---
title: 2024-01-15 Planning meeting
tags: weekly-meeting, T-types
date: 2024-01-15
---

# T-types planning meeting agenda

## Updates

### [Tracking issue for shared type library](https://github.com/rust-lang/types-team/issues/16)

### [Tracking issue for AFIT and RPITIT](https://github.com/rust-lang/types-team/issues/66)

### [Tracking issue for TAITs](https://github.com/rust-lang/types-team/issues/67)

### [Tracking issue for GATs](https://github.com/rust-lang/types-team/issues/68)

### [Tracking issue for a-mir-formality](https://github.com/rust-lang/types-team/issues/69)

### [Tracking issue for subtyping refactor](https://github.com/rust-lang/types-team/issues/70)

### [Tracking issue for implied bounds refactor](https://github.com/rust-lang/types-team/issues/71)

### [Tracking issue for trait object upcasting](https://github.com/rust-lang/types-team/issues/72)

### [Tracking issue for negative impls](https://github.com/rust-lang/types-team/issues/73)

### [Tracking issue for rust trait solver refactor](https://github.com/rust-lang/types-team/issues/76)

### [Model coherence in formality](https://github.com/rust-lang/types-team/issues/103)

### [Normalize in orphan check](https://github.com/rust-lang/types-team/issues/104)

### [New solver in coherence](https://github.com/rust-lang/types-team/issues/105)

### ["Semantic outlives" for opaque aliases](https://github.com/rust-lang/types-team/issues/106)

### [Minimal version of TAITs](https://github.com/rust-lang/types-team/issues/107)

### [Prototype of Polonius](https://github.com/rust-lang/types-team/issues/108)

### [RPIT capture all lifetimes](https://github.com/rust-lang/types-team/issues/110)

### [Enforce where-clauses on type aliases via alias type](https://github.com/rust-lang/types-team/issues/111)

### [Use the new trait solver in all the places](https://github.com/rust-lang/types-team/issues/112)

### [Support negative impls in coherence](https://github.com/rust-lang/types-team/issues/113)

### [Location-sensitive polonius](https://github.com/rust-lang/types-team/issues/114)

### [UnlimiTAIT](https://github.com/rust-lang/types-team/issues/115)

### [Coinduction](https://github.com/rust-lang/types-team/issues/116)

### [Instantiate implied bounds explicitly](https://github.com/rust-lang/types-team/issues/117)

### [Perfect derive](https://github.com/rust-lang/types-team/issues/118)

### [Specialization](https://github.com/rust-lang/types-team/issues/119)

### [Avoid inference guessing in trait solver (e.g., favoring where-clauses over impls)](https://github.com/rust-lang/types-team/issues/120)

### [Avoid bounding impl trait return type by all input type parameters using existential lifetimes](https://github.com/rust-lang/types-team/issues/121)

### [Implied bounds on higher-ranked binders](https://github.com/rust-lang/types-team/issues/122)

### [Full triage of all soundness issues](https://github.com/rust-lang/types-team/issues/123)

## Nominated issues

None.

## Types FCPs

### [Prevent opaque types being instantiated twice with different regions within the same function](https://github.com/rust-lang/rust/pull/116935)

Lang + types. Two open concerns.

### [Allow coercions from never-type when ref binding is involved](https://github.com/rust-lang/rust/pull/118270)

Allows this code to compile:

// check-pass

pub struct Foo {
    bar: u8
}

#[allow(unused_variables)]
fn main() {
    let Foo { ref bar } = loop {};
}

## Major change proposals

None.

## Deep dive planning

### [Variance and Rust](https://github.com/rust-lang/types-team/issues/45)

### [discuss the `trait_alias` feature](https://github.com/rust-lang/types-team/issues/49)

### [Closure return type outlives guarantees](https://github.com/rust-lang/types-team/issues/57)

### [ Account for late-bound lifetimes in generics #103448 ](https://github.com/rust-lang/types-team/issues/62)

### [Negative trait impls check-in](https://github.com/rust-lang/types-team/issues/82)

### [Coinductive trait semantics and normalization](https://github.com/rust-lang/types-team/issues/83)

### [Specialization](https://github.com/rust-lang/types-team/issues/89)

### [Deep dive for leak check/higher ranked fn ptr subtyping](https://github.com/rust-lang/types-team/issues/96)

### [discuss "incorrect implied bounds in wfcheck"](https://github.com/rust-lang/types-team/issues/99)

### [dyn safety and coherence](https://github.com/rust-lang/types-team/issues/100)

### [`'erased` during analysis](https://github.com/rust-lang/types-team/issues/101)

### [unsound issues fun time](https://github.com/rust-lang/types-team/issues/125)