Add checking for leaking private definitions

First version. Fixes #997.

5 files changed, 98 insertions, 5 deletions

diff --git a/src/dotty/tools/dotc/core/Flags.scala b/src/dotty/tools/dotc/core/Flags.scala
index 02b341649..d1f562f72 100644
--- a/src/dotty/tools/dotc/core/Flags.scala
+++ b/src/dotty/tools/dotc/core/Flags.scala
@@ -543,6 +543,9 @@ object Flags {
   /** A lazy or deferred value */
   final val LazyOrDeferred = Lazy | Deferred
 
+  /** A synthetic or private definition */
+  final val SyntheticOrPrivate = Synthetic | Private
+
   /** A type parameter or type parameter accessor */
   final val TypeParamOrAccessor = TypeParam | TypeParamAccessor
 
diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index 8595da640..16287c827 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -1014,6 +1014,12 @@ object Types {
       case _ => List()
     }
 
+    /** The full parent types, including all type arguments */
+    def parentsWithArgs(implicit ctx: Context): List[Type] = this match {
+      case tp: TypeProxy => tp.underlying.parents
+      case _ => List()
+    }
+
     /** The first parent of this type, AnyRef if list of parents is empty */
     def firstParent(implicit ctx: Context): TypeRef = parents match {
       case p :: _ => p
@@ -2780,6 +2786,9 @@ object Types {
       parentsCache
     }
 
+    override def parentsWithArgs(implicit ctx: Context): List[Type] =
+      parents.map(p => typeRef.baseTypeWithArgs(p.symbol))
+
     /** The parent types with all type arguments */
     def instantiatedParents(implicit ctx: Context): List[Type] =
       parents mapConserve { pref =>
diff --git a/src/dotty/tools/dotc/transform/PostTyper.scala b/src/dotty/tools/dotc/transform/PostTyper.scala
index 14edaa7b5..b4b01d1f3 100644
--- a/src/dotty/tools/dotc/transform/PostTyper.scala
+++ b/src/dotty/tools/dotc/transform/PostTyper.scala
@@ -127,8 +127,42 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer  { thisTran
     private def transformAnnot(annot: Annotation)(implicit ctx: Context): Annotation =
       annot.derivedAnnotation(transformAnnot(annot.tree))
 
-    private def transformAnnots(tree: MemberDef)(implicit ctx: Context): Unit =
-      tree.symbol.transformAnnotations(transformAnnot)
+    private def transformMemberDef(tree: MemberDef)(implicit ctx: Context): Unit = {
+      val sym = tree.symbol
+      sym.transformAnnotations(transformAnnot)
+      type Errors = List[(String, Position)]
+      val notPrivate = new TypeAccumulator[Errors] {
+        def boundary(sym: Symbol): Symbol =
+          if (sym.is(Private)) sym.owner
+          else if (sym.privateWithin.exists) sym.privateWithin
+          else if (sym.is(Package)) sym
+          else boundary(sym.owner)
+        def apply(errors: Errors, tp: Type): Errors = tp match {
+          case tp: NamedType =>
+            val errors1 =
+              if (tp.symbol.is(Private) &&
+                  !boundary(sym).isContainedIn(boundary(tp.symbol))) {
+                //println(i"sym = $sym, ref = ${tp.symbol}, symb = ${boundary(sym)}, refb = ${boundary(tp.symbol)}")
+                (d"non-private $sym refers to private ${tp.symbol}\n in its type signature ${sym.info}", tree.pos) :: errors
+              }
+              else foldOver(errors, tp)
+            if ((errors1 ne errors) && tp.info.isAlias) {
+              val errors2 = apply(errors, tp.info.bounds.hi)
+              if (errors2 eq errors) errors2
+              else errors1
+            }
+            else errors1
+          case tp: ClassInfo =>
+            (apply(errors, tp.prefix) /: tp.typeRef.parentsWithArgs)(apply)
+          case _ =>
+            foldOver(errors, tp)
+        }
+      }
+      if (!sym.is(SyntheticOrPrivate) && sym.owner.isClass) {
+        val errors = notPrivate(Nil, sym.info)
+        errors.foreach { case (msg, pos) => ctx.errorOrMigrationWarning(msg, pos) }
+      }
+    }
 
     private def transformSelect(tree: Select, targs: List[Tree])(implicit ctx: Context): Tree = {
       val qual = tree.qualifier
@@ -172,10 +206,10 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer  { thisTran
           }
           finally parentNews = saved
         case tree: DefDef =>
-          transformAnnots(tree)
+          transformMemberDef(tree)
           superAcc.wrapDefDef(tree)(super.transform(tree).asInstanceOf[DefDef])
         case tree: TypeDef =>
-          transformAnnots(tree)
+          transformMemberDef(tree)
           val sym = tree.symbol
           val tree1 =
             if (sym.isClass) tree
@@ -185,7 +219,7 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer  { thisTran
             }
           super.transform(tree1)
         case tree: MemberDef =>
-          transformAnnots(tree)
+          transformMemberDef(tree)
           super.transform(tree)
         case tree: New if !inJavaAnnot && !parentNews.contains(tree) =>
           Checking.checkInstantiable(tree.tpe, tree.pos)
diff --git a/test/dotc/tests.scala b/test/dotc/tests.scala
index 421846ca2..573436733 100644
--- a/test/dotc/tests.scala
+++ b/test/dotc/tests.scala
@@ -165,6 +165,8 @@ class tests extends CompilerTest {
   @Test def neg_i803 = compileFile(negDir, "i803", xerrors = 2)
   @Test def neg_i866 = compileFile(negDir, "i866", xerrors = 2)
   @Test def neg_i974 = compileFile(negDir, "i974", xerrors = 2)
+  @Test def neg_i997 = compileFile(negDir, "i997a", xerrors = 15)
+  @Test def neg_i997a = compileFile(negDir, "i997a", xerrors = 2)
   @Test def neg_i1050 = compileFile(negDir, "i1050", List("-strict"), xerrors = 11)
   @Test def neg_i1050a = compileFile(negDir, "i1050a", xerrors = 2)
   @Test def neg_i1050c = compileFile(negDir, "i1050c", xerrors = 8)
diff --git a/tests/neg/i997.scala b/tests/neg/i997.scala
new file mode 100644
index 000000000..bfcf5637e
--- /dev/null
+++ b/tests/neg/i997.scala
@@ -0,0 +1,45 @@
+class C {
+
+  private type T = E
+  private val p: C = new C
+
+  def f1(x: T): Unit = () // error
+  def f2(x: p.D): Unit = () // error
+
+  val v1: T = ??? // error
+  val v2: p.D = ??? // error
+
+  type U1[X <: T] // error
+  type U2 = T // error
+
+  private class E {
+    def f1ok(x: T): Unit = () // ok
+    def f2ok(x: p.D): Unit = () // ok
+
+    val v1ok: T = ??? // ok
+    val v2ok: p.D = ??? // ok
+
+    type U1ok[X <: T] //ok
+    type U2ok = T //ok
+  }
+
+  class D extends E { // error
+    def f1(x: T): Unit = () // error
+    def f2(x: p.D): Unit = () // error
+
+    val v1: T = ??? // error
+    val v2: p.D = ??? // error
+
+    type U1[X <: T] // error
+    type U2 = T // error
+  }
+
+  class F(x: T) // error
+
+  class G private (x: T) // ok
+
+  private trait U
+
+  class H extends U // error
+
+}