diff --git a/Cargo.lock b/Cargo.lock
index d1889fb6861..afeb9faec09 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4168,6 +4168,7 @@ dependencies = [
  "rustc_index",
  "rustc_macros",
  "rustc_middle",
+ "rustc_next_trait_solver",
  "rustc_span",
  "rustc_target",
  "rustc_type_ir",
diff --git a/compiler/rustc_borrowck/src/type_check/relate_tys.rs b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
index b9a82046e59..02b9c2d48b1 100644
--- a/compiler/rustc_borrowck/src/type_check/relate_tys.rs
+++ b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
@@ -1,8 +1,9 @@
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::ErrorGuaranteed;
-use rustc_infer::infer::relate::{PredicateEmittingRelation, StructurallyRelateAliases};
-use rustc_infer::infer::relate::{Relate, RelateResult, TypeRelation};
-use rustc_infer::infer::NllRegionVariableOrigin;
+use rustc_infer::infer::relate::{
+    PredicateEmittingRelation, Relate, RelateResult, StructurallyRelateAliases, TypeRelation,
+};
+use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin};
 use rustc_infer::traits::solve::Goal;
 use rustc_infer::traits::Obligation;
 use rustc_middle::mir::ConstraintCategory;
@@ -522,7 +523,7 @@ impl<'bccx, 'tcx> TypeRelation<TyCtxt<'tcx>> for NllTypeRelating<'_, 'bccx, 'tcx
     }
 }
 
-impl<'bccx, 'tcx> PredicateEmittingRelation<'tcx> for NllTypeRelating<'_, 'bccx, 'tcx> {
+impl<'bccx, 'tcx> PredicateEmittingRelation<InferCtxt<'tcx>> for NllTypeRelating<'_, 'bccx, 'tcx> {
     fn span(&self) -> Span {
         self.locations.span(self.type_checker.body)
     }
diff --git a/compiler/rustc_infer/Cargo.toml b/compiler/rustc_infer/Cargo.toml
index 5136ab79a0f..1f616710200 100644
--- a/compiler/rustc_infer/Cargo.toml
+++ b/compiler/rustc_infer/Cargo.toml
@@ -16,6 +16,7 @@ rustc_hir = { path = "../rustc_hir" }
 rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_middle = { path = "../rustc_middle" }
+rustc_next_trait_solver = { path = "../rustc_next_trait_solver" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_type_ir = { path = "../rustc_type_ir" }
diff --git a/compiler/rustc_infer/src/infer/relate/combine.rs b/compiler/rustc_infer/src/infer/relate/combine.rs
index 0a2e85cc891..c93b89756f9 100644
--- a/compiler/rustc_infer/src/infer/relate/combine.rs
+++ b/compiler/rustc_infer/src/infer/relate/combine.rs
@@ -18,11 +18,13 @@
 //! On success, the  LUB/GLB operations return the appropriate bound. The
 //! return value of `Equate` or `Sub` shouldn't really be used.
 
+pub use rustc_next_trait_solver::relate::combine::*;
+
 use super::glb::Glb;
 use super::lub::Lub;
 use super::type_relating::TypeRelating;
+use super::RelateResult;
 use super::StructurallyRelateAliases;
-use super::{RelateResult, TypeRelation};
 use crate::infer::relate;
 use crate::infer::{DefineOpaqueTypes, InferCtxt, TypeTrace};
 use crate::traits::{Obligation, PredicateObligation};
@@ -32,7 +34,6 @@ use rustc_middle::traits::solve::Goal;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::{self, InferConst, Ty, TyCtxt, TypeVisitableExt, Upcast};
 use rustc_middle::ty::{IntType, UintType};
-use rustc_span::Span;
 
