MVP Stabilization

We are currently focused on stabilizing a Minimum Viable Product form of GATs in rust-lang/rust#96709. That's a long github thread, so this page summarizes the key points to understand.

• Understanding GATs in general:
  • The explainer covers the design that is being stabilized in tutorial form.
  • The design patterns section covers ways that GATs used in the wild.
  • The rough edges section explains some of the ways GATs are currently difficult to use; the shiny future section contains speculation on how to address those.
• Highlights from the thread:
  • The stabilization report lays the groundwork.
  • This summary comment identified the core concerns. We have detailed them here in more depth, and provided some counterpoints:
    • GATs permit complex patterns that will, on net, make Rust harder to use
    • Stabilizing GATs with lifetimes only would help prevent this
    • GATs are useful but the current state is too rough and should not be stabilized
    • Given the number of papercuts, how do we know that the current MVP is forwards compatible with the fixes?
  • One detailed question was raised, about the specifics of our rules for required bounds:
    • Do we have the right rules for required bounds?
• Current status:
  • We are currently awaiting checkboxes to move to final comment period. The fcp merge comment includes a detailed write-up of the questions being considered by the lang and types teams.

Places where conversation has been happening?

Want to read the firehose? Check out these places where conversation has been happening:

• rust-lang/rust#96709 issue thread
• Zulip thread on GATs and complexity
• Zulip thread on "type-GATs vs lifetime-GATs"
• Zulip thread on renaming for -- side topic that spun out