diff --git a/compiler/rustc_middle/src/infer/canonical.rs b/compiler/rustc_middle/src/infer/canonical.rs
index 2247090c38c..6e130bbf7d8 100644
--- a/compiler/rustc_middle/src/infer/canonical.rs
+++ b/compiler/rustc_middle/src/infer/canonical.rs
@@ -337,6 +337,39 @@ TrivialTypeTraversalAndLiftImpls! {
 }
 
 impl<'tcx> CanonicalVarValues<'tcx> {
+    // Given a list of canonical variables, construct a set of values which are
+    // the identity response.
+    pub fn make_identity(
+        tcx: TyCtxt<'tcx>,
+        infos: CanonicalVarInfos<'tcx>,
+    ) -> CanonicalVarValues<'tcx> {
+        CanonicalVarValues {
+            var_values: tcx.mk_substs(infos.iter().enumerate().map(
+                |(i, info)| -> ty::GenericArg<'tcx> {
+                    match info.kind {
+                        CanonicalVarKind::Ty(_) | CanonicalVarKind::PlaceholderTy(_) => tcx
+                            .mk_ty(ty::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i).into()))
+                            .into(),
+                        CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => {
+                            let br = ty::BoundRegion {
+                                var: ty::BoundVar::from_usize(i),
+                                kind: ty::BrAnon(i as u32, None),
+                            };
+                            tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br)).into()
+                        }
+                        CanonicalVarKind::Const(_, ty)
+                        | CanonicalVarKind::PlaceholderConst(_, ty) => tcx
+                            .mk_const(
+                                ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i)),
+                                ty,
+                            )
+                            .into(),
+                    }
+                },
+            )),
+        }
+    }
+
     /// Creates dummy var values which should not be used in a
     /// canonical response.
     pub fn dummy() -> CanonicalVarValues<'tcx> {
@@ -347,41 +380,6 @@ impl<'tcx> CanonicalVarValues<'tcx> {
     pub fn len(&self) -> usize {
         self.var_values.len()
     }
-
-    /// Makes an identity substitution from this one: each bound var
-    /// is matched to the same bound var, preserving the original kinds.
-    /// For example, if we have:
-    /// `self.var_values == [Type(u32), Lifetime('a), Type(u64)]`
-    /// we'll return a substitution `subst` with:
-    /// `subst.var_values == [Type(^0), Lifetime(^1), Type(^2)]`.
-    pub fn make_identity(&self, tcx: TyCtxt<'tcx>) -> Self {
-        use crate::ty::subst::GenericArgKind;
-
-        CanonicalVarValues {
-            var_values: tcx.mk_substs(self.var_values.iter().enumerate().map(
-                |(i, kind)| -> ty::GenericArg<'tcx> {
-                    match kind.unpack() {
-                        GenericArgKind::Type(..) => tcx
-                            .mk_ty(ty::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i).into()))
-                            .into(),
-                        GenericArgKind::Lifetime(..) => {
-                            let br = ty::BoundRegion {
-                                var: ty::BoundVar::from_usize(i),
-                                kind: ty::BrAnon(i as u32, None),
-                            };
-                            tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br)).into()
-                        }
-                        GenericArgKind::Const(ct) => tcx
-                            .mk_const(
-                                ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i)),
-                                ct.ty(),
-                            )
-                            .into(),
-                    }
-                },
-            )),
-        }
-    }
 }
 
 impl<'a, 'tcx> IntoIterator for &'a CanonicalVarValues<'tcx> {
diff --git a/compiler/rustc_trait_selection/src/solve/mod.rs b/compiler/rustc_trait_selection/src/solve/mod.rs
index 1bd2f0fbda9..cfb0dccd7b0 100644
--- a/compiler/rustc_trait_selection/src/solve/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/mod.rs
@@ -18,7 +18,7 @@
 use std::mem;
 
 use rustc_hir::def_id::DefId;
-use rustc_infer::infer::canonical::{Canonical, CanonicalVarKind, CanonicalVarValues};
+use rustc_infer::infer::canonical::{Canonical, CanonicalVarValues};
 use rustc_infer::infer::canonical::{OriginalQueryValues, QueryRegionConstraints, QueryResponse};
 use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
 use rustc_infer::traits::query::NoSolution;
@@ -481,30 +481,11 @@ pub(super) fn response_no_constraints<'tcx>(
     goal: Canonical<'tcx, impl Sized>,
     certainty: Certainty,
 ) -> QueryResult<'tcx> {
-    let var_values =
-        tcx.mk_substs(goal.variables.iter().enumerate().map(|(i, info)| -> ty::GenericArg<'tcx> {
-            match info.kind {
-                CanonicalVarKind::Ty(_) | CanonicalVarKind::PlaceholderTy(_) => {
-                    tcx.mk_ty(ty::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i).into())).into()
-                }
-                CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => {
-                    let br = ty::BoundRegion {
-                        var: ty::BoundVar::from_usize(i),
-                        kind: ty::BrAnon(i as u32, None),
-                    };
-                    tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br)).into()
-                }
-                CanonicalVarKind::Const(_, ty) | CanonicalVarKind::PlaceholderConst(_, ty) => tcx
-                    .mk_const(ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i)), ty)
-                    .into(),
-            }
-        }));
-
     Ok(Canonical {
         max_universe: goal.max_universe,
         variables: goal.variables,
         value: Response {
-            var_values: CanonicalVarValues { var_values },
+            var_values: CanonicalVarValues::make_identity(tcx, goal.variables),
             external_constraints: Default::default(),
             certainty,
         },