Handle refinements where the refined type is a class

Author: odersky

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

@@ -589,13 +589,14 @@ object Types {
 
       def goRefined(tp: RefinedType) = {
         val pdenot = go(tp.parent)
+        val pinfo = pdenot.info
         val rinfo = tp.refinedInfo
-        if (name.isTypeName) { // simplified case that runs more efficiently
+        if (name.isTypeName && !pinfo.isInstanceOf[ClassInfo]) { // simplified case that runs more efficiently
           val jointInfo =
             if (rinfo.isAlias) rinfo
-            else if (pdenot.info.isAlias) pdenot.info
-            else if (ctx.pendingMemberSearches.contains(name)) pdenot.info safe_& rinfo
-            else pdenot.info recoverable_& rinfo
+            else if (pinfo.isAlias) pinfo
+            else if (ctx.pendingMemberSearches.contains(name)) pinfo safe_& rinfo
+            else pinfo recoverable_& rinfo
           pdenot.asSingleDenotation.derivedSingleDenotation(pdenot.symbol, jointInfo)
         } else {
           pdenot & (

tests/neg/parser-stability-18.scala

@@ -0,0 +1,4 @@
+trait x0 {
+    class x1 (x1:x0
+    {
+type x1 <: List[x1 <:  // error // error

tests/pos/class-refinement.scala

@@ -0,0 +1,36 @@
+object Test {
+
+  class C {
+
+    class I
+
+  }
+
+  trait T
+
+  val x: C { type I <: T } = ???  // direct refinement of class member
+
+  val y: x.I = ???
+
+}
+
+class B {
+  class C {
+    type I
+  }
+  trait T
+
+  type CC <: C
+
+  val x: CC { type I <: T } = ???
+}
+
+object Test2 extends B {
+
+  class CC extends C { class I }
+
+  val y: x.I = ???        // indirect refinement of class member
+
+
+}
+