From a01427612c858c2dc74d8a6b1c34d52da2e9828f Mon Sep 17 00:00:00 2001
From: pierwill <pierwill@users.noreply.github.com>
Date: Mon, 28 Feb 2022 16:11:09 -0600
Subject: [PATCH] Edit `rustc_trait_selection::infer::lattice` docs

Remove mentions of outdated/missing type and filename (`infer.rs` and
`LatticeValue`).
---
 compiler/rustc_infer/src/infer/glb.rs     |  2 ++
 compiler/rustc_infer/src/infer/lattice.rs | 28 +++++++++++++----------
 compiler/rustc_infer/src/infer/lub.rs     |  2 ++
 3 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/compiler/rustc_infer/src/infer/glb.rs b/compiler/rustc_infer/src/infer/glb.rs
index 381097344ec68..e98f33ea86eef 100644
--- a/compiler/rustc_infer/src/infer/glb.rs
+++ b/compiler/rustc_infer/src/infer/glb.rs
@@ -1,3 +1,5 @@
+//! Greatest lower bound. See [`lattice`].
+
 use super::combine::CombineFields;
 use super::lattice::{self, LatticeDir};
 use super::InferCtxt;
diff --git a/compiler/rustc_infer/src/infer/lattice.rs b/compiler/rustc_infer/src/infer/lattice.rs
index c47d476963772..32affd6a14e1c 100644
--- a/compiler/rustc_infer/src/infer/lattice.rs
+++ b/compiler/rustc_infer/src/infer/lattice.rs
@@ -1,23 +1,21 @@
-//! # Lattice Variables
+//! # Lattice variables
 //!
-//! This file contains generic code for operating on inference variables
-//! that are characterized by an upper- and lower-bound. The logic and
-//! reasoning is explained in detail in the large comment in `infer.rs`.
+//! Generic code for operating on [lattices] of inference variables
+//! that are characterized by an upper- and lower-bound.
 //!
-//! The code in here is defined quite generically so that it can be
+//! The code is defined quite generically so that it can be
 //! applied both to type variables, which represent types being inferred,
 //! and fn variables, which represent function types being inferred.
-//! It may eventually be applied to their types as well, who knows.
+//! (It may eventually be applied to their types as well.)
 //! In some cases, the functions are also generic with respect to the
 //! operation on the lattice (GLB vs LUB).
 //!
-//! Although all the functions are generic, we generally write the
-//! comments in a way that is specific to type variables and the LUB
-//! operation. It's just easier that way.
+//! ## Note
 //!
-//! In general all of the functions are defined parametrically
-//! over a `LatticeValue`, which is a value defined with respect to
-//! a lattice.
+//! Although all the functions are generic, for simplicity, comments in the source code
+//! generally refer to type variables and the LUB operation.
+//!
+//! [lattices]: https://en.wikipedia.org/wiki/Lattice_(order)
 
 use super::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use super::InferCtxt;
@@ -27,6 +25,11 @@ use rustc_middle::ty::relate::{RelateResult, TypeRelation};
 use rustc_middle::ty::TyVar;
 use rustc_middle::ty::{self, Ty};
 
+/// Trait for returning data about a lattice, and for abstracting
+/// over the "direction" of the lattice operation (LUB/GLB).
+///
+/// GLB moves "down" the lattice (to smaller values); LUB moves
+/// "up" the lattice (to bigger values).
 pub trait LatticeDir<'f, 'tcx>: TypeRelation<'tcx> {
     fn infcx(&self) -> &'f InferCtxt<'f, 'tcx>;
 
@@ -41,6 +44,7 @@ pub trait LatticeDir<'f, 'tcx>: TypeRelation<'tcx> {
     fn relate_bound(&mut self, v: Ty<'tcx>, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, ()>;
 }
 
+/// Relates two types using a given lattice.
 pub fn super_lattice_tys<'a, 'tcx: 'a, L>(
     this: &mut L,
     a: Ty<'tcx>,
diff --git a/compiler/rustc_infer/src/infer/lub.rs b/compiler/rustc_infer/src/infer/lub.rs
index 57cbe2c54f7ae..bc85a4ac609a7 100644
--- a/compiler/rustc_infer/src/infer/lub.rs
+++ b/compiler/rustc_infer/src/infer/lub.rs
@@ -1,3 +1,5 @@
+//! Least upper bound. See [`lattice`].
+
 use super::combine::CombineFields;
 use super::lattice::{self, LatticeDir};
 use super::InferCtxt;