[libcxx-commits] [PATCH] D117660: [libc++] Fix a typo in reverse_iterator::operator=

[Casey Carter via Phabricator via libcxx-commits]

CaseyCarter added a comment.

> We should be checking is_assignable<It&, ...>. is_assignable<It, ...> checks for an rvalue left-hand side, which is basically never assignable-to.

On the contrary, `is_assignable<T, U>` is almost always equal to `is_assignable<T&, U>` when `T` is a class type since assignment operators for class types are rarely `&`-qualified. I assume that's how this constraint slipped through testing, which indicates lack of test coverage for e.g. `reverse_iterator<int*>`.

> this is going to be an extra mess as soon as we need to support move-only iterators in reverse_iterator

forward_iterator requires copyable. Move-only iterators are necessarily single-pass, and therefore never valid parameters for `reverse_iterator`.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D117660/new/

https://reviews.llvm.org/D117660