diff --git a/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala b/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
index 9a4b53d4112c..f94ff68d0698 100644
--- a/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
+++ b/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
@@ -3,6 +3,7 @@ package dotc
 package printing
 
 import core._
+import Constants.*
 import Texts._
 import Types._
 import Flags._
@@ -286,14 +287,10 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
       case tp: ViewProto =>
         toText(tp.argType) ~ " ?=>? " ~ toText(tp.resultType)
       case tp @ FunProto(args, resultType) =>
-        val argsText = args match {
-          case dummyTreeOfType(tp) :: Nil if !(tp isRef defn.NullClass) => "null: " ~ toText(tp)
-          case _ => toTextGlobal(args, ", ")
-        }
         "[applied to ("
         ~ keywordText("using ").provided(tp.isContextualMethod)
         ~ keywordText("erased ").provided(tp.isErasedMethod)
-        ~ argsText
+        ~ argsTreeText(args)
         ~ ") returning "
         ~ toText(resultType)
         ~ "]"
@@ -309,6 +306,10 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
   protected def exprToText(tp: ExprType): Text =
     "=> " ~ toText(tp.resType)
 
+  protected def argsTreeText(args: List[untpd.Tree]): Text = args match
+    case dummyTreeOfType(tp) :: Nil if !tp.isRef(defn.NullClass) && !homogenizedView => toText(Constant(null)) ~ ": " ~ toText(tp)
+    case _                                                                           => toTextGlobal(args, ", ")
+
   protected def blockToText[T <: Untyped](block: Block[T]): Text =
     blockText(block.stats :+ block.expr)
 
@@ -442,7 +443,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
           toTextLocal(fun)
           ~ "("
           ~ Str("using ").provided(app.applyKind == ApplyKind.Using && !homogenizedView)
-          ~ toTextGlobal(args, ", ")
+          ~ argsTreeText(args)
           ~ ")"
       case tree: TypeApply =>
         typeApplyText(tree)
diff --git a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
index 8ba842ad695f..15da3c2ccc22 100644
--- a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
+++ b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
@@ -671,10 +671,12 @@ object ProtoTypes {
    *
    *    [] _
    */
-  @sharable object AnyFunctionProto extends UncachedGroundType with MatchAlways
+  @sharable object AnyFunctionProto extends UncachedGroundType with MatchAlways:
+    override def toString = "AnyFunctionProto"
 
   /** A prototype for type constructors that are followed by a type application */
-  @sharable object AnyTypeConstructorProto extends UncachedGroundType with MatchAlways
+  @sharable object AnyTypeConstructorProto extends UncachedGroundType with MatchAlways:
+    override def toString = "AnyTypeConstructorProto"
 
   extension (pt: Type)
     def isExtensionApplyProto: Boolean = pt match
@@ -946,8 +948,8 @@ object ProtoTypes {
   object dummyTreeOfType {
     def apply(tp: Type)(implicit src: SourceFile): Tree =
       untpd.Literal(Constant(null)) withTypeUnchecked tp
-    def unapply(tree: untpd.Tree): Option[Type] = tree match {
-      case Literal(Constant(null)) => Some(tree.typeOpt)
+    def unapply(tree: untpd.Tree): Option[Type] = untpd.unsplice(tree) match {
+      case tree @ Literal(Constant(null)) => Some(tree.typeOpt)
       case _ => None
     }
   }