[PATCH] D79740: Align mapped_iterator::reference type with mapped_iterator::operator*() return value.

[Ivan Kelarev via Phabricator via llvm-commits]

ikelarev added a comment.

@dblaikie
Yes, David, you are right. reverse_iterator should not be used with such implementation. Talking about boost implementation I noticed this thing:

          // By default, dereferencing the iterator yields the same as
          // the function.
          typedef typename ia_dflt_help<
              Reference
  #ifdef BOOST_RESULT_OF_USE_TR1
            , result_of<const UnaryFunc(typename std::iterator_traits<Iterator>::reference)>
  #else
            , result_of<const UnaryFunc&(typename std::iterator_traits<Iterator>::reference)>
  #endif
          >::type reference;

In other words, for the function returning by value boost's transform_iterator::operator* will also return by value without any reference. Like I proposed at the very beginning - explicitly specify "reference" type as the resulting type of the functor. Yes, this solution does not 100% conform to iterator requirements, but it's simple and does not bring any UB into the code. And boost uses this approach.


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  https://reviews.llvm.org/D79740/new/

https://reviews.llvm.org/D79740