Implement associated items

[alexcrichton]

Tracking issue for rust-lang/rfcs#195

This meta-bug contains links to the most significant tasks remaining for associated items. For a comprehensive listing of bugs, please search using the A-associated-items label.

Post 1.0 Tasks

• Normalize associated types used in where clauses (Normalization of projections in where clauses #20765) and associated type bounds (Normalization of projections in trait bounds on associated types #20775)
• Implement associated lifetimes (see Issue subtask of RFC 195: implement associated lifetimes #17842),
• Update library code for associated constants (see Issue identify traits in libstd that should use associated constants #17825).

Completed Tasks

• Implement associated output types (see PR librustc: Implement associated types behind a feature gate. #16377),
• Update library code for associated output types (see Issue identify traits in libstd that should use associated types (as output parameters) #17826),
• Implement multi-dispatch (see PR Implement multidispatch and conditional dispatch. #17669),
• Update library code for multi-dispatch (see Issue identify traits in libstd that should use multidispatch  #17827),
• ICE: Unbound path ICE with associated types: unbound path #17388
• Clarify outlives requirements on projected types (Clarify outlives requirements on associated types #20303)
• Integrate projection types into method dispatch Integrate projection types into method dispatch #20469
• Some types not normalized? Associated types may not all be normalized #20604
• ICE with missing impl items ICE due to missing associated type in trait implementation #20347
• Associated types should permit builtin bounds (Support builtin bounds on associated types and make them Sized by default #17921)
• Implement Trait<Out=Type> syntax (Support the Trait<Output=Type> syntax #18432)
• Support T::Type syntax (Support T::Type shorthand for referencing associated types #18433)
• Associated types are used as inputs for multidispatch (Associated types are used as inputs for multidispatch #18437)
• Traits with associated types appearing on structs, enums, or other traits (Traits with associated types appearing on structs, enums or other traits #18768)
• Qualified paths don't check type arguments in the trait reference (Qualified paths don't consider the type arguments supplied to the trait #18865)
• rustdoc panics when dealing with associated types (rustdoc panics when dealing with associated types #18594)
• Associated types should permit arbitrary bounds (Associated types should permit arbitrary bounds #18178)
• Associated types need to do transitive bound expansion (Associated types need to do transitive bound expansion #18434)
• Traits with where clauses that themselves reference traits with assoc types (Traits with where clauses that themselves reference associated types #18436)
• Integrate object projection predicates into rustdoc (Integrate object projection predicates into rustdoc #20299)
• Convert T::Foo resolution to use where clauses, not bounds (Convert T::Foo resolution to use where clauses, not bounds #20300)
• Implement associated constants (see Issue subtask of RFC 195: Implement associated constants #17841),
• Implement defaults for associated types (see issue Implement defaults for associated types #19476),

Declined tasks

• Permit unqualified references to associated types of the trait within the trait definition (Permit unqualified references to associated types of the trait within the trait definition #18764)
• Update library code for associated lifetimes (see Issue identify traits in libstd that should use associated lifetimes #17828),

[pnkfelix]

there is debate about whether this contains P-backcompat-lang issues for 1.0, or if the 1.0 issues are solely P-backcompat-libs.

Leaving as I-nominated so that people can take a week teasing apart the sub-issues that stem from the RFC.

[pnkfelix]

leaving I-nominated for anohter week again! assigning to myself to spawn off subissues.

[pnkfelix]

punting for another week...

[aturon]

@pnkfelix Want to coordinate this work this week? I want to do an evaluation of how much of associated items has landed in terms of what we need for the libraries, and that could help inform the division into subissues/nominations. Let me know.

[pnkfelix]

@aturon sure, happy to coordinate. I'm going to actually look at it now; I will either open subissues directly, or, if I do not feel comfortable doing so, then I'll email you with my findings.

[pnkfelix]

Okay I think I've opened all the subbugs I can think of, and my spreadsheet (google doc) at least represents a hackish sketch of what might need to do be done (though I did not look at libserialize, std::ascii, nor std::io yet.

Anyway, if this sits idle until the next triage meeting, my official recommendation is that we nominate one or more of the tickets that I opened that point to this ticket, and then we remove the nomination from this ticket (since it is a metabug, quite literally now).