Fixes #2808 without redefining what override me...

Fixes #2808 without redefining what override means. Review by extempore.

2 files changed, 10 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/symtab/Symbols.scala b/src/compiler/scala/tools/nsc/symtab/Symbols.scala
index c558610535..d17077b129 100644
--- a/src/compiler/scala/tools/nsc/symtab/Symbols.scala
+++ b/src/compiler/scala/tools/nsc/symtab/Symbols.scala
@@ -1401,8 +1401,17 @@ trait Symbols extends reflect.generic.Symbols { self: SymbolTable =>
     final def overridingSymbol(ofclazz: Symbol): Symbol =
       if (isClassConstructor) NoSymbol else matchingSymbol(ofclazz, ofclazz.thisType)
 
+    /** Returns all symbols overriden by this symbol
+     */
     final def allOverriddenSymbols: List[Symbol] =
       if (!owner.isClass) Nil
+      else owner.ancestors map overriddenSymbol filter (_ != NoSymbol)
+
+    /** Returns all symbols overridden by this symbol, plus all matching symbols
+     *  defined in parents of the selftype
+     */
+    final def extendedOverriddenSymbols: List[Symbol] =
+      if (!owner.isClass) Nil
       else owner.thisSym.ancestors map overriddenSymbol filter (_ != NoSymbol)
 
     /** The symbol accessed by a super in the definition of this symbol when
diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 63542e6dd5..18413de51f 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -352,7 +352,7 @@ abstract class RefChecks extends InfoTransform {
           } else if ((member hasFlag (OVERRIDE | ABSOVERRIDE)) &&
                      !(member.owner.thisType.baseClasses exists (_ isSubClass other.owner)) &&
                      !member.isDeferred && !other.isDeferred &&
-                     intersectionIsEmpty(member.allOverriddenSymbols, other.allOverriddenSymbols)) {
+                     intersectionIsEmpty(member.extendedOverriddenSymbols, other.extendedOverriddenSymbols)) {
             overrideError("cannot override a concrete member without a third member that's overridden by both "+
                           "(this rule is designed to prevent ``accidental overrides'')")
           } else if (other.isStable && !member.isStable) { // (1.4)