Added utility method: underlyingSymbol

Author: odersky

src/dotty/tools/dotc/core/SymDenotations.scala

@@ -598,6 +598,13 @@ object SymDenotations {
       field orElse getter
     }
 
+    /** The field accessed by a getter or setter, or
+     *  if it does not exists, the getter of a setter, or
+     *  if that does not exist the symbol itself.
+     */
+    def underlyingSymbol(implicit ctx: Context): Symbol =
+      if (is(Accessor)) accessedFieldOrGetter orElse symbol else symbol
+
     /** The chain of owners of this denotation, starting with the denoting symbol itself */
     final def ownersIterator(implicit ctx: Context) = new Iterator[Symbol] {
       private[this] var current = symbol

src/dotty/tools/dotc/transform/SuperAccessors.scala

@@ -356,7 +356,7 @@ class SuperAccessors extends MacroTransform with IdentityDenotTransformer { this
 
               case Super(_, mix) =>
                 if ((sym.isTerm) && !(sym is Method) || (sym is Accessor)) {
-                  ctx.error(s"super may be not be used on ${sym.accessedFieldOrGetter orElse sym}", tree.pos)
+                  ctx.error(s"super may be not be used on ${sym.underlyingSymbol}", tree.pos)
                 } else if (isDisallowed(sym)) {
                   ctx.error(s"super not allowed here: use this.${name.decode} instead", tree.pos)
                 }

src/dotty/tools/dotc/typer/ErrorReporting.scala

@@ -6,7 +6,7 @@ import ast._
 import core._
 import Trees._
 import Types._, ProtoTypes._, Contexts._, Decorators._, Denotations._, Symbols._
-import Applications._, Implicits._
+import Applications._, Implicits._, Flags._
 import util.Positions._
 import printing.Showable
 import printing.Disambiguation.disambiguated
@@ -48,6 +48,13 @@ object ErrorReporting {
 
   class Errors(implicit ctx: Context) {
 
+    /** An explanatory note to be added to error messages
+     *  when there's a problem with abstract var defs */
+    def abstractVarMessage(sym: Symbol): String =
+      if (sym.underlyingSymbol.is(Mutable))
+        "\n(Note that variables need to be initialized to be defined)"
+      else ""
+
     def expectedTypeStr(tp: Type): String = tp match {
       case tp: FunProto =>
         val result = tp.resultType match {