edition-changes.md

2018-Specific Changes

The following is a summary of changes that only apply to code compiled with the 2018 edition compared to the 2015 edition.

Rust

• Non-lexical lifetimes (future inclusion planned for 2015 edition)
• At most once ? macro repetition operator.
• Path changes:
  • use declarations must begin with:
    • crate – refers to the current crate.
    • self – refers to the current module.
    • super – refers to the parent module.
    • An external crate name.
    • :: – must be followed by an external crate name. This is required if an external crate has the same name as an in-scope item, to catch possible ambiguities with uniform paths (which is planned for inclusion soon #55618).
  • Paths in pub(in path) visibility modifiers must start with crate, self, or super.
• Anonymous trait function parameters are not allowed.
  • Trait function parameters may use any irrefutable pattern when the function has a body.
• dyn is a strict keyword, in 2015 it is a weak keyword.
• async, await, and try are reserved keywords.
• The following lints are now deny by default:
  • overflowing_literals
  • tyvar_behind_raw_pointer

Cargo

• If there is a target definition in a Cargo.toml manifest, it no longer automatically disables automatic discovery of other targets.
• Target paths of the form src/{target_name}.rs are no longer inferred for targets where the path field is not set.
• cargo install for the current directory is no longer allowed, you must specify cargo install --path . to install the current package.