Clean up code relating to interfaces.

Previous implementation was confused about the meaning of interface (with default methods
or without?).

Now instead of Interface/JavaInterface we have

    PureInterface   - all members are abstract methods
    NoInits         - all members are methods

1 files changed, 9 insertions, 6 deletions

diff --git a/src/dotty/tools/dotc/ast/TreeInfo.scala b/src/dotty/tools/dotc/ast/TreeInfo.scala
index 51e1ff16f..8163c8bcc 100644
--- a/src/dotty/tools/dotc/ast/TreeInfo.scala
+++ b/src/dotty/tools/dotc/ast/TreeInfo.scala
@@ -26,15 +26,18 @@ trait TreeInfo[T >: Untyped <: Type] { self: Trees.Instance[T] =>
 
   /** Is tree legal as a member definition of an interface?
    */
-  def isInterfaceMember(tree: Tree): Boolean = unsplice(tree) match {
-    case EmptyTree => true
-    case Import(_, _) => true
-    case TypeDef(_, _, _) => true
-    case DefDef(mods, _, _, _, _, __) => mods.flags is Deferred
-    case ValDef(mods, _, _, _) => mods is Deferred
+  def isPureInterfaceMember(tree: Tree): Boolean = unsplice(tree) match {
+    case EmptyTree | Import(_, _) | TypeDef(_, _, _) => true
+    case DefDef(_, _, _, _, _, rhs) => rhs.isEmpty
+    case ValDef(mods, _, _, rhs) => rhs.isEmpty
     case _ => false
   }
 
+  /** Is tree legal as a member definition of a no-init trait?
+   */
+  def isNoInitMember(tree: Tree): Boolean =
+    isPureInterfaceMember(tree) || unsplice(tree).isInstanceOf[DefDef]
+
   def isOpAssign(tree: Tree) = unsplice(tree) match {
     case Apply(fn, _ :: Nil) =>
       unsplice(fn) match {