Language

• FnOnce, FnMut, and the Fn traits are now implemented for Box<FnOnce>, Box<FnMut>, and Box<Fn> respectively.
• You can now coerce closures into unsafe function pointers. e.g.

  unsafe fn call_unsafe(func: unsafe fn()) {
      func()
  }
  
  pub fn main() {
      unsafe { call_unsafe(|| {}); }
  }

Compiler

• Added the armv6-unknown-freebsd-gnueabihf and armv7-unknown-freebsd-gnueabihf targets.
• Added the wasm32-unknown-wasi target.

Libraries

• Thread will now show its ID in Debug output.
• StdinLock, StdoutLock, and StderrLock now implement AsRawFd.
• alloc::System now implements Default.
• Expanded Debug output ({:#?}) for structs now has a trailing comma on the last field.
• char::{ToLowercase, ToUppercase} now implement ExactSizeIterator.
• All NonZero numeric types now implement FromStr.
• Removed the Read trait bounds on the BufReader::{get_ref, get_mut, into_inner} methods.
• You can now call the dbg! macro without any parameters to print the file and line where it is called.
• In place ASCII case conversions are now up to 4× faster. e.g. str::make_ascii_lowercase
• hash_map::{OccupiedEntry, VacantEntry} now implement Sync and Send.

Stabilized APIs

• f32::copysign
• f64::copysign
• RefCell::replace_with
• RefCell::map_split
• ptr::hash
• Range::contains
• RangeFrom::contains
• RangeTo::contains
• RangeInclusive::contains
• RangeToInclusive::contains
• Option::copied

Cargo

• You can now set cargo:rustc-cdylib-link-arg at build time to pass custom linker arguments when building a cdylib. Its usage is highly platform specific.

Misc

• The Rust toolchain is now available natively for musl based distros.