Fix #2066: Don't qualify private members in SelectionProto's...

... unless they would be accessible in the given context.

Author: odersky

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

@@ -957,6 +957,10 @@ object SymDenotations {
       else
         companionNamed(name)(ctx.outersIterator.dropWhile(_.scope eq ctx.scope).next)
 
+    /** Is this symbol the same or a linked class of `sym`? */
+    final def isLinkedWith(sym: Symbol)(implicit ctx: Context): Boolean =
+      (symbol eq sym) || (linkedClass eq sym)
+
     /** If this is a class, the module class of its companion object.
      *  If this is a module class, its companion class.
      *  NoSymbol otherwise.

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

@@ -215,13 +215,13 @@ object TypeErasure {
   }
 
   /** The erased least upper bound is computed as follows
-   *  - if both argument are arrays of objects, an array of the lub of the element types
+   *  - if both argument are arrays of objects, an array of the erased lub of the element types
    *  - if both arguments are arrays of same primitives, an array of this primitive
    *  - if one argument is array of primitives and the other is array of objects, Object
    *  - if one argument is an array, Object
    *  - otherwise a common superclass or trait S of the argument classes, with the
    *    following two properties:
-   *      S is minimal: no other common superclass or trait derives from S]
+   *      S is minimal: no other common superclass or trait derives from S
    *      S is last   : in the linearization of the first argument type `tp1`
    *                    there are no minimal common superclasses or traits that
    *                    come after S.

compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala

@@ -95,7 +95,9 @@ object ProtoTypes {
 
     override def isMatchedBy(tp1: Type)(implicit ctx: Context) = {
       name == nme.WILDCARD || {
-        val mbr = tp1.member(name)
+        val mbr =
+          if (tp1.widen.classSymbol.isLinkedWith(ctx.owner.enclosingClass)) tp1.member(name)
+          else tp1.nonPrivateMember(name)
         def qualifies(m: SingleDenotation) =
           memberProto.isRef(defn.UnitClass) ||
           compat.normalizedCompatible(m.info, memberProto)

tests/pos/i2066.scala

@@ -0,0 +1,15 @@
+class Foo
+
+object Test {
+  implicit class One(x: Foo) {
+    def meth: Unit = {}
+  }
+
+  implicit class Two(x: Foo) {
+    private def meth: Unit = {}
+  }
+
+  def test(foo: Foo): Unit = {
+    foo.meth
+  }
+}