Rust 1.26.0

Language

• Closures now implement Copy and/or Clone if all captured variables implement either or both traits.
• The inclusive range syntax e.g. for x in 0..=10 is now stable.
• The '_ lifetime is now stable. The underscore lifetime can be used anywhere a lifetime can be elided.
• impl Trait is now stable allowing you to have abstract types in returns or in function parameters. E.g. fn foo() -> impl Iterator<Item=u8> or fn open(path: impl AsRef<Path>).
• Pattern matching will now automatically apply dereferences.
• 128-bit integers in the form of u128 and i128 are now stable.
• main can now return Result<(), E: Debug> in addition to ().
• A lot of operations are now available in a const context. E.g. You can now index into constant arrays, reference and dereference into constants, and use tuple struct constructors.
• Fixed entry slice patterns are now stable. E.g.

  let points = [1, 2, 3, 4];
  match points {
      [1, 2, 3, 4] => println!("All points were sequential."),
      _ => println!("Not all points were sequential."),
  }

Compiler

• LLD is now used as the default linker for wasm32-unknown-unknown.
• Fixed exponential projection complexity on nested types. This can provide up to a ~12% reduction in compile times for certain crates.
• Added the --remap-path-prefix option to rustc. Allowing you to remap path prefixes outputted by the compiler.
• Added powerpc-unknown-netbsd target.

Libraries

• Implemented From<u16> for usize & From<{u8, i16}> for isize.
• Added hexadecimal formatting for integers with fmt::Debug e.g. assert!(format!("{:02x?}", b"Foo\0") == "[46, 6f, 6f, 00]")
• Implemented Default, Hash for cmp::Reverse.
• Optimized str::repeat being 8x faster in large cases.
• ascii::escape_default is now available in libcore.
• Trailing commas are now supported in std and core macros.
• Implemented Copy, Clone for cmp::Reverse
• Implemented Clone for char::{ToLowercase, ToUppercase}.

Stabilized APIs

• *const T::add
• *const T::copy_to_nonoverlapping
• *const T::copy_to
• *const T::read_unaligned
• *const T::read_volatile
• *const T::read
• *const T::sub
• *const T::wrapping_add
• *const T::wrapping_sub
• *mut T::add
• *mut T::copy_to_nonoverlapping
• *mut T::copy_to
• *mut T::read_unaligned
• *mut T::read_volatile
• *mut T::read
• *mut T::replace
• *mut T::sub
• *mut T::swap
• *mut T::wrapping_add
• *mut T::wrapping_sub
• *mut T::write_bytes
• *mut T::write_unaligned
• *mut T::write_volatile
• *mut T::write
• Box::leak
• FromUtf8Error::as_bytes
• LocalKey::try_with
• Option::cloned
• btree_map::Entry::and_modify
• fs::read_to_string
• fs::read
• fs::write
• hash_map::Entry::and_modify
• iter::FusedIterator
• ops::RangeInclusive
• ops::RangeToInclusive
• process::id
• slice::rotate_left
• slice::rotate_right
• String::retain

Cargo

• Cargo will now output path to custom commands when -v is passed with --list
• The Cargo binary version is now the same as the Rust version

Misc

• The second edition of "The Rust Programming Language" book is now recommended over the first.

Compatibility Notes

• aliasing a Fn trait as dyn no longer works. E.g. the following syntax is now invalid.
  use std::ops::Fn as dyn;
  fn g(_: Box<dyn(std::fmt::Debug)>) {}
• The result of dereferences are no longer promoted to 'static. e.g.

  fn main() {
      const PAIR: &(i32, i32) = &(0, 1);
      let _reversed_pair: &'static _ = &(PAIR.1, PAIR.0); // Doesn't work
  }

• Deprecate AsciiExt trait in favor of inherent methods.
• ".e0" will now no longer parse as 0.0 and will instead cause an error.
• Removed hoedown from rustdoc.
• Bounds on higher-kinded lifetimes a hard error.