[Issue 24481] retro no longer works with types that support assignment but not moving

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24481

Dlang Bot <dlang-bot at dlang.rocks> changed:

           What    |Removed                     |Added
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--- Comment #1 from Dlang Bot <dlang-bot at dlang.rocks> ---
@jmdavis created dlang/phobos pull request #8969 "Fix bugzilla issue 24481:
retro stopped working" fixing this issue:

- Fix bugzilla issue 24481: retro stopped working

  In an attempt make it so that non-copyable types worked with some of the
  functions in std/range/package.d, they were made to use moves instead of
  assignment, which broke the code for types which work with assignment
  but not moves (which affected the folks at Weka).

  The code checked for assignment but not whether move could be used, and
  that didn't change when the code was changed to use move, meaning that
  the checks didn't match what the code was actually doing.

  So, to support both the non-copyable types and the ones that can be
  assigned to but not moved to, this changes the code so that it uses a
  static if to check whether using move compiles, branching the code based
  on whether move works on not. If move works, it's used. If it doesn't,
  then assignment is used like used to be the case. So, in theory, the
  code that worked previously works again, and the newer functionality of
  being able to use non-copyable types with this code continues to work.

  Discussion here: https://github.com/dlang/phobos/pull/8721

https://github.com/dlang/phobos/pull/8969

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