diff --git a/compiler/src/dotty/tools/dotc/core/Definitions.scala b/compiler/src/dotty/tools/dotc/core/Definitions.scala
index 0bbd62123195..8263bab70aca 100644
--- a/compiler/src/dotty/tools/dotc/core/Definitions.scala
+++ b/compiler/src/dotty/tools/dotc/core/Definitions.scala
@@ -1104,8 +1104,6 @@ class Definitions {
   @tu lazy val AbstractFunctionType: Array[TypeRef] = mkArityArray("scala.runtime.AbstractFunction", MaxImplementedFunctionArity, 0)
   val AbstractFunctionClassPerRun: PerRun[Array[Symbol]] = new PerRun(AbstractFunctionType.map(_.symbol.asClass))
   def AbstractFunctionClass(n: Int)(using Context): Symbol = AbstractFunctionClassPerRun()(using ctx)(n)
-  @tu private lazy val ImplementedFunctionType = mkArityArray("scala.Function", MaxImplementedFunctionArity, 0)
-  def FunctionClassPerRun: PerRun[Array[Symbol]] = new PerRun(ImplementedFunctionType.map(_.symbol.asClass))
 
   val LazyHolder: PerRun[Map[Symbol, Symbol]] = new PerRun({
     def holderImpl(holderType: String) = requiredClass("scala.runtime." + holderType)
@@ -1124,23 +1122,33 @@ class Definitions {
 
   @tu lazy val TupleType: Array[TypeRef] = mkArityArray("scala.Tuple", MaxTupleArity, 1)
 
+  private class FunType(prefix: String):
+    private var classRefs: Array[TypeRef] = new Array(22)
+    def apply(n: Int): TypeRef =
+      while n >= classRefs.length do
+        val classRefs1 = new Array[TypeRef](classRefs.length * 2)
+        Array.copy(classRefs, 0, classRefs1, 0, classRefs.length)
+        classRefs = classRefs1
+      if classRefs(n) == null then
+        classRefs(n) = requiredClassRef(prefix + n.toString)
+      classRefs(n)
+
+  private val erasedContextFunType = FunType("scala.ErasedContextFunction")
+  private val contextFunType = FunType("scala.ContextFunction")
+  private val erasedFunType = FunType("scala.ErasedFunction")
+  private val funType = FunType("scala.Function")
+
   def FunctionClass(n: Int, isContextual: Boolean = false, isErased: Boolean = false)(using Context): Symbol =
-    if (isContextual && isErased)
-      requiredClass("scala.ErasedContextFunction" + n.toString)
-    else if (isContextual)
-      requiredClass("scala.ContextFunction" + n.toString)
-    else if (isErased)
-      requiredClass("scala.ErasedFunction" + n.toString)
-    else if (n <= MaxImplementedFunctionArity)
-      FunctionClassPerRun()(n)
-    else
-      requiredClass("scala.Function" + n.toString)
-
-  @tu lazy val Function0_apply: Symbol = ImplementedFunctionType(0).symbol.requiredMethod(nme.apply)
+    ( if isContextual && isErased then erasedContextFunType(n)
+      else if isContextual then contextFunType(n)
+      else if isErased then erasedFunType(n)
+      else funType(n)
+    ).symbol.asClass
+
+  @tu lazy val Function0_apply: Symbol = FunctionClass(0).requiredMethod(nme.apply)
 
   def FunctionType(n: Int, isContextual: Boolean = false, isErased: Boolean = false)(using Context): TypeRef =
-    if (n <= MaxImplementedFunctionArity && (!isContextual || ctx.erasedTypes) && !isErased) ImplementedFunctionType(n)
-    else FunctionClass(n, isContextual, isErased).typeRef
+    FunctionClass(n, isContextual && !ctx.erasedTypes, isErased).typeRef
 
   lazy val PolyFunctionClass = requiredClass("scala.PolyFunction")
   def PolyFunctionType = PolyFunctionClass.typeRef
diff --git a/compiler/src/dotty/tools/dotc/core/Names.scala b/compiler/src/dotty/tools/dotc/core/Names.scala
index d5e538abeac0..fea9edd18fa4 100644
--- a/compiler/src/dotty/tools/dotc/core/Names.scala
+++ b/compiler/src/dotty/tools/dotc/core/Names.scala
@@ -258,6 +258,15 @@ object Names {
       val (first, last, sep) = split
       if (first.isEmpty) f2(last) else str.sanitize(f1(first) + sep + f2(last))
     }
+
+    protected def computeToString: String
+
+    @sharable private var myToString: String = null
+
+    override def toString =
+      if myToString == null then myToString = computeToString
+      myToString
+
   }
 
   /** A simple name is essentially an interned string */
@@ -371,7 +380,7 @@ object Names {
 
     override def hashCode: Int = start
 
-    override def toString: String =
+    protected def computeToString: String =
       if (length == 0) ""
       else {
         if (Config.checkBackendNames)
@@ -500,7 +509,7 @@ object Names {
       case qual: QualifiedInfo => qual.name
       case _ => underlying.lastPart
     }
-    override def toString: String = info.mkString(underlying)
+    protected def computeToString: String = info.mkString(underlying)
     override def debugString: String = s"${underlying.debugString}[$info]"
   }
 
diff --git a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
index 6416c38d007a..7f7edb35495a 100644
--- a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
@@ -219,10 +219,7 @@ object SymbolLoaders {
     Stats.record("package scopes")
 
     /** The scope of a package. This is different from a normal scope
-  	 *  in two aspects:
-	   *
-	   *   1. Names of scope entries are kept in mangled form.
-	   *   2. Some function types in the `scala` package are synthesized.
+  	 *  in that names of scope entries are kept in mangled form.
   	 */
     final class PackageScope extends MutableScope {
       override def newScopeEntry(name: Name, sym: Symbol)(using Context): ScopeEntry =
diff --git a/tests/pos-with-compiler/lazyValsSepComp.scala b/tests/pos-with-compiler/lazyValsSepComp.scala
index 31f1619fcc25..78edf31d4567 100644
--- a/tests/pos-with-compiler/lazyValsSepComp.scala
+++ b/tests/pos-with-compiler/lazyValsSepComp.scala
@@ -12,5 +12,5 @@ import dotty.tools.dotc.core.Contexts._
 object Foo {
   val definitions: Definitions = null
   def defn = definitions
-  def go = defn.FunctionClassPerRun
+  def go = defn.ScalaBoxedClasses
 }