4 files changed, 47 insertions, 9 deletions

diff --git a/src/dotty/tools/dotc/TypeErasure.scala b/src/dotty/tools/dotc/TypeErasure.scala
index d2b241e71..a5dbd5731 100644
--- a/src/dotty/tools/dotc/TypeErasure.scala
+++ b/src/dotty/tools/dotc/TypeErasure.scala
@@ -1,7 +1,9 @@
-package dotty.tools.dotc
+package dotty.tools
+package dotc
 package core
 
 import Symbols._, Types._, Contexts._, Flags._, Names._, StdNames._, Decorators._, Flags.JavaDefined
+import dotc.transform.OuterAccessors._
 import util.DotClass
 
 /** Erased types are:
@@ -110,6 +112,7 @@ object TypeErasure {
 
     if ((sym eq defn.Any_asInstanceOf) || (sym eq defn.Any_isInstanceOf)) eraseParamBounds(sym.info.asInstanceOf[PolyType])
     else if (sym.isAbstractType) TypeAlias(WildcardType)
+    else if (sym.isConstructor) addOuterParam(sym.owner.asClass, erase(tp))
     else erase(tp)
   }
 
diff --git a/src/dotty/tools/dotc/transform/Erasure.scala b/src/dotty/tools/dotc/transform/Erasure.scala
index 7100e4528..6e82f050a 100644
--- a/src/dotty/tools/dotc/transform/Erasure.scala
+++ b/src/dotty/tools/dotc/transform/Erasure.scala
@@ -24,6 +24,7 @@ import scala.collection.mutable.ListBuffer
 import dotty.tools.dotc.core.Flags
 import ValueClasses._
 import TypeUtils._
+import OuterAccessors._
 import typer.Mode
 
 class Erasure extends Phase with DenotTransformer { thisTransformer =>
@@ -304,7 +305,8 @@ object Erasure {
         case fun1 =>
           fun1.tpe.widen match {
             case mt: MethodType =>
-              val args1 = (args ++ protoArgs(pt)).zipWithConserve(mt.paramTypes)(typedExpr)
+              val outers = outerArgs(fun1) map untpd.TypedSplice
+              val args1 = (outers ::: args ++ protoArgs(pt)).zipWithConserve(mt.paramTypes)(typedExpr)
               untpd.cpy.Apply(tree)(fun1, args1) withType mt.resultType
             case _ =>
               throw new MatchError(i"tree $tree has unexpected type of function ${fun1.tpe.widen}, was ${fun.typeOpt.widen}")
diff --git a/src/dotty/tools/dotc/transform/OuterAccessors.scala b/src/dotty/tools/dotc/transform/OuterAccessors.scala
index 5e6257e7f..2cad74cf3 100644
--- a/src/dotty/tools/dotc/transform/OuterAccessors.scala
+++ b/src/dotty/tools/dotc/transform/OuterAccessors.scala
@@ -80,7 +80,7 @@ class OuterAccessors extends MiniPhaseTransform with InfoTransformer { thisTrans
       if (isTrait)
         newDefs += DefDef(outerAcc, EmptyTree)
       else {
-        val outerParamAcc = cls.info.decl(nme.OUTER).symbol.asTerm
+        val outerParamAcc = outerParamAccessor(cls).asTerm
         newDefs += ValDef(outerParamAcc, EmptyTree)
         newDefs += DefDef(outerAcc, ref(outerParamAcc))
       }
@@ -132,6 +132,10 @@ object OuterAccessors {
   def hasLocalInstantiation(cls: ClassSymbol)(implicit ctx: Context): Boolean =
     cls.owner.isTerm || cls.is(LocalInstantiationSite)
 
+  /** The outer parameter accessor of cass `cls` */
+  def outerParamAccessor(cls: ClassSymbol)(implicit ctx: Context) =
+    cls.info.decl(nme.OUTER).symbol
+
   /** Class has outer accessor. Can be called only after phase OuterAccessors. */
   def hasOuter(cls: ClassSymbol)(implicit ctx: Context): Boolean =
     cls.info.decl(cls.outerAccName).exists
@@ -161,4 +165,33 @@ object OuterAccessors {
     case tpe: TypeProxy =>
       outerPrefix(tpe.underlying)
   }
+
+  /** If `cls` has an outer parameter add one to the method type `tp`. */
+  def addOuterParam(cls: ClassSymbol, tp: Type)(implicit ctx: Context): Type =
+    if (hasOuter(cls)) {
+      val mt @ MethodType(pnames, ptypes) = tp
+      mt.derivedMethodType(
+        nme.OUTER :: pnames, cls.owner.enclosingClass.typeRef :: ptypes, mt.resultType)
+    }
+    else tp
+
+  /** If function in an apply node is a constructor that needs to be passed an
+   *  outer argument, the singleton list with the argument, otherwise Nil.
+   */
+  def outerArgs(fun: Tree)(implicit ctx: Context): List[Tree] = {
+    if (fun.symbol.isConstructor) {
+      val cls = fun.symbol.owner.asClass
+      def outerArg(receiver: Tree): Tree = receiver match {
+        case New(tpt) => TypeTree(outerPrefix(tpt.tpe)).withPos(tpt.pos)
+        case This(_) => ref(outerParamAccessor(cls))
+        case TypeApply(Select(r, nme.asInstanceOf_), args) => outerArg(r) // cast was inserted, skip
+      }
+      if (hasOuter(cls))
+        methPart(fun) match {
+          case Select(receiver, _) => outerArg(receiver) :: Nil
+        }
+      else Nil
+    }
+    else Nil
+  }
 }
\ No newline at end of file
diff --git a/tests/pos/explicitOuter.scala b/tests/pos/explicitOuter.scala
index 747f07e8f..a5fb1dd70 100644
--- a/tests/pos/explicitOuter.scala
+++ b/tests/pos/explicitOuter.scala
@@ -4,8 +4,8 @@ class Outer(elem: Int, val next: Outer) {
     def foo = elem
   }
 
-  class InnerClass extends next.InnerTrait {
-    def bar = elem
+  class InnerClass(x: Int) extends next.InnerTrait {
+    def bar = elem + x
   }
 
   class EmptyInnerClass {
@@ -17,15 +17,15 @@ class Outer(elem: Int, val next: Outer) {
       def foo = elem
     }
 
-    class InnerClass extends next.InnerTrait {
-      def bar = elem
+    class InnerClass(x: Int) extends next.InnerTrait {
+      def bar = elem + x
     }
 
     class EmptyInnerClass {
       def foo = 1      // does not need outer
     }
 
-    val ic = new InnerClass
+    val ic = new InnerClass(1)
     println(ic.bar)
     println(ic.foo)
     val it = new InnerTrait {}
@@ -38,7 +38,7 @@ class Outer(elem: Int, val next: Outer) {
 object Test extends App {
 
   val o = new Outer(1, new Outer(2, null))
-  val ic = new o.InnerClass
+  val ic = new o.InnerClass(1)
   println(ic.bar)
   println(ic.foo)
   val it = new o.InnerTrait {}