Fix: handle accesses to private aliases from inlined code

Dealias them and try again.

Author: odersky

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

@@ -26,6 +26,7 @@ import ErrorReporting.errorTree
 import collection.mutable
 import transform.TypeUtils._
 import reporting.trace
+import util.Positions.Position
 
 object Inliner {
   import tpd._
@@ -538,6 +539,18 @@ class Inliner(call: tpd.Tree, rhs: tpd.Tree)(implicit ctx: Context) {
 
     var retainedInlineables = Set[Symbol]()
 
+    override def ensureAccessible(tpe: Type, superAccess: Boolean, pos: Position)(implicit ctx: Context): Type = {
+      tpe match {
+        case tpe @ TypeRef(pre, _) if !tpe.symbol.isAccessibleFrom(pre, superAccess) =>
+          tpe.info match {
+            case TypeAlias(alias) => return ensureAccessible(alias, superAccess, pos)
+            case _ =>
+          }
+        case _ =>
+      }
+      super.ensureAccessible(tpe, superAccess, pos)
+    }
+
     override def typedIdent(tree: untpd.Ident, pt: Type)(implicit ctx: Context) =
       tree.asInstanceOf[tpd.Tree] match {
         case InlineableArg(rhs) => inlining.println(i"inline arg $tree -> $rhs"); rhs

tests/pos/inlineAccesses.scala

@@ -0,0 +1,22 @@
+trait T {
+  object O
+}
+
+class C {
+  private type T = C
+  private var x = 0
+
+  inline def f = {
+    x += 1
+    x = x + 1
+    x
+  }
+  inline def dup = new T
+}
+
+object Test {
+
+  val c = new C
+  c.f
+  c.dup
+}