[libcxx-commits] [PATCH] D116489: [libc++] [API BREAK] Change `fs::path::iterator::iterator_category` to `input_iterator_tag`.

[Arthur O'Dwyer via Phabricator via libcxx-commits]

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Quuxplusone added reviewers: ldionne, EricWF, CaseyCarter, libc++.
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This essentially reverts e02ed1c255d71 and puts in a new fix, which makes `path::iterator` a true C++20 `bidirectional_iterator`, but downgrades it to an `input_iterator` in C++17.

Fixes https://github.com/llvm/llvm-project/issues/37852

However, notice that this makes `*it` do a copy (of a hopefully short string), rather than just returning a reference; that might have perf implications.
And notice that a `for`-loop like `for (auto& elt : path)` will no longer compile (but this is just more evidence that `auto&&` Always Works ;)).
On the plus side, after this patch there is no downside to using `std::reverse_iterator<fs::path::iterator>`... unless I've missed something.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D116489

Files:
  libcxx/include/__filesystem/path_iterator.h
  libcxx/include/__iterator/reverse_iterator.h
  libcxx/test/libcxx/input.output/filesystems/class.path/path.itr/reverse_iterator_produces_diagnostic.verify.cpp
  libcxx/test/std/input.output/filesystems/class.path/path.itr/iterator.pass.cpp
  libcxx/test/std/input.output/filesystems/fs.op.funcs/fs.op.proximate/proximate.pass.cpp

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