From cad41d293610ce06bfc2e6f0077080ba43264a8c Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Tue, 2 Jan 2018 19:41:31 +0100
Subject: [PATCH 1/2] Fix #3339: Disallow accesses to private package members
 from nested pkgs

Change of the accessibility rules: Disallow accesses to private package members from nested packages.
Such accesses were causing an access error at runtime before.
---
 compiler/src/dotty/tools/dotc/core/SymDenotations.scala | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
index 17390f830ecf..128f884d53aa 100644
--- a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -674,10 +674,7 @@ object SymDenotations {
     final def isAccessibleFrom(pre: Type, superAccess: Boolean = false, whyNot: StringBuffer = null)(implicit ctx: Context): Boolean = {
 
       /** Are we inside definition of `boundary`? */
-      def accessWithin(boundary: Symbol) =
-        ctx.owner.isContainedIn(boundary) &&
-          (!(this is JavaDefined) || // disregard package nesting for Java
-             ctx.owner.enclosingPackageClass == boundary.enclosingPackageClass)
+      def accessWithin(boundary: Symbol) = ctx.owner.isContainedIn(boundary)
 
       /** Are we within definition of linked class of `boundary`? */
       def accessWithinLinked(boundary: Symbol) = {
@@ -733,7 +730,9 @@ object SymDenotations {
              (  !(this is Local)
              || (owner is ImplClass) // allow private local accesses to impl class members
              || isCorrectThisType(pre)
-             )
+             ) &&
+             (!(this.is(Private) && owner.is(Package)) ||
+              owner == ctx.owner.enclosingPackageClass)
         || (this is Protected) &&
              (  superAccess
              || pre.isInstanceOf[ThisType]

From 894d77964d4563dafa357b3952eb54cb1c5a2102 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Tue, 2 Jan 2018 19:42:46 +0100
Subject: [PATCH 2/2] Improve access error messages + test case

---
 .../dotty/tools/dotc/typer/TypeAssigner.scala | 21 ++++++++++++++-----
 tests/neg/i3339.scala                         | 11 ++++++++++
 2 files changed, 27 insertions(+), 5 deletions(-)
 create mode 100644 tests/neg/i3339.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/TypeAssigner.scala b/compiler/src/dotty/tools/dotc/typer/TypeAssigner.scala
index 59210fde2ea7..483140e3069a 100644
--- a/compiler/src/dotty/tools/dotc/typer/TypeAssigner.scala
+++ b/compiler/src/dotty/tools/dotc/typer/TypeAssigner.scala
@@ -195,19 +195,30 @@ trait TypeAssigner {
             TryDynamicCallType
           } else {
             val alts = tpe.denot.alternatives.map(_.symbol).filter(_.exists)
+            var packageAccess = false
             val what = alts match {
               case Nil =>
-                name.toString
+                i"$name cannot be accessed as a member of $pre"
               case sym :: Nil =>
-                if (sym.owner == pre.typeSymbol) sym.show else sym.showLocated
+                if (sym.owner.is(Package)) {
+                  packageAccess = true
+                  i"${sym.showLocated} cannot be accessed"
+                }
+                else {
+                  val symStr = if (sym.owner == pre.typeSymbol) sym.show else sym.showLocated
+                  i"$symStr cannot be accessed as a member of $pre"
+                }
               case _ =>
-                em"none of the overloaded alternatives named $name"
+                em"none of the overloaded alternatives named $name can be accessed as members of $pre"
             }
-            val where = if (ctx.owner.exists) s" from ${ctx.owner.enclosingClass}" else ""
+            val where =
+              if (!ctx.owner.exists) ""
+              else if (packageAccess) i" from nested ${ctx.owner.enclosingPackageClass}"
+              else i" from ${ctx.owner.enclosingClass}"
             val whyNot = new StringBuffer
             alts foreach (_.isAccessibleFrom(pre, superAccess, whyNot))
             if (tpe.isError) tpe
-            else errorType(ex"$what cannot be accessed as a member of $pre$where.$whyNot", pos)
+            else errorType(ex"$what$where.$whyNot", pos)
           }
         }
         else ctx.makePackageObjPrefixExplicit(tpe withDenot d)
diff --git a/tests/neg/i3339.scala b/tests/neg/i3339.scala
new file mode 100644
index 000000000000..7494df2b6f99
--- /dev/null
+++ b/tests/neg/i3339.scala
@@ -0,0 +1,11 @@
+package outer {
+  private class A
+
+  package inner {
+    object Test {
+      def main(args: Array[String]): Unit = {
+        println(new A)  // error: cannot access
+      }
+    }
+  }
+}