 #[derive(Clone)]
 pub struct CombineFields<'infcx, 'tcx> {
@@ -76,7 +77,7 @@ impl<'tcx> InferCtxt<'tcx> {
         b: Ty<'tcx>,
     ) -> RelateResult<'tcx, Ty<'tcx>>
     where
-        R: PredicateEmittingRelation<'tcx>,
+        R: PredicateEmittingRelation<InferCtxt<'tcx>>,
     {
         debug_assert!(!a.has_escaping_bound_vars());
         debug_assert!(!b.has_escaping_bound_vars());
@@ -171,7 +172,7 @@ impl<'tcx> InferCtxt<'tcx> {
         b: ty::Const<'tcx>,
     ) -> RelateResult<'tcx, ty::Const<'tcx>>
     where
-        R: PredicateEmittingRelation<'tcx>,
+        R: PredicateEmittingRelation<InferCtxt<'tcx>>,
     {
         debug!("{}.consts({:?}, {:?})", relation.tag(), a, b);
         debug_assert!(!a.has_escaping_bound_vars());
@@ -323,30 +324,3 @@ impl<'infcx, 'tcx> CombineFields<'infcx, 'tcx> {
         )
     }
 }
-
-pub trait PredicateEmittingRelation<'tcx>: TypeRelation<TyCtxt<'tcx>> {
-    fn span(&self) -> Span;
-
-    fn param_env(&self) -> ty::ParamEnv<'tcx>;
-
-    /// Whether aliases should be related structurally. This is pretty much
-    /// always `No` unless you're equating in some specific locations of the
-    /// new solver. See the comments in these use-cases for more details.
-    fn structurally_relate_aliases(&self) -> StructurallyRelateAliases;
-
-    /// Register obligations that must hold in order for this relation to hold
-    fn register_goals(
-        &mut self,
-        obligations: impl IntoIterator<Item = Goal<'tcx, ty::Predicate<'tcx>>>,
-    );
-
-    /// Register predicates that must hold in order for this relation to hold.
-    /// This uses the default `param_env` of the obligation.
-    fn register_predicates(
-        &mut self,
-        obligations: impl IntoIterator<Item: Upcast<TyCtxt<'tcx>, ty::Predicate<'tcx>>>,
-    );
-
-    /// Register `AliasRelate` obligation(s) that both types must be related to each other.
-    fn register_alias_relate_predicate(&mut self, a: Ty<'tcx>, b: Ty<'tcx>);
-}
diff --git a/compiler/rustc_infer/src/infer/relate/generalize.rs b/compiler/rustc_infer/src/infer/relate/generalize.rs
index d6e57d85387..fe3b8d60fb9 100644
--- a/compiler/rustc_infer/src/infer/relate/generalize.rs
+++ b/compiler/rustc_infer/src/infer/relate/generalize.rs
@@ -30,7 +30,7 @@ impl<'tcx> InferCtxt<'tcx> {
     /// `TypeRelation`. Do not use this, and instead please use `At::eq`, for all
     /// other usecases (i.e. setting the value of a type var).
     #[instrument(level = "debug", skip(self, relation))]
-    pub fn instantiate_ty_var<R: PredicateEmittingRelation<'tcx>>(
+    pub fn instantiate_ty_var<R: PredicateEmittingRelation<InferCtxt<'tcx>>>(
         &self,
         relation: &mut R,
         target_is_expected: bool,
@@ -178,7 +178,7 @@ impl<'tcx> InferCtxt<'tcx> {
     ///
     /// See `tests/ui/const-generics/occurs-check/` for more examples where this is relevant.
     #[instrument(level = "debug", skip(self, relation))]
-    pub(super) fn instantiate_const_var<R: PredicateEmittingRelation<'tcx>>(
+    pub(super) fn instantiate_const_var<R: PredicateEmittingRelation<InferCtxt<'tcx>>>(
         &self,
         relation: &mut R,
         target_is_expected: bool,
diff --git a/compiler/rustc_infer/src/infer/relate/glb.rs b/compiler/rustc_infer/src/infer/relate/glb.rs
index 067004ecaeb..5bb8a113e17 100644
--- a/compiler/rustc_infer/src/infer/relate/glb.rs
+++ b/compiler/rustc_infer/src/infer/relate/glb.rs
@@ -123,7 +123,7 @@ impl<'combine, 'infcx, 'tcx> LatticeDir<'infcx, 'tcx> for Glb<'combine, 'infcx,
     }
 }
 
-impl<'tcx> PredicateEmittingRelation<'tcx> for Glb<'_, '_, 'tcx> {
+impl<'tcx> PredicateEmittingRelation<InferCtxt<'tcx>> for Glb<'_, '_, 'tcx> {
     fn span(&self) -> Span {
         self.fields.trace.span()
     }
diff --git a/compiler/rustc_infer/src/infer/relate/lattice.rs b/compiler/rustc_infer/src/infer/relate/lattice.rs
index 6cc8d6d910a..46e7466141a 100644
--- a/compiler/rustc_infer/src/infer/relate/lattice.rs
+++ b/compiler/rustc_infer/src/infer/relate/lattice.rs
@@ -30,7 +30,7 @@ use rustc_middle::ty::{self, Ty};
 ///
 /// GLB moves "down" the lattice (to smaller values); LUB moves
 /// "up" the lattice (to bigger values).
-pub trait LatticeDir<'f, 'tcx>: PredicateEmittingRelation<'tcx> {
+pub trait LatticeDir<'f, 'tcx>: PredicateEmittingRelation<InferCtxt<'tcx>> {
     fn infcx(&self) -> &'f InferCtxt<'tcx>;
 
