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

1 files changed, 2 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index 72133f31fa..8449260fe6 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -419,7 +419,7 @@ abstract class RefChecks extends Transform {
             overrideError("cannot be used here - classes can only override abstract types")
           } else if (other.isEffectivelyFinal) { // (1.2)
             overrideError("cannot override final member")
-          } else if (!other.isDeferredOrJavaDefault && !other.hasFlag(JAVA_DEFAULTMETHOD) && !member.isAnyOverride && !member.isSynthetic) { // (*)
+          } else if (!other.isDeferred && !member.isAnyOverride && !member.isSynthetic) { // (*)
             // (*) Synthetic exclusion for (at least) default getters, fixes SI-5178. We cannot assign the OVERRIDE flag to
             // the default getter: one default getter might sometimes override, sometimes not. Example in comment on ticket.
               if (isNeitherInClass && !(other.owner isSubClass member.owner))
@@ -606,7 +606,7 @@ abstract class RefChecks extends Transform {
         def checkNoAbstractMembers(): Unit = {
           // Avoid spurious duplicates: first gather any missing members.
           def memberList = clazz.info.nonPrivateMembersAdmitting(VBRIDGE)
-          val (missing, rest) = memberList partition (m => m.isDeferredNotJavaDefault && !ignoreDeferred(m))
+          val (missing, rest) = memberList partition (m => m.isDeferred && !ignoreDeferred(m))
           // Group missing members by the name of the underlying symbol,
           // to consolidate getters and setters.
           val grouped = missing groupBy (sym => analyzer.underlyingSymbol(sym).name)