diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
index 57741a762b52..18ef51de3eaf 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -494,7 +494,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
 
         def hardenTypeVars(tp2: Type): Unit = tp2.dealiasKeepRefiningAnnots match
           case tvar: TypeVar if constraint.contains(tvar.origin) =>
-            state.rigidVars += tvar
+            state.hardVars += tvar
           case tp2: TypeParamRef if constraint.contains(tp2) =>
             hardenTypeVars(constraint.typeVarOfParam(tp2))
           case tp2: AndOrType =>
diff --git a/compiler/src/dotty/tools/dotc/core/TyperState.scala b/compiler/src/dotty/tools/dotc/core/TyperState.scala
index 01d5771b8f9b..a00836bf78c5 100644
--- a/compiler/src/dotty/tools/dotc/core/TyperState.scala
+++ b/compiler/src/dotty/tools/dotc/core/TyperState.scala
@@ -29,7 +29,7 @@ object TyperState {
     def snapshot()(using Context): Snapshot =
       var previouslyInstantiated: TypeVars = SimpleIdentitySet.empty
       for tv <- ts.ownedVars do if tv.inst.exists then previouslyInstantiated += tv
-      (ts.constraint, ts.ownedVars, previouslyInstantiated, ts.rigidVars)
+      (ts.constraint, ts.ownedVars, previouslyInstantiated, ts.hardVars)
 
     def resetTo(state: Snapshot)(using Context): Unit =
       val (c, tvs, previouslyInstantiated, rvars) = state
@@ -38,7 +38,7 @@ object TyperState {
           tv.resetInst(ts)
       ts.ownedVars = tvs
       ts.constraint = c
-      ts.rigidVars = rvars
+      ts.hardVars = rvars
 }
 
 class TyperState() {
@@ -94,9 +94,9 @@ class TyperState() {
    *  its lower bound, top-level soft unions in the instance type are converted
    *  to hard unions instead of being widened in `widenOr`.
    */
-  private var myRigidVars: TypeVars = _
-  def rigidVars: TypeVars = myRigidVars
-  def rigidVars_=(tvs: TypeVars): Unit = myRigidVars = tvs
+  private var myHardVars: TypeVars = _
+  def hardVars: TypeVars = myHardVars
+  def hardVars_=(tvs: TypeVars): Unit = myHardVars = tvs
 
   /** Initializes all fields except reporter, isCommittable, which need to be
    *  set separately.
@@ -108,7 +108,7 @@ class TyperState() {
     this.myConstraint = constraint
     this.previousConstraint = constraint
     this.myOwnedVars = SimpleIdentitySet.empty
-    this.myRigidVars = SimpleIdentitySet.empty
+    this.myHardVars = SimpleIdentitySet.empty
     this.isCommitted = false
     this
 
@@ -119,7 +119,7 @@ class TyperState() {
     val ts = TyperState().init(this, this.constraint)
       .setReporter(reporter)
       .setCommittable(committable)
-    ts.rigidVars = this.rigidVars
+    ts.hardVars = this.hardVars
     ts
 
   /** The uninstantiated variables */
@@ -173,7 +173,7 @@ class TyperState() {
       constr.println(i"committing $this to $targetState, fromConstr = $constraint, toConstr = ${targetState.constraint}")
       if targetState.constraint eq previousConstraint then
         targetState.constraint = constraint
-        targetState.rigidVars = rigidVars
+        targetState.hardVars = hardVars
         if !ownedVars.isEmpty then ownedVars.foreach(targetState.includeVar)
       else
         targetState.mergeConstraintWith(this)
@@ -226,7 +226,7 @@ class TyperState() {
           val otherLos = other.lower(p)
           val otherHis = other.upper(p)
           val otherEntry = other.entry(p)
-          if that.rigidVars.contains(tv) then this.myRigidVars += tv
+          if that.hardVars.contains(tv) then this.myHardVars += tv
           (  (otherLos eq constraint.lower(p)) || otherLos.forall(_ <:< p)) &&
           (  (otherHis eq constraint.upper(p)) || otherHis.forall(p <:< _)) &&
           ((otherEntry eq constraint.entry(p)) || otherEntry.match
diff --git a/compiler/src/dotty/tools/dotc/core/Types.scala b/compiler/src/dotty/tools/dotc/core/Types.scala
index 8191d29903c3..4dbfee72b366 100644
--- a/compiler/src/dotty/tools/dotc/core/Types.scala
+++ b/compiler/src/dotty/tools/dotc/core/Types.scala
@@ -4576,7 +4576,7 @@ object Types {
         instantiateWith(tp)
 
     def widenUnions(using Context) =
-      !ctx.typerState.rigidVars.contains(this)
+      !ctx.typerState.hardVars.contains(this)
 
     /** For uninstantiated type variables: the entry in the constraint (either bounds or
      *  provisional instance value)