_back(Constructable(1));
>> >> +  this->theVector.assign(2, 2);
>> >> +  this->assertValuesInOrder(this->theVector, 2u, 2);
>> >> +}
>> >> +
>> >>  // Move-assign test
>> >>  TYPED_TEST(SmallVectorTest, MoveAssignTest) {
>> >>    SCOPED_TRACE("MoveAssignTest");
>> >> Index: include/llvm/ADT/SmallVector.h
>> >> ===================================================================
>> >> --- include/llvm/ADT/SmallVector.h
>> >> +++ include/llvm/ADT/SmallVector.h
>> >> @@ -388,7 +388,8 @@
>> >>    void swap(SmallVectorImpl &RHS);
>> >>
>> >>    /// Add the specified range to the end of the SmallVector.
>> >> -  template<typename in_iter>
>> >> +  template <typename in_iter,
>> >> +            typename = typename
>> >> std::iterator_traits<in_iter>::pointer>
>> >>    void append(in_iter in_start, in_iter in_end) {
>> >>      size_type NumInputs = std::distance(in_start, in_end);
>> >>      // Grow allocated space if needed.
>> >> @@ -426,7 +427,9 @@
>> >>      std::uninitialized_fill(this->begin(), this->end(), Elt);
>> >>    }
>> >>
>> >> -  template <typename in_iter> void assign(in_iter in_start, in_iter
>> >> in_end) {
>> >> +  template <typename in_iter,
>> >> +            typename = typename
>> >> std::iterator_traits<in_iter>::pointer>
>> >> +  void assign(in_iter in_start, in_iter in_end) {
>> >>      clear();
>> >>      append(in_start, in_end);
>> >>    }
>> >> @@ -579,7 +582,8 @@
>> >>      return I;
>> >>    }
>> >>
>> >> -  template<typename ItTy>
>> >> +  template <typename ItTy,
>> >> +            typename = typename std::iterator_traits<ItTy>::pointer>
>> >>    iterator insert(iterator I, ItTy From, ItTy To) {
>> >>      // Convert iterator to elt# to avoid invalidating iterator when we
>> >> reserve()
>> >>      size_t InsertElt = I - this->begin();
>> >> @@ -860,7 +864,8 @@
>> >>      this->assign(Size, Value);
>> >>    }
>> >>
>> >> -  template<typename ItTy>
>> >> +  template <typename ItTy,
>> >> +            typename = typename std::iterator_traits<ItTy>::pointer>
>> >>    SmallVector(ItTy S, ItTy E) : SmallVectorImpl<T>(N) {
>> >>      this->append(S, E);
>> >>    }
>> >>
>> >>
>> >