Add initializers for lambdalift proxy fields

If an inner class has proxy fields, we missed so far the assignment sfrom
the proxy parameters in the primary constructor of the class to the proxy
fields.

Test case tries several variations of this.

Author: odersky

src/dotty/tools/dotc/ast/tpd.scala

@@ -76,8 +76,13 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   def Block(stats: List[Tree], expr: Tree)(implicit ctx: Context): Block =
     ta.assignType(untpd.Block(stats, expr), stats, expr)
 
-  def maybeBlock(stats: List[Tree], expr: Tree)(implicit ctx: Context): Tree =
-    if (stats.isEmpty) expr else Block(stats, expr)
+  /** Join `stats` in front of `expr` creating a new block if necessary */
+  def seq(stats: List[Tree], expr: Tree)(implicit ctx: Context): Tree =
+    if (stats.isEmpty) expr
+    else expr match {
+      case Block(estats, eexpr) => cpy.Block(expr)(stats ::: estats, eexpr)
+      case _ => Block(stats, expr)
+    }
 
   def If(cond: Tree, thenp: Tree, elsep: Tree)(implicit ctx: Context): If =
     ta.assignType(untpd.If(cond, thenp, elsep), thenp, elsep)

src/dotty/tools/dotc/transform/LambdaLift.scala

@@ -384,14 +384,23 @@ class LambdaLift extends MiniPhase with IdentityDenotTransformer { thisTransform
     private def addFreeParams(tree: Tree, proxies: List[Symbol])(implicit ctx: Context, info: TransformerInfo): Tree = proxies match {
       case Nil => tree
       case proxies =>
+        val sym = tree.symbol
         val ownProxies =
-          if (!tree.symbol.isConstructor) proxies
-          else proxies.map(_.copy(owner = tree.symbol, flags = Synthetic | Param))
+          if (!sym.isConstructor) proxies
+          else proxies.map(_.copy(owner = sym, flags = Synthetic | Param))
         val freeParamDefs = ownProxies.map(proxy =>
           transformFollowingDeep(ValDef(proxy.asTerm).withPos(tree.pos)).asInstanceOf[ValDef])
+        def proxyInit(field: Symbol, param: Symbol) =
+          transformFollowingDeep(ref(field).becomes(ref(param)))
+        def copyParams(rhs: Tree) = {
+          ctx.log(i"copy params ${proxies.map(_.showLocated)}%, %, own = ${ownProxies.map(_.showLocated)}%, %")
+          seq((proxies, ownProxies).zipped.map(proxyInit), rhs)
+        }
         tree match {
           case tree: DefDef =>
-            cpy.DefDef(tree)(vparamss = tree.vparamss.map(freeParamDefs ++ _))
+            cpy.DefDef(tree)(
+                vparamss = tree.vparamss.map(freeParamDefs ++ _),
+                rhs = if (sym.isPrimaryConstructor) copyParams(tree.rhs) else tree.rhs)
           case tree: Template =>
             cpy.Template(tree)(body = freeParamDefs ++ tree.body)
         }

tests/run/i659.scala

@@ -1,12 +1,26 @@
 class Foo(val a: Int) {
-  //def foo = { {case x => x + a}: PartialFunction[Int, Int]}
+  def foo = { {case x => x + a}: PartialFunction[Int, Int]}
   class Bar { def result(x: Int) = x + a }
   def bar = new Bar
 }
 
+class VFoo(val a: Int) extends AnyVal {
+  def foo = { {case x => x + a}: PartialFunction[Int, Int]}
+}
+
 object Test extends dotty.runtime.LegacyApp {
-  //val x = new Foo(1).foo.apply(2)
-  val y = new Foo(1).bar.result(2)
-  assert(y == 3, y)
-  //assert(x == 3, x)
+
+  def Foo(a: Int) = {
+    class Bar { def result(x: Int) = x + a }
+    new Bar().result(2)
+  }
+
+  val x1 = new Foo(1).bar.result(2)
+  assert(x1 == 3, s"x1 = $x1")
+  val x2 = Foo(1)
+  assert(x2 == 3, s"x2 = $x2")
+  val x3 = new Foo(1).foo.apply(2)
+  assert(x3 == 3, s"x3 = $x3")
+  val x4 = new VFoo(1).foo.apply(2)
+  assert(x4 == 3, s"x4 = $x4")
 }