Fix problem when handling structural types without a nominal parent type.

We need to use Object as parent then, but this was forgotten.

2 files changed, 4 insertions, 2 deletions

diff --git a/src/dotty/tools/dotc/ast/Desugar.scala b/src/dotty/tools/dotc/ast/Desugar.scala
index 473800cde..027c3238d 100644
--- a/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/src/dotty/tools/dotc/ast/Desugar.scala
@@ -715,10 +715,12 @@ object desugar {
    *  ==>
    *      trait <refinement> extends parent { refinements }
    *
+   *  If the parent is missing, Object is assumed.
    *  The result is used for validity checking, is thrown away afterwards.
    */
   def refinedTypeToClass(tree: RefinedTypeTree)(implicit ctx: Context): TypeDef = {
-    val impl = Template(emptyConstructor, tree.tpt :: Nil, EmptyValDef, tree.refinements)
+    val parent = if (tree.tpt.isEmpty) TypeTree(defn.ObjectType) else tree.tpt
+    val impl = Template(emptyConstructor, parent :: Nil, EmptyValDef, tree.refinements)
     TypeDef(Modifiers(Trait), tpnme.REFINE_CLASS, impl)
   }
 
diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index ebb648ea5..400a1407a 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/src/dotty/tools/dotc/typer/Typer.scala
@@ -798,7 +798,7 @@ class Typer extends Namer with Applications with Implicits {
   }
 
   def typedRefinedTypeTree(tree: untpd.RefinedTypeTree)(implicit ctx: Context): RefinedTypeTree = track("typedRefinedTypeTree") {
-    val tpt1 = typedAheadType(tree.tpt)
+    val tpt1 = if (tree.tpt.isEmpty) TypeTree(defn.ObjectType) else typedAheadType(tree.tpt)
     val refineClsDef = desugar.refinedTypeToClass(tree)
     val refineCls = createSymbol(refineClsDef).asClass
     val TypeDef(_, _, Template(_, _, _, refinements1)) = typed(refineClsDef)