Skip to content

0.5.0

Choose a tag to compare

View all tags
@vigna vigna released this 10 Feb 13:51
0.5.0
ab5f6a8

[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.

Assets 2
Loading