1 files changed, 13 insertions, 0 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 6a9d3b9ab4..e5c82085fb 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -69,6 +69,8 @@ abstract class RefChecks extends InfoTransform {
      *    1.8.2  M is of type []S, O is of type ()T and S <: T, or
      *    1.8.3  M is of type ()S, O is of type []T and S <: T, or
      *  2. Check that only abstract classes have deferred members
+     *  3. Check that every member with an `override' modifier
+     *     overrides some other member.
      */
     private def checkAllOverrides(clazz: Symbol): unit = {
 
@@ -239,6 +241,17 @@ abstract class RefChecks extends InfoTransform {
 	       else ""))
 	  }
       }
+
+      // 3. Check that every defined member with an `override' modifier overrides some other member.
+      for (val member <- clazz.info.decls.toList)
+	if ((member hasFlag (OVERRIDE | ABSOVERRIDE)) &&
+	    (clazz.info.baseClasses.tail forall {
+               bc => member.matchingSymbol(bc, clazz.thisType) == NoSymbol
+            })) {
+          // for (val bc <- clazz.info.baseClasses.tail) System.out.println("" + bc + " has " + bc.info.decl(member.name) + ":" + bc.info.decl(member.name).tpe);//DEBUG
+	  unit.error(member.pos, member.toString() + " overrides nothing");
+	  member resetFlag OVERRIDE
+	}
     }
 
   // Basetype Checking --------------------------------------------------------