0.8.0

[0.8.0] - 2026-07-10

Changed

• MaybeDangling does not need anymore to implement Debug.

• peek_mut is now unsafe, as it could lead to UB.

Fixed

• Peekable/Flatten drop order and leaks have been fixed.

• StepBy was misstepping by one on a fresh iterator.

• FusedLender/FallibleFusedLender were not implementing correctly last.

• TakeWhile was no honoring the fused contract.

• Take backward advancing methods were not behaving correctly when
  taking zero elements or advancing by zero elements.

• Chunky does not panic anymore on an advancing operation that
  exhaust the underlying lender.

• from_iter_ref now drops the held element before getting the next one.

0.7.0

[0.7.0] - 2026-05-31

New

• Functions __check_lender_covariance, __check_fallible_lender_covariance,
  __check_lending_covariance and __check_fallible_lending_covariance to
  check covariance of lenders and lends in custom implementations.

• Many sources and accessors are now const fn, so they can be used in
  const contexts (e.g., from_iter, from_into_iter, from_iter_ref,
  from_fn, once_with, windows_mut, and array_windows_mut).

Fixed

• find_map implementations were missing covariance checks.

• Removed spurious &'short reference from fallible covariance checks.

Changed

• Following std's policy, we have #[inline] on all public methods.

• We have now resolver = 3, which should solve some update issues
  with the maybe-dangling crate.

0.6.2

[0.6.2] - 2026-02-18

Fixed

• Missing lifetimes in PhantomData was causing compiler
  errors when using #![with] with covariance-check macros.

0.6.1

[0.6.1] - 2026-02-18

Fixed

• Closed loophole in covariance-checking macro that was
  skipping covariance checks when using elided lifetimes.

• Now macros use $crate:: to refer to internal items.

• Ported documentation about #![with].

0.6.0

Change Log

[0.6.0] - 2026-02-17

New

• Major improvement to the covariance check: it is no longer possible to
  circumvent it using core::ptr::null(), todo!(), unimplemented!(),
  panic!(), loop {}, etc.

• Convenience Lender::lender_by_ref method that is equivalent to
  iter followed by into_ref_lender.

Fixed

• FilterMap, Scan, and MapWhile (both standard and fallible) had an
  additional parameter that was forcing a 'static bound when extending the
  trait. Now they are structured like Map.

0.5.2

[0.5.2] - 2026-02-15

New

• Convenience Lender::lender_by_ref method that is equivalent to
  iter followed by into_ref_lender.

Fixed

• FilterMap, Scan, and MapWhile (both standard and fallible) had an
  additional parameter that was forcing a 'static bound when extending the
  trait. Now they are structured like Map.

0.5.1

[0.5.1] - 2026-02-14

New

• New FromIterRef (fallible) source to create lenders from references to
  elements returned by iterators. Accessible through the
  into_ref_lender/into_fallible_ref_lender extension methods.

0.5.0

[0.5.0] - 2026-02-10

New

• New infrastructure to check covariance of lends. Every implementation must
  use either the (safe) check_covariance!/check_covariance_fallible! macros
  (for sources) to check covariance of the lend lifetime, or the (unsafe)
  unsafe_assume_covariance!/unsafe_assume_covariance_fallible! macros when
  assuming covariance of underlying lends (without any check). Methods that used
  to take for<'all> Lending<'all> now take CovariantLending, which depends
  on for<'all> Lending<'all, L> but forces a covariance check.

• Covariance checks have also been embedded in the covar!, covar_mut! and
  covar_once macros (formerly hrc...), which are now required to pass a
  closure, as closures are passed through the Covar wrapper, which forces
  a covariance check. This unfortunately includes closures without lifetimes.

• Added missing FromFallibleLender/ExtendFallibleLender traits.

• The Convert adapter is now accessible through the Lender::convert method.

Improved

• windows_mut is now double-ended.

• Fallible lenders have now feature parity with normal lenders. In particular,
  FallibleLender has now chunk and rposition methods.

• Thanks to AliasableBox and MaybeDangling we now pass miri.

• FallibleLender::advance_by/FallibleLender::advance_back_by have now a
  signature aligned with Lender::advance_by/Lender::advance_back_by.

• Completed implementation of standard traits (Debug, Clone, Default, etc.)
  where possible.

Changed

• Macros hrc, hrc_mut and hrc_once have been renamed to covar, covar_mut
  and covar_once, respectively.

• Windows and array windows must have a non-zero length, as in Iterator,
  and they implement FusedLender and ExactSizeLender.

• The return type of Peekable::peek is now Option<&'_ Lend<'_, L>>, which
  fixes a problem of data escape. Analogously for FalliblePeekable::peek.

• The lend! macro now covers just a set of fixed covariant types. If you need
  to use more complex types, you can use the covariant_lend! macro, which
  however requires that you define a type name (with an optional
  visibility specifier), as it cannot be inlined. The same applies to
  fallible_lend! and covariant_fallible_lend!.

• Coherent use of must_use attribute.

• Fallible sources and adapters are now uniformly in separate modules with the
  same name of the standard ones and are renamed in mod.rs.

• Fallible once, repeat, etc. now follow the fallible_iterator design,
  with specific methods like once_err, repeat_err, etc. to generate
  errors.

• FallibleFusedLender guarantees Ok(None) to repeat, but does not
  have anymore a guarantee of behavior after an error (like it
  happens with fallible_iterator).

• min/max now require Ord, like the standard Iterator methods.

• IntoFallible now uses Infallible as fixed error type, like
  fallible_iterator.

Fixed

• Several possible UBs are no longer possible thanks to the new covariance
  checking infrastructure.

• Peekable and FalliblePeekable are now deallocating their fields
  in the correct order.

• All implementations propagate correctly fused, double-ended and exact-size
  traits.

• max/max_by return the last instance in case of ties, as in Iterator
  (previously they returned the first instance).

• All repeat method return (usize::MAX, None) on size_hint, as in Iterator,
  if they return a value, or (0, Some(0)) if they return an error.

• The order of parameters (lend/error) in a few methods was inconsistent.

• Removed Clone implementation that could lead to UB from Peekable and
  FlattenCompat.

0.4.2

[0.4.2] - 2025-11-18

Fixed

• Fixed flatten when one of the lenders is empty.

0.4.1

[0.4.1] - 2025-11-15

• Significant API expansion with the addition of fallible lenders,
  which return a result containing an option.