This is a tracking issue for the RFC "Finalize syntax and parameter scoping for impl Trait, while expanding it to arguments" (rust-lang/rfcs#1951).

Steps:

• Implement the RFC (cc @rust-lang/lang, @rust-lang/compiler -- can anyone write up mentoring instructions?)
• Adjust documentation (see instructions on forge)
• Stabilization PR (see instructions on forge)

Unresolved questions:

• The precedence rules around impl Trait + 'a need to be nailed down.

Known bugs:

(this list is not necessarily exhaustive)

• rustc stack overflow