Move unify_key module.

From `rustc_middle::infer` to `rustc_infer::infer`. Because everything
in it is only used within `rustc_infer`, and no longer needs to be
`pub`. Plus it's always good to make the huge `rustc_middle` crate
smaller.

compiler/rustc_infer/src/infer/mod.rs

@@ -26,7 +26,6 @@ use rustc_macros::extension;
 pub use rustc_macros::{TypeFoldable, TypeVisitable};
 use rustc_middle::bug;
 use rustc_middle::infer::canonical::{CanonicalQueryInput, CanonicalVarValues};
-use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableValue, ConstVidKey};
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::traits::select;
 pub use rustc_middle::ty::IntVarValue;
@@ -46,6 +45,7 @@ use tracing::{debug, instrument};
 use type_variable::TypeVariableOrigin;
 
 use crate::infer::region_constraints::UndoLog;
+use crate::infer::unify_key::{ConstVariableOrigin, ConstVariableValue, ConstVidKey};
 use crate::traits::{
     self, ObligationCause, ObligationInspector, PredicateObligations, TraitEngine,
 };
@@ -64,6 +64,7 @@ pub mod relate;
 pub mod resolve;
 pub(crate) mod snapshot;
 mod type_variable;
+mod unify_key;
 
 /// `InferOk<'tcx, ()>` is used a lot. It may seem like a useless wrapper
 /// around `PredicateObligations<'tcx>`, but it has one important property:

compiler/rustc_infer/src/infer/region_constraints/mod.rs

@@ -8,7 +8,6 @@ use rustc_data_structures::undo_log::UndoLogs;
 use rustc_data_structures::unify as ut;
 use rustc_index::IndexVec;
 use rustc_macros::{TypeFoldable, TypeVisitable};
-use rustc_middle::infer::unify_key::{RegionVariableValue, RegionVidKey};
 use rustc_middle::ty::{self, ReBound, ReStatic, ReVar, Region, RegionVid, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
 use tracing::{debug, instrument};
@@ -17,6 +16,7 @@ use self::CombineMapType::*;
 use self::UndoLog::*;
 use super::{MiscVariable, RegionVariableOrigin, Rollback, SubregionOrigin};
 use crate::infer::snapshot::undo_log::{InferCtxtUndoLogs, Snapshot};
+use crate::infer::unify_key::{RegionVariableValue, RegionVidKey};
 
 mod leak_check;
 

compiler/rustc_infer/src/infer/relate/generalize.rs

@@ -4,7 +4,6 @@ use rustc_data_structures::sso::SsoHashMap;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir::def_id::DefId;
 use rustc_middle::bug;
-use rustc_middle::infer::unify_key::ConstVariableValue;
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::visit::MaxUniverse;
 use rustc_middle::ty::{
@@ -18,6 +17,7 @@ use super::{
     PredicateEmittingRelation, Relate, RelateResult, StructurallyRelateAliases, TypeRelation,
 };
 use crate::infer::type_variable::TypeVariableValue;
+use crate::infer::unify_key::ConstVariableValue;
 use crate::infer::{InferCtxt, RegionVariableOrigin, relate};
 
 impl<'tcx> InferCtxt<'tcx> {

compiler/rustc_infer/src/infer/snapshot/fudge.rs

@@ -1,7 +1,6 @@
 use std::ops::Range;
 
 use rustc_data_structures::{snapshot_vec as sv, unify as ut};
-use rustc_middle::infer::unify_key::{ConstVariableValue, ConstVidKey};
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::{self, ConstVid, FloatVid, IntVid, RegionVid, Ty, TyCtxt, TyVid};
 use rustc_type_ir::visit::TypeVisitableExt;
@@ -10,6 +9,7 @@ use ut::UnifyKey;
 
 use super::VariableLengths;
 use crate::infer::type_variable::TypeVariableOrigin;
+use crate::infer::unify_key::{ConstVariableValue, ConstVidKey};
 use crate::infer::{ConstVariableOrigin, InferCtxt, RegionVariableOrigin, UnificationTable};
 
 fn vars_since_snapshot<'tcx, T>(

compiler/rustc_infer/src/infer/snapshot/undo_log.rs

@@ -2,10 +2,10 @@ use std::marker::PhantomData;
 
 use rustc_data_structures::undo_log::{Rollback, UndoLogs};
 use rustc_data_structures::{snapshot_vec as sv, unify as ut};
-use rustc_middle::infer::unify_key::{ConstVidKey, RegionVidKey};
 use rustc_middle::ty::{self, OpaqueHiddenType, OpaqueTypeKey};
 use tracing::debug;
 
+use crate::infer::unify_key::{ConstVidKey, RegionVidKey};
 use crate::infer::{InferCtxtInner, region_constraints, type_variable};
 use crate::traits;
 

compiler/rustc_infer/src/infer/unify_key.rs

@@ -2,19 +2,18 @@ use std::cmp;
 use std::marker::PhantomData;
 
 use rustc_data_structures::unify::{NoError, UnifyKey, UnifyValue};
+use rustc_middle::{bug, ty};
 use rustc_span::Span;
 use rustc_span::def_id::DefId;
 
-use crate::ty;
-
 #[derive(Copy, Clone, Debug)]
-pub enum RegionVariableValue<'tcx> {
+pub(crate) enum RegionVariableValue<'tcx> {
     Known { value: ty::Region<'tcx> },
     Unknown { universe: ty::UniverseIndex },
 }
 
 #[derive(PartialEq, Copy, Clone, Debug)]
-pub struct RegionVidKey<'tcx> {
+pub(crate) struct RegionVidKey<'tcx> {
     pub vid: ty::RegionVid,
     pub phantom: PhantomData<RegionVariableValue<'tcx>>,
 }
@@ -40,7 +39,8 @@ impl<'tcx> UnifyKey for RegionVidKey<'tcx> {
     }
 }
 
-pub struct RegionUnificationError;
+pub(crate) struct RegionUnificationError;
+
 impl<'tcx> UnifyValue for RegionVariableValue<'tcx> {
     type Error = RegionUnificationError;
 
@@ -96,7 +96,7 @@ pub struct ConstVariableOrigin {
 }
 
 #[derive(Copy, Clone, Debug)]
-pub enum ConstVariableValue<'tcx> {
+pub(crate) enum ConstVariableValue<'tcx> {
     Known { value: ty::Const<'tcx> },
     Unknown { origin: ConstVariableOrigin, universe: ty::UniverseIndex },
 }
@@ -104,7 +104,7 @@ pub enum ConstVariableValue<'tcx> {
 impl<'tcx> ConstVariableValue<'tcx> {
     /// If this value is known, returns the const it is known to be.
     /// Otherwise, `None`.
-    pub fn known(&self) -> Option<ty::Const<'tcx>> {
+    pub(crate) fn known(&self) -> Option<ty::Const<'tcx>> {
         match *self {
             ConstVariableValue::Unknown { .. } => None,
             ConstVariableValue::Known { value } => Some(value),
@@ -113,7 +113,7 @@ impl<'tcx> ConstVariableValue<'tcx> {
 }
 
 #[derive(PartialEq, Copy, Clone, Debug)]
-pub struct ConstVidKey<'tcx> {
+pub(crate) struct ConstVidKey<'tcx> {
     pub vid: ty::ConstVid,
     pub phantom: PhantomData<ty::Const<'tcx>>,
 }

compiler/rustc_middle/src/infer/mod.rs

@@ -1,2 +1 @@
 pub mod canonical;
-pub mod unify_key;