diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs
index 96a398ddf05..e424a51d01c 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -153,7 +153,7 @@ where
         tcx: TyCtxt<'tcx>,
         ct: AbstractConst<'tcx>,
     ) -> ControlFlow<V::BreakTy> {
-        const_evaluatable::walk_abstract_const(tcx, ct, |node| match node.root(tcx, ct.substs) {
+        const_evaluatable::walk_abstract_const(tcx, ct, |node| match node.root(tcx) {
             ACNode::Leaf(leaf) => self.visit_const(leaf),
             ACNode::Cast(_, _, ty) => self.visit_ty(ty),
             ACNode::Binop(..) | ACNode::UnaryOp(..) | ACNode::FunctionCall(_, _) => {
diff --git a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
index 5f7a9a17e03..1adcda41102 100644
--- a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
+++ b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
@@ -16,7 +16,7 @@ use rustc_infer::infer::InferCtxt;
 use rustc_middle::mir::abstract_const::{Node, NodeId, NotConstEvaluatable};
 use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::mir::{self, Rvalue, StatementKind, TerminatorKind};
-use rustc_middle::ty::subst::{GenericArg, Subst, SubstsRef};
+use rustc_middle::ty::subst::{Subst, SubstsRef};
 use rustc_middle::ty::{self, TyCtxt, TypeFoldable};
 use rustc_session::lint;
 use rustc_span::def_id::LocalDefId;
@@ -80,7 +80,7 @@ pub fn is_const_evaluatable<'cx, 'tcx>(
                     Concrete,
                 }
                 let mut failure_kind = FailureKind::Concrete;
-                walk_abstract_const::<!, _>(tcx, ct, |node| match node.root(tcx, ct.substs) {
+                walk_abstract_const::<!, _>(tcx, ct, |node| match node.root(tcx) {
                     Node::Leaf(leaf) => {
                         if leaf.has_infer_types_or_consts() {
                             failure_kind = FailureKind::MentionsInfer;
@@ -185,8 +185,8 @@ pub fn is_const_evaluatable<'cx, 'tcx>(
 pub struct AbstractConst<'tcx> {
     // FIXME: Consider adding something like `IndexSlice`
     // and use this here.
-    pub inner: &'tcx [Node<'tcx>],
-    pub substs: SubstsRef<'tcx>,
+    inner: &'tcx [Node<'tcx>],
+    substs: SubstsRef<'tcx>,
 }
 
 impl<'tcx> AbstractConst<'tcx> {
@@ -216,10 +216,10 @@ impl<'tcx> AbstractConst<'tcx> {
     }
 
     #[inline]
-    pub fn root(self, tcx: TyCtxt<'tcx>, substs: &[GenericArg<'tcx>]) -> Node<'tcx> {
-        let mut node = self.inner.last().copied().unwrap();
+    pub fn root(self, tcx: TyCtxt<'tcx>) -> Node<'tcx> {
+        let node = self.inner.last().copied().unwrap();
         if let Node::Leaf(leaf) = node {
-            node = Node::Leaf(leaf.subst(tcx, substs));
+            return Node::Leaf(leaf.subst(tcx, self.substs));
         }
         node
     }
@@ -589,7 +589,7 @@ where
         f: &mut dyn FnMut(AbstractConst<'tcx>) -> ControlFlow<R>,
     ) -> ControlFlow<R> {
         f(ct)?;
-        let root = ct.root(tcx, ct.substs);
+        let root = ct.root(tcx);
         match root {
             Node::Leaf(_) => ControlFlow::CONTINUE,
             Node::Binop(_, l, r) => {
@@ -617,14 +617,14 @@ pub(super) fn try_unify<'tcx>(
     // We substitute generics repeatedly to allow AbstractConsts to unify where a
     // ConstKind::Unevalated could be turned into an AbstractConst that would unify e.g.
     // Param(N) should unify with Param(T), substs: [Unevaluated("T2", [Unevaluated("T3", [Param(N)])])]
-    while let Node::Leaf(a_ct) = a.root(tcx, a.substs) {
+    while let Node::Leaf(a_ct) = a.root(tcx) {
         match AbstractConst::from_const(tcx, a_ct) {
             Ok(Some(a_act)) => a = a_act,
             Ok(None) => break,
             Err(_) => return true,
         }
     }
-    while let Node::Leaf(b_ct) = b.root(tcx, b.substs) {
+    while let Node::Leaf(b_ct) = b.root(tcx) {
         match AbstractConst::from_const(tcx, b_ct) {
             Ok(Some(b_act)) => b = b_act,
             Ok(None) => break,
@@ -632,7 +632,7 @@ pub(super) fn try_unify<'tcx>(
         }
     }
 
-    match (a.root(tcx, a.substs), b.root(tcx, b.substs)) {
+    match (a.root(tcx), b.root(tcx)) {
         (Node::Leaf(a_ct), Node::Leaf(b_ct)) => {
             if a_ct.ty != b_ct.ty {
                 return false;
diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs
index 6c60394116b..4eaa3ea4732 100644
--- a/compiler/rustc_trait_selection/src/traits/object_safety.rs
+++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs
@@ -839,7 +839,7 @@ fn contains_illegal_self_type_reference<'tcx, T: TypeFoldable<'tcx>>(
             use rustc_middle::mir::abstract_const::Node;
             if let Ok(Some(ct)) = AbstractConst::new(self.tcx, uv.shrink()) {
                 const_evaluatable::walk_abstract_const(self.tcx, ct, |node| {
-                    match node.root(self.tcx, ct.substs) {
+                    match node.root(self.tcx) {
                         Node::Leaf(leaf) => self.visit_const(leaf),
                         Node::Cast(_, _, ty) => self.visit_ty(ty),
                         Node::Binop(..) | Node::UnaryOp(..) | Node::FunctionCall(_, _) => {