Tracking issue for RFC #2094: non-lexical lifetimes

[aturon]

This is a tracking issue for the RFC "non-lexical lifetimes" (rust-lang/rfcs#2094).

Duplicate of #43234

[aturon]

Work is already underway as part of the impl period; I will let @nikomatsakis adjust the issue description with whatever checklist makes the most sense.

[Manishearth]

Initial infrastructure: #45538

[mark-i-m]

Prototype: #43234

[nikomatsakis]

closing in favor of #43234