New miniphase: Flatten

Author: odersky

src/dotty/tools/dotc/Compiler.scala

@@ -55,7 +55,8 @@ class Compiler {
       List(new Erasure),
       List(new CapturedVars,
            new Constructors),
-      List(new LambdaLift)
+      List(new LambdaLift,
+           new Flatten)
     )
 
   var runId = 1

src/dotty/tools/dotc/Flatten.scala

@@ -0,0 +1,49 @@
+package dotty.tools.dotc
+package transform
+
+import core._
+import DenotTransformers.SymTransformer
+import Phases.Phase
+import Contexts.Context
+import Flags._
+import SymUtils._
+import SymDenotations.SymDenotation
+import collection.mutable
+import TreeTransforms.MiniPhaseTransform
+import dotty.tools.dotc.transform.TreeTransforms.TransformerInfo
+
+class Flatten extends MiniPhaseTransform with SymTransformer { thisTransform =>
+  import ast.tpd._
+  override def phaseName = "flatten"
+
+  def transformSym(ref: SymDenotation)(implicit ctx: Context) = {
+    if (ref.isClass && !ref.is(Package) && !ref.owner.is(Package)) {
+      ref.copySymDenotation(
+        name = ref.flatName,
+        owner = ref.enclosingPackageClass)
+    }
+    else ref
+  }
+
+  override def treeTransformPhase = thisTransform.next
+
+  private val liftedDefs = new mutable.ListBuffer[Tree]
+
+  private def liftIfNested(tree: Tree)(implicit ctx: Context, info: TransformerInfo) =
+    if (ctx.owner is Package) tree
+    else {
+      liftedDefs += transformFollowing(tree)
+      EmptyTree
+    }
+
+  override def transformStats(stats: List[Tree])(implicit ctx: Context, info: TransformerInfo) =
+    if (ctx.owner is Package) {
+      val liftedStats = stats ++ liftedDefs
+      liftedDefs.clear
+      liftedStats
+    }
+    else stats
+
+  override def transformTypeDef(tree: TypeDef)(implicit ctx: Context, info: TransformerInfo) =
+    liftIfNested(tree)
+}

src/dotty/tools/dotc/ElimLocals.scala renamed to src/dotty/tools/dotc/transform/ElimLocals.scala

@@ -5,6 +5,7 @@ import core._
 import Types._
 import Contexts._
 import Symbols._
+import SymDenotations._
 import Decorators._
 import Names._
 import StdNames._
@@ -13,7 +14,8 @@ import Flags._
 import language.implicitConversions
 
 object SymUtils {
-  implicit def decorateSymUtils(sym: Symbol): SymUtils = new SymUtils(sym)
+  implicit def decorateSymbol(sym: Symbol): SymUtils = new SymUtils(sym)
+  implicit def decorateSymDenot(d: SymDenotation): SymUtils = new SymUtils(d.symbol)
 }
 
 /** A decorator that provides methods on symbols
@@ -64,4 +66,7 @@ class SymUtils(val self: Symbol) extends AnyVal {
 
   def field(implicit ctx: Context): Symbol =
     self.owner.info.decl(self.asTerm.name.fieldName).suchThat(!_.is(Method)).symbol
+
+  /** `fullName` where `$' is the separator character */
+  def flatName(implicit ctx: Context): Name = self.fullNameSeparated('$')
 }

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

@@ -180,7 +180,7 @@ class TreeChecker {
     override def typedStats(trees: List[untpd.Tree], exprOwner: Symbol)(implicit ctx: Context): List[Tree] = {
       for (tree <- trees) tree match {
         case tree: untpd.DefTree => checkOwner(tree)
-        case _: untpd.Thicket => assert(false, "unexpanded thicket in statement sequence")
+        case _: untpd.Thicket => assert(false, i"unexpanded thicket $tree in statement sequence $trees%\n%")
         case _ =>
       }
       super.typedStats(trees, exprOwner)

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

@@ -15,7 +15,7 @@ class tests extends CompilerTest {
 
   implicit val defaultOptions = noCheckOptions ++ List(
       "-Yno-deep-subtypes",
-      "-Ycheck:patternMatcher,gettersSetters,lambdaLift"
+      "-Ycheck:patternMatcher,gettersSetters,flatten"
   )
 
   val twice = List("#runs", "2", "-YnoDoubleBindings")