     fn cause(&self) -> &ObligationCause<'tcx>;
diff --git a/compiler/rustc_infer/src/infer/relate/lub.rs b/compiler/rustc_infer/src/infer/relate/lub.rs
index 2184416b4cc..94c1464817f 100644
--- a/compiler/rustc_infer/src/infer/relate/lub.rs
+++ b/compiler/rustc_infer/src/infer/relate/lub.rs
@@ -123,7 +123,7 @@ impl<'combine, 'infcx, 'tcx> LatticeDir<'infcx, 'tcx> for Lub<'combine, 'infcx,
     }
 }
 
-impl<'tcx> PredicateEmittingRelation<'tcx> for Lub<'_, '_, 'tcx> {
+impl<'tcx> PredicateEmittingRelation<InferCtxt<'tcx>> for Lub<'_, '_, 'tcx> {
     fn span(&self) -> Span {
         self.fields.trace.span()
     }
diff --git a/compiler/rustc_infer/src/infer/relate/mod.rs b/compiler/rustc_infer/src/infer/relate/mod.rs
index 41cc945492d..dd97dc061fe 100644
--- a/compiler/rustc_infer/src/infer/relate/mod.rs
+++ b/compiler/rustc_infer/src/infer/relate/mod.rs
@@ -2,11 +2,13 @@
 //! (except for some relations used for diagnostics and heuristics in the compiler).
 //! As well as the implementation of `Relate` for interned things (`Ty`/`Const`/etc).
 
-pub use rustc_middle::ty::relate::*;
+pub use rustc_middle::ty::relate::RelateResult;
+pub use rustc_next_trait_solver::relate::*;
 
 pub use self::combine::CombineFields;
 pub use self::combine::PredicateEmittingRelation;
 
+#[allow(hidden_glob_reexports)]
 pub(super) mod combine;
 mod generalize;
 mod glb;
diff --git a/compiler/rustc_infer/src/infer/relate/type_relating.rs b/compiler/rustc_infer/src/infer/relate/type_relating.rs
index f2bec9392d5..e206f530519 100644
--- a/compiler/rustc_infer/src/infer/relate/type_relating.rs
+++ b/compiler/rustc_infer/src/infer/relate/type_relating.rs
@@ -1,7 +1,7 @@
 use super::combine::CombineFields;
 use crate::infer::relate::{PredicateEmittingRelation, StructurallyRelateAliases};
 use crate::infer::BoundRegionConversionTime::HigherRankedType;
-use crate::infer::{DefineOpaqueTypes, SubregionOrigin};
+use crate::infer::{DefineOpaqueTypes, InferCtxt, SubregionOrigin};
 use rustc_middle::traits::solve::Goal;
 use rustc_middle::ty::relate::{
     relate_args_invariantly, relate_args_with_variances, Relate, RelateResult, TypeRelation,
@@ -296,7 +296,7 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for TypeRelating<'_, '_, 'tcx> {
     }
 }
 
-impl<'tcx> PredicateEmittingRelation<'tcx> for TypeRelating<'_, '_, 'tcx> {
+impl<'tcx> PredicateEmittingRelation<InferCtxt<'tcx>> for TypeRelating<'_, '_, 'tcx> {
     fn span(&self) -> Span {
         self.fields.trace.span()
     }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 055749ba3a3..dca48069974 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -92,6 +92,8 @@ use std::ops::{Bound, Deref};
 impl<'tcx> Interner for TyCtxt<'tcx> {
     type DefId = DefId;
     type LocalDefId = LocalDefId;
+    type Span = Span;
+
     type GenericArgs = ty::GenericArgsRef<'tcx>;
 
     type GenericArgsSlice = &'tcx [ty::GenericArg<'tcx>];
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index b169d672a84..ebf0d7ed737 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -10,18 +10,6 @@ use crate::ty::{self as ty, Ty, TyCtxt};
 
 pub type RelateResult<'tcx, T> = rustc_type_ir::relate::RelateResult<TyCtxt<'tcx>, T>;
 
