Fix #756 super accessors

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

@@ -167,6 +167,11 @@ object NameOps {
 
     def expandedName(prefix: Name): N = expandedName(prefix, nme.EXPAND_SEPARATOR)
 
+    /** Revert the expanded name. Note: This currently gives incorrect results
+     *  if the normal name contains `nme.EXPAND_SEPARATOR`, i.e. two consecutive '$'
+     *  signs. This can happen for instance if a super accessor is paired with
+     *  an encoded name, e.g. super$$plus$eq. See #765.
+     */
     def unexpandedName: N = {
       val idx = name.lastIndexOfSlice(nme.EXPAND_SEPARATOR)
       if (idx < 0) name else (name drop (idx + nme.EXPAND_SEPARATOR.length)).asInstanceOf[N]

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

@@ -59,7 +59,13 @@ class ResolveSuper extends MiniPhaseTransform with IdentityDenotTransformer { th
   private def rebindSuper(base: Symbol, acc: Symbol)(implicit ctx: Context): Symbol = {
     var bcs = base.info.baseClasses.dropWhile(acc.owner != _).tail
     var sym: Symbol = NoSymbol
-    val SuperAccessorName(memberName) = ctx.atPhase(ctx.picklerPhase){ implicit ctx => acc.name }: Name // dotty deviation: ": Name" needed otherwise pattern type is neither a subtype nor a supertype of selector type
+    val unexpandedAccName =
+      if (acc.is(ExpandedName))  // Cannot use unexpandedName because of #765. t2183.scala would fail if we did.
+        acc.name
+          .drop(acc.name.indexOfSlice(nme.EXPAND_SEPARATOR ++ nme.SUPER_PREFIX))
+          .drop(nme.EXPAND_SEPARATOR.length)
+      else acc.name
+    val SuperAccessorName(memberName) = unexpandedAccName: Name // dotty deviation: ": Name" needed otherwise pattern type is neither a subtype nor a supertype of selector type
     ctx.debuglog(i"starting rebindsuper from $base of ${acc.showLocated}: ${acc.info} in $bcs, name = $memberName")
     while (bcs.nonEmpty && sym == NoSymbol) {
       val other = bcs.head.info.nonPrivateDecl(memberName)

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

@@ -71,11 +71,12 @@ class SuperAccessors(thisTransformer: DenotTransformer) {
       val Select(qual, name) = sel
       val sym = sel.symbol
       val clazz = qual.symbol.asClass
-      val supername = name.superName
+      var supername = name.superName
+      if (clazz is Trait) supername = supername.expandedName(clazz)
 
       val superAcc = clazz.info.decl(supername).suchThat(_.signature == sym.signature).symbol orElse {
         ctx.debuglog(s"add super acc ${sym.showLocated} to $clazz")
-        val deferredOrPrivate = if (clazz is Trait) Deferred else Private
+        val deferredOrPrivate = if (clazz is Trait) Deferred | ExpandedName else Private
         val acc = ctx.newSymbol(
             clazz, supername, SuperAccessor | Artifact | Method | deferredOrPrivate,
             sel.tpe.widenSingleton.ensureMethodic, coord = sym.coord).enteredAfter(thisTransformer)
@@ -106,10 +107,11 @@ class SuperAccessors(thisTransformer: DenotTransformer) {
         val member = sym.overridingSymbol(clazz)
         if (mix != tpnme.EMPTY ||
             !member.exists ||
-            !(member is AbsOverride) && member.isIncompleteIn(clazz))
+            !((member is AbsOverride) && member.isIncompleteIn(clazz)))
           ctx.error(
               i"${sym.showLocated} is accessed from super. It may not be abstract unless it is overridden by a member declared `abstract' and `override'",
               sel.pos)
+        else println(i"ok super $sel ${sym.showLocated} $member $clazz ${member.isIncompleteIn(clazz)}")
       }
       else if (mix == tpnme.EMPTY && !(sym.owner is Trait))
         // SI-4989 Check if an intermediate class between `clazz` and `sym.owner` redeclares the method as abstract.

test/dotc/tests.scala

@@ -96,6 +96,7 @@ class tests extends CompilerTest {
 
   @Test def new_all = compileFiles(newDir, twice)
 
+  @Test def neg_abstractOverride() = compileFile(negDir, "abstract-override", xerrors = 2)
   @Test def neg_blockescapes() = compileFile(negDir, "blockescapesNeg", xerrors = 1)
   @Test def neg_typedapply() = compileFile(negDir, "typedapply", xerrors = 4)
   @Test def neg_typedidents() = compileFile(negDir, "typedIdents", xerrors = 2)

tests/neg/abstract-override.scala

@@ -0,0 +1,8 @@
+trait T { def foo: Int }
+trait T1 extends T { override def foo = super.foo }
+trait T2 extends T { override def foo = super.foo }
+object Test extends T2 with T1 {
+  def main(args: Array[String]) = {
+    assert(foo == 3)
+  }
+}

tests/run/i756.scala

@@ -0,0 +1,8 @@
+trait T { def foo: Int = 3 }
+trait T1 extends T { override def foo = super.foo }
+trait T2 extends T { override def foo = super.foo }
+object Test extends T2 with T1 {
+  def main(args: Array[String]) = {
+    assert(foo == 3)
+  }
+}