Get rid of TypeBounds.onAlias

This was the last bit that tested for the fragile `lo eq hi` condition.

Author: odersky

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

@@ -2483,9 +2483,6 @@ object Types {
   object TypeBounds {
     def apply(lo: Type, hi: Type)(implicit ctx: Context): TypeBounds =
       unique(new RealTypeBounds(lo, hi))
-    def orAlias(lo: Type, hi: Type)(implicit ctx: Context): TypeBounds =
-      if (lo eq hi) TypeAlias(lo, 0)
-      else unique(new RealTypeBounds(lo, hi))
     def empty(implicit ctx: Context) = apply(defn.NothingType, defn.AnyType)
     def upper(hi: Type)(implicit ctx: Context) = apply(defn.NothingType, hi)
     def lower(lo: Type)(implicit ctx: Context) = apply(lo, defn.AnyType)

src/dotty/tools/dotc/core/pickling/UnPickler.scala

@@ -656,7 +656,7 @@ class UnPickler(bytes: Array[Byte], classRoot: ClassDenotation, moduleClassRoot:
         if (sym == defn.ByNameParamClass2x) ExprType(args.head)
         else tycon.appliedTo(args)
       case TYPEBOUNDStpe =>
-        TypeBounds.orAlias(readTypeRef(), readTypeRef())
+        TypeBounds(readTypeRef(), readTypeRef())
       case REFINEDtpe =>
         val clazz = readSymbolRef()
         val decls = symScope(clazz)

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

@@ -355,7 +355,7 @@ trait TypeAssigner {
     tree.withType(ExprType(result.tpe))
 
   def assignType(tree: untpd.TypeBoundsTree, lo: Tree, hi: Tree)(implicit ctx: Context) =
-    tree.withType(TypeBounds.orAlias(lo.tpe, hi.tpe))
+    tree.withType(if (lo eq hi) TypeAlias(lo.tpe) else TypeBounds(lo.tpe, hi.tpe))
 
   def assignType(tree: untpd.Bind, sym: TermSymbol)(implicit ctx: Context) =
     tree.withType(TermRef(NoPrefix, sym))