-/// Whether aliases should be related structurally or not. Used
-/// to adjust the behavior of generalization and combine.
-///
-/// This should always be `No` unless in a few special-cases when
-/// instantiating canonical responses and in the new solver. Each
-/// such case should have a comment explaining why it is used.
-#[derive(Debug, Copy, Clone)]
-pub enum StructurallyRelateAliases {
-    Yes,
-    No,
-}
-
 impl<'tcx> Relate<TyCtxt<'tcx>> for ty::ImplSubject<'tcx> {
     #[inline]
     fn relate<R: TypeRelation<TyCtxt<'tcx>>>(
diff --git a/compiler/rustc_next_trait_solver/src/lib.rs b/compiler/rustc_next_trait_solver/src/lib.rs
index a6a9c01faaa..761475d3d6b 100644
--- a/compiler/rustc_next_trait_solver/src/lib.rs
+++ b/compiler/rustc_next_trait_solver/src/lib.rs
@@ -6,5 +6,6 @@
 
 pub mod canonicalizer;
 pub mod delegate;
+pub mod relate;
 pub mod resolve;
 pub mod solve;
diff --git a/compiler/rustc_next_trait_solver/src/relate.rs b/compiler/rustc_next_trait_solver/src/relate.rs
new file mode 100644
index 00000000000..db819961bbd
--- /dev/null
+++ b/compiler/rustc_next_trait_solver/src/relate.rs
@@ -0,0 +1,15 @@
+pub use rustc_type_ir::relate::*;
+
+pub mod combine;
+
+/// Whether aliases should be related structurally or not. Used
+/// to adjust the behavior of generalization and combine.
+///
+/// This should always be `No` unless in a few special-cases when
+/// instantiating canonical responses and in the new solver. Each
+/// such case should have a comment explaining why it is used.
+#[derive(Debug, Copy, Clone)]
+pub enum StructurallyRelateAliases {
+    Yes,
+    No,
+}
diff --git a/compiler/rustc_next_trait_solver/src/relate/combine.rs b/compiler/rustc_next_trait_solver/src/relate/combine.rs
new file mode 100644
index 00000000000..96968327d8e
--- /dev/null
+++ b/compiler/rustc_next_trait_solver/src/relate/combine.rs
@@ -0,0 +1,34 @@
+pub use rustc_type_ir::relate::*;
+use rustc_type_ir::solve::Goal;
+use rustc_type_ir::{InferCtxtLike, Interner, Upcast};
+
+use super::StructurallyRelateAliases;
+
+pub trait PredicateEmittingRelation<Infcx, I = <Infcx as InferCtxtLike>::Interner>:
+    TypeRelation<I>
+where
+    Infcx: InferCtxtLike<Interner = I>,
+    I: Interner,
+{
+    fn span(&self) -> I::Span;
+
+    fn param_env(&self) -> I::ParamEnv;
+
+    /// Whether aliases should be related structurally. This is pretty much
+    /// always `No` unless you're equating in some specific locations of the
+    /// new solver. See the comments in these use-cases for more details.
+    fn structurally_relate_aliases(&self) -> StructurallyRelateAliases;
+
+    /// Register obligations that must hold in order for this relation to hold
+    fn register_goals(&mut self, obligations: impl IntoIterator<Item = Goal<I, I::Predicate>>);
+
+    /// Register predicates that must hold in order for this relation to hold.
+    /// This uses the default `param_env` of the obligation.
+    fn register_predicates(
+        &mut self,
+        obligations: impl IntoIterator<Item: Upcast<I, I::Predicate>>,
+    );
+
+    /// Register `AliasRelate` obligation(s) that both types must be related to each other.
+    fn register_alias_relate_predicate(&mut self, a: I::Ty, b: I::Ty);
+}
diff --git a/compiler/rustc_type_ir/src/interner.rs b/compiler/rustc_type_ir/src/interner.rs
index db97bdca382..646939d8475 100644
--- a/compiler/rustc_type_ir/src/interner.rs
+++ b/compiler/rustc_type_ir/src/interner.rs
@@ -32,6 +32,7 @@ pub trait Interner:
 {
     type DefId: DefId<Self>;
     type LocalDefId: Copy + Debug + Hash + Eq + Into<Self::DefId> + TypeFoldable<Self>;
+    type Span: Copy + Debug + Hash + Eq;
 
     type GenericArgs: GenericArgs<Self>;
     type GenericArgsSlice: Copy + Debug + Hash + Eq + SliceLike<Item = Self::GenericArg>;