microsoft / microsoft/STL

Many view iterators do not contain an `_Unwrapped()` member function

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Description

While implementing tests for #2991, I noticed that view iterators are always _Is_nothrow_unwrappable_v; this is because _Get_unwrap() does no work on them, as they don't have _Unwrapped() member functions.

It would be good to add _Unwrapped() member functions which return the same iterator, but use the unwrapped base -- for example, filter_view<_It, _Pr>::_Unwrapped() would return filter_view<_Unwrapped_t<_It>, _Pr>. You can see existing uses of this in reverse_iterator and move_iterator.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
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Research direction

Start by reading the existing _Unwrapped() implementations in reverse_iterator and move_iterator, then locate the view iterator classes affected by this issue. Add matching members that return the iterator with its unwrapped base, and use the tests being implemented for #2991 to verify the nothrow-unwrappable behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
compilers
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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