rustversion

• Set RUSTVERSION=1 during rustc --version command (#68)

• Turn off clippy incompatible_msrv in rustversion-conditional code (#63)

• Support -Zfmt-debug=none (#61)

• Documentation improvements

• Documentation improvements

• Support MIRAI (https://github.com/endorlabs/MIRAI)

• Support Windows builds that have OUT_DIR prefixed with \\?\ (#51)

• Resolve unexpected_cfgs warning (#48)

• Recognize $RUSTC_WRAPPER environment variable (#47)

• Documentation improvements

• ~1500 changes, numerous bugfixes

Highlights

• The vast majority of the standard library is now #[stable]. It is no longer possible to use unstable features with a stable build of the compiler.
• Many popular crates on crates.io now work on the stable release channel.
• Arithmetic on basic integer types now checks for overflow in debug builds.

Language

• Several restrictions have been added to trait coherence in order to make it easier for upstream authors to change traits without breaking downstream code.
• Digits of binary and octal literals are lexed more eagerly to improve error messages and macro behavior. For example, 0b1234 is now lexed as 0b1234 instead of two tokens, 0b1 and 234.
• Trait bounds are always invariant, eliminating the need for the PhantomFn and MarkerTrait lang items, which have been removed.
• "-" is no longer a valid character in crate names, the extern crate "foo" as bar syntax has been replaced with extern crate foo as bar, and Cargo now automatically translates "-" in package names to underscore for the crate name.
• Lifetime shadowing is an error.
• Send no longer implies 'static.
• UFCS now supports trait-less associated paths like MyType::default().
• Primitive types now have inherent methods, obviating the need for extension traits like SliceExt.
• Methods with Self: Sized in their where clause are considered object-safe, allowing many extension traits like IteratorExt to be merged into the traits they extended.
• You can now refer to associated types whose corresponding trait bounds appear only in a where clause.
• The final bits of OIBIT landed, meaning that traits like Send and Sync are now library-defined.
• A Reflect trait was introduced, which means that downcasting via the Any trait is effectively limited to concrete types. This helps retain the potentially-important "parametricity" property: generic code cannot behave differently for different type arguments except in minor ways.
• The unsafe_destructor feature is now deprecated in favor of the new dropck. This change is a major reduction in unsafe code.

Libraries

• The thread_local module has been renamed to std::thread.
• The methods of IteratorExt have been moved to the Iterator trait itself.
• Several traits that implement Rust's conventions for type conversions, AsMut, AsRef, From, and Into have been centralized in the std::convert module.
• The FromError trait was removed in favor of From.
• The basic sleep function has moved to std::thread::sleep_ms.
• The splitn function now takes an n parameter that represents the number of items yielded by the returned iterator instead of the number of 'splits'.
• On Unix, all file descriptors are CLOEXEC by default.
• Derived implementations of PartialOrd now order enums according to their explicitly-assigned discriminants.
• Methods for searching strings are generic over Patterns, implemented presently by &char, &str, FnMut(char) -> bool and some others.
• In method resolution, object methods are resolved before inherent methods.
• String::from_str has been deprecated in favor of the From impl, String::from.
• io::Error implements Sync.
• The words method on &str has been replaced with split_whitespace, to avoid answering the tricky question, 'what is a word?'
• The new path and IO modules are complete and #[stable]. This was the major library focus for this cycle.
• The path API was revised to normalize ., adjusting the tradeoffs in favor of the most common usage.
• A large number of remaining APIs in std were also stabilized during this cycle; about 75% of the non-deprecated API surface is now stable.
• The new string pattern API landed, which makes the string slice API much more internally consistent and flexible.
• A new set of generic conversion traits replaced many existing ad hoc traits.
• Generic numeric traits were completely removed. This was made possible thanks to inherent methods for primitive types, and the removal gives maximal flexibility for designing a numeric hierarchy in the future.
• The Fn traits are now related via inheritance and provide ergonomic blanket implementations.
• The Index and IndexMut traits were changed to take the index by value, enabling code like hash_map["string"] to work.
• Copy now inherits from Clone, meaning that all Copy data is known to be Clone as well.

Misc

• Many errors now have extended explanations that can be accessed with the --explain flag to rustc.
• Many new examples have been added to the standard library documentation.
• rustdoc has received a number of improvements focused on completion and polish.
• Metadata was tuned, shrinking binaries by 27%.
• Much headway was made on ecosystem-wide CI, making it possible to compare builds for breakage.