Made lub/glb fail early when trying to mix a class info with another type type.

The previous alternative of creating a TypeBounds with the TypeRef back to the class leads to infinite loops when chasing type proxies. Example was infinite loop in baseClasses in showClass test.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index 36a4986b4..0370d0a1f 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -2288,6 +2288,15 @@ object Types {
   class CyclicReference(val denot: SymDenotation)
     extends FatalTypeError(s"cyclic reference involving $denot")
 
+  class ClassMergeError(cinfo: ClassInfo, tp2: Type)(implicit ctx: Context)
+    extends FatalTypeError(s"cannot merge ${showTypeType(cinfo)} with ${showTypeType(tp2)} as members of ${cinfo.prefix.show}")
+
+  private def showTypeType(tp: Type)(implicit ctx: Context) = tp match {
+    case ClassInfo(_, cls, _, _, _) => cls.showLocated
+    case bounds: TypeBounds => "type bounds" + bounds.show
+    case _ => tp.show
+  }
+
   // ----- Debug ---------------------------------------------------------
 
   var debugTrace = false