Merge pull request #1813 from dotty-staging/fix-#1806

Fix #1806: Define outer accessors at the right phase

Author: DarkDimius

compiler/src/dotty/tools/dotc/core/Contexts.scala

@@ -262,6 +262,9 @@ object Contexts {
     final def withPhaseNoLater(phase: Phase) =
       if (phase.exists && ctx.phase.id > phase.id) withPhase(phase) else ctx
 
+    final def withPhaseNoEarlier(phase: Phase) =
+      if (phase.exists && ctx.phase.id < phase.id) withPhase(phase) else ctx
+
     /** If -Ydebug is on, the top of the stack trace where this context
      *  was created, otherwise `null`.
      */

compiler/src/dotty/tools/dotc/transform/ExplicitOuter.scala

@@ -147,7 +147,8 @@ object ExplicitOuter {
   private def newOuterSym(owner: ClassSymbol, cls: ClassSymbol, name: TermName, flags: FlagSet)(implicit ctx: Context) = {
     val target = cls.owner.enclosingClass.typeRef
     val info = if (flags.is(Method)) ExprType(target) else target
-    ctx.newSymbol(owner, name, Synthetic | flags, info, coord = cls.coord)
+    ctx.withPhaseNoEarlier(ctx.explicitOuterPhase.next) // outer accessors are entered at explicitOuter + 1, should not be defined before.
+       .newSymbol(owner, name, Synthetic | flags, info, coord = cls.coord)
   }
 
   /** A new param accessor for the outer field in class `cls` */

tests/neg/i1806.scala

@@ -0,0 +1,7 @@
+trait A {
+  class Inner
+ }
+trait B extends A {
+  class Inner extends super.Inner // error
+}
+

tests/repl/innerClasses.check

@@ -0,0 +1,5 @@
+scala> class A { class Inner }
+defined class A
+scala> class B extends A { class Inner2 extends super.Inner }
+defined class B
+scala> :quit