SD-128 fix override checks for default methods

The check for inheriting two conflicting members was wrong for default
methods, leading to a missing error message.

We were also not issuing "needs `override' modifier" when overriding a
default method.

Removes two methods:

  - `isDeferredOrJavaDefault` had a single use that is removed in this commit.

  - `isDeferredNotJavaDefault` is redundant with `isDeferred`, because
no default method has the `DEFERRED` flag:
    - For symbols originating in the classfile parser this was the case
      from day one: default methods don't receive the `DEFERRED` flag.
      Only abstract interface methods do, as they have the `JAVA_ACC_ABSTRACT`
      flag in bytecode, which the classfile parser translates to `DEFERRED`.

    - For symbols created by the Java source parser, we don't add the
      `DEFERRED` to default methods anymore since 373db1e.

Fixes scala/scala-dev#128

2 files changed, 1 insertions, 4 deletions

diff --git a/src/reflect/scala/reflect/internal/Definitions.scala b/src/reflect/scala/reflect/internal/Definitions.scala
index eca1bbea5a..5025c1fa6d 100644
--- a/src/reflect/scala/reflect/internal/Definitions.scala
+++ b/src/reflect/scala/reflect/internal/Definitions.scala
@@ -855,7 +855,7 @@ trait Definitions extends api.StandardDefinitions {
         // must filter out "universal" members (getClass is deferred for some reason)
         val deferredMembers = (
           tp.membersBasedOnFlags(excludedFlags = BridgeAndPrivateFlags, requiredFlags = METHOD).toList.filter(
-            mem => mem.isDeferredNotJavaDefault && !isUniversalMember(mem)
+            mem => mem.isDeferred && !isUniversalMember(mem)
           ) // TODO: test
         )
 
diff --git a/src/reflect/scala/reflect/internal/HasFlags.scala b/src/reflect/scala/reflect/internal/HasFlags.scala
index e793586e18..dfada48c5e 100644
--- a/src/reflect/scala/reflect/internal/HasFlags.scala
+++ b/src/reflect/scala/reflect/internal/HasFlags.scala
@@ -122,9 +122,6 @@ trait HasFlags {
   def isTrait               = hasFlag(TRAIT) && !hasFlag(PARAM)
   def isTraitOrInterface    = isTrait || isInterface
 
-  def isDeferredOrJavaDefault  = hasFlag(DEFERRED | JAVA_DEFAULTMETHOD)
-  def isDeferredNotJavaDefault = isDeferred && !hasFlag(JAVA_DEFAULTMETHOD)
-
   def flagBitsToString(bits: Long): String = {
     // Fast path for common case
     if (bits == 0L) "" else {