Move rustc_middle::MaxUniverse to rustc_infer.

Because `rust_infer` is the only crate that uses it.

Author: nnethercote

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

@@ -6,8 +6,8 @@ use rustc_hir::def_id::DefId;
 use rustc_middle::bug;
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::{
-    self, AliasRelationDirection, InferConst, MaxUniverse, Term, Ty, TyCtxt, TypeVisitable,
-    TypeVisitableExt, TypingMode,
+    self, AliasRelationDirection, InferConst, Term, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable,
+    TypeVisitableExt, TypeVisitor, TypingMode,
 };
 use rustc_span::Span;
 use tracing::{debug, instrument, warn};
@@ -290,6 +290,45 @@ impl<'tcx> InferCtxt<'tcx> {
     }
 }
 
+/// Finds the max universe present
+struct MaxUniverse {
+    max_universe: ty::UniverseIndex,
+}
+
+impl MaxUniverse {
+    fn new() -> Self {
+        MaxUniverse { max_universe: ty::UniverseIndex::ROOT }
+    }
+
+    fn max_universe(self) -> ty::UniverseIndex {
+        self.max_universe
+    }
+}
+
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
+    fn visit_ty(&mut self, t: Ty<'tcx>) {
+        if let ty::Placeholder(placeholder) = t.kind() {
+            self.max_universe = self.max_universe.max(placeholder.universe);
+        }
+
+        t.super_visit_with(self)
+    }
+
+    fn visit_const(&mut self, c: ty::Const<'tcx>) {
+        if let ty::ConstKind::Placeholder(placeholder) = c.kind() {
+            self.max_universe = self.max_universe.max(placeholder.universe);
+        }
+
+        c.super_visit_with(self)
+    }
+
+    fn visit_region(&mut self, r: ty::Region<'tcx>) {
+        if let ty::RePlaceholder(placeholder) = r.kind() {
+            self.max_universe = self.max_universe.max(placeholder.universe);
+        }
+    }
+}
+
 /// The "generalizer" is used when handling inference variables.
 ///
 /// The basic strategy for handling a constraint like `?A <: B` is to

compiler/rustc_middle/src/ty/mod.rs

@@ -109,7 +109,6 @@ pub use self::typeck_results::{
     CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, IsIdentity,
     Rust2024IncompatiblePatInfo, TypeckResults, UserType, UserTypeAnnotationIndex, UserTypeKind,
 };
-pub use self::visit::*;
 use crate::error::{OpaqueHiddenTypeMismatch, TypeMismatchReason};
 use crate::metadata::ModChild;
 use crate::middle::privacy::EffectiveVisibilities;

compiler/rustc_middle/src/ty/visit.rs

@@ -212,42 +212,3 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for LateBoundRegionsCollector {
         }
     }
 }
-
-/// Finds the max universe present
-pub struct MaxUniverse {
-    max_universe: ty::UniverseIndex,
-}
-
-impl MaxUniverse {
-    pub fn new() -> Self {
-        MaxUniverse { max_universe: ty::UniverseIndex::ROOT }
-    }
-
-    pub fn max_universe(self) -> ty::UniverseIndex {
-        self.max_universe
-    }
-}
-
-impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MaxUniverse {
-    fn visit_ty(&mut self, t: Ty<'tcx>) {
-        if let ty::Placeholder(placeholder) = t.kind() {
-            self.max_universe = self.max_universe.max(placeholder.universe);
-        }
-
-        t.super_visit_with(self)
-    }
-
-    fn visit_const(&mut self, c: ty::consts::Const<'tcx>) {
-        if let ty::ConstKind::Placeholder(placeholder) = c.kind() {
-            self.max_universe = self.max_universe.max(placeholder.universe);
-        }
-
-        c.super_visit_with(self)
-    }
-
-    fn visit_region(&mut self, r: ty::Region<'tcx>) {
-        if let ty::RePlaceholder(placeholder) = r.kind() {
-            self.max_universe = self.max_universe.max(placeholder.universe);
-        }
-    }
-}