remove ExportType sentinal

Author: bishabosha

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -4815,11 +4815,6 @@ object Types {
   /** The type of an import clause tree */
   case class ImportType(expr: Tree) extends UncachedGroundType
 
-  /** Sentinal for typed export clauses */
-  @sharable case object ExportType extends CachedGroundType {
-    override def computeHash(bs: Binders): Int = hashSeed
-  }
-
   /** Sentinel for "missing type" */
   @sharable case object NoType extends CachedGroundType {
     override def computeHash(bs: Binders): Int = hashSeed

compiler/src/dotty/tools/dotc/typer/TypeAssigner.scala

@@ -512,7 +512,7 @@ trait TypeAssigner {
     tree.withType(sym.termRef)
 
   def assignType(tree: untpd.Export)(using Context): Export =
-    tree.withType(ExportType)
+    tree.withType(defn.UnitType)
 
   def assignType(tree: untpd.Annotated, arg: Tree, annot: Tree)(using Context): Annotated = {
     assert(tree.isType) // annotating a term is done via a Typed node, can't use Annotate directly