Make CapturedVars a functional transform.

No global side effect on capturedVars anymore.

1 files changed, 72 insertions, 69 deletions

diff --git a/src/dotty/tools/dotc/transform/CapturedVars.scala b/src/dotty/tools/dotc/transform/CapturedVars.scala
index b2118d3ec..14bb4a738 100644
--- a/src/dotty/tools/dotc/transform/CapturedVars.scala
+++ b/src/dotty/tools/dotc/transform/CapturedVars.scala
@@ -17,91 +17,94 @@ import SymUtils._
 import collection.{ mutable, immutable }
 import collection.mutable.{ LinkedHashMap, LinkedHashSet, TreeSet }
 
-class CapturedVars extends MiniPhaseTransform with IdentityDenotTransformer { thisTransform =>
+class CapturedVars extends MiniPhase with IdentityDenotTransformer { thisTransform =>
   import ast.tpd._
 
   /** the following two members override abstract members in Transform */
   val phaseName: String = "capturedVars"
+  val treeTransform = new Transform(Set())
 
-  override def treeTransformPhase = thisTransform.next
+  class Transform(captured: collection.Set[Symbol]) extends TreeTransform {
+    def phase = thisTransform
+    override def treeTransformPhase = thisTransform.next
 
-  private var captured: mutable.HashSet[Symbol] = _
-
-  private class CollectCaptured(implicit ctx: Context) extends EnclosingMethodTraverser {
-    def traverse(enclMeth: Symbol, tree: Tree) = tree match {
-      case id: Ident =>
-        val sym = id.symbol
-        if (sym.is(Mutable, butNot = Method) && sym.owner.isTerm && sym.enclosingMethod != enclMeth) {
-          ctx.log(i"capturing $sym in ${sym.enclosingMethod}, referenced from $enclMeth")
-          captured += sym
-        }
-      case _ =>
-        foldOver(enclMeth, tree)
-    }
-    def runOver(tree: Tree) = {
-      captured = mutable.HashSet()
-      apply(NoSymbol, tree)
+    private class CollectCaptured(implicit ctx: Context) extends EnclosingMethodTraverser {
+      private val captured = mutable.HashSet[Symbol]()
+      def traverse(enclMeth: Symbol, tree: Tree) = tree match {
+        case id: Ident =>
+          val sym = id.symbol
+          if (sym.is(Mutable, butNot = Method) && sym.owner.isTerm && sym.enclosingMethod != enclMeth) {
+            ctx.log(i"capturing $sym in ${sym.enclosingMethod}, referenced from $enclMeth")
+            captured += sym
+          }
+        case _ =>
+          foldOver(enclMeth, tree)
+      }
+      def runOver(tree: Tree): collection.Set[Symbol] = {
+        apply(NoSymbol, tree)
+        captured
+      }
     }
-  }
 
-  override def prepareForUnit(tree: Tree)(implicit ctx: Context) = {
-    (new CollectCaptured)(ctx.withPhase(thisTransform)).runOver(ctx.compilationUnit.tpdTree)
-    this
-  }
+    override def prepareForUnit(tree: Tree)(implicit ctx: Context) = {
+      val captured = (new CollectCaptured)(ctx.withPhase(thisTransform))
+        .runOver(ctx.compilationUnit.tpdTree)
+      new Transform(captured)
+    }
 
-  /** The {Volatile|}{Int|Double|...|Object}Ref class corresponding to the class `cls`,
-   *  depending on whether the reference should be @volatile
-   */
-  def refCls(cls: Symbol, isVolatile: Boolean)(implicit ctx: Context): Symbol = {
-    val refMap = if (isVolatile) defn.volatileRefClass else defn.refClass
-    refMap.getOrElse(cls, refMap(defn.ObjectClass))
-  }
+    /** The {Volatile|}{Int|Double|...|Object}Ref class corresponding to the class `cls`,
+     *  depending on whether the reference should be @volatile
+     */
+    def refCls(cls: Symbol, isVolatile: Boolean)(implicit ctx: Context): Symbol = {
+      val refMap = if (isVolatile) defn.volatileRefClass else defn.refClass
+      refMap.getOrElse(cls, refMap(defn.ObjectClass))
+    }
 
-  def capturedType(vble: Symbol)(implicit ctx: Context): Type = {
-    val oldInfo = vble.denot(ctx.withPhase(thisTransform)).info
-    refCls(oldInfo.classSymbol, vble.isVolatile).typeRef
-  }
+    def capturedType(vble: Symbol)(implicit ctx: Context): Type = {
+      val oldInfo = vble.denot(ctx.withPhase(thisTransform)).info
+      refCls(oldInfo.classSymbol, vble.isVolatile).typeRef
+    }
 
-  override def prepareForValDef(vdef: ValDef)(implicit ctx: Context) = {
-    val sym = vdef.symbol
-    if (captured contains sym) {
-      val newd = sym.denot(ctx.withPhase(thisTransform)).copySymDenotation(
-        info = refCls(sym.info.classSymbol, sym.hasAnnotation(defn.VolatileAnnot)).typeRef)
-      newd.removeAnnotation(defn.VolatileAnnot)
-      newd.installAfter(thisTransform)
+    override def prepareForValDef(vdef: ValDef)(implicit ctx: Context) = {
+      val sym = vdef.symbol
+      if (captured contains sym) {
+        val newd = sym.denot(ctx.withPhase(thisTransform)).copySymDenotation(
+          info = refCls(sym.info.classSymbol, sym.hasAnnotation(defn.VolatileAