Language

• Non-Lexical Lifetimes are now enabled on the 2015 edition.
• The order of traits in trait objects no longer affects the semantics of that object. e.g. dyn Send + fmt::Debug is now equivalent to dyn fmt::Debug + Send, where this was previously not the case.

Libraries

• HashMap's implementation has been replaced with hashbrown::HashMap implementation.
• TryFromSliceError now implements From<Infallible>.
• mem::needs_drop is now available as a const fn.
• alloc::Layout::from_size_align_unchecked is now available as a const fn.
• String now implements BorrowMut<str>.
• io::Cursor now implements Default.
• Both NonNull::{dangling, cast} are now const fns.
• The alloc crate is now stable. alloc allows you to use a subset of std (e.g. Vec, Box, Arc) in #![no_std] environments if the environment has access to heap memory allocation.
• String now implements From<&String>.
• You can now pass multiple arguments to the dbg! macro. dbg! will return a tuple of each argument when there is multiple arguments.
• Result::{is_err, is_ok} are now #[must_use] and will produce a warning if not used.

Stabilized APIs

• VecDeque::rotate_left
• VecDeque::rotate_right
• Iterator::copied
• io::IoSlice
• io::IoSliceMut
• Read::read_vectored
• Write::write_vectored
• str::as_mut_ptr
• mem::MaybeUninit
• pointer::align_offset
• future::Future
• task::Context
• task::RawWaker
• task::RawWakerVTable
• task::Waker
• task::Poll

Cargo

• Cargo will now produce an error if you attempt to use the name of a required dependency as a feature.
• You can now pass the --offline flag to run cargo without accessing the network.

You can find further change's in Cargo's 1.36.0 release notes.

Clippy

There have been numerous additions and fixes to clippy, see Clippy's 1.36.0 release notes for more details.

Misc

Compatibility Notes

• With the stabilisation of mem::MaybeUninit, mem::uninitialized use is no longer recommended, and will be deprecated in 1.39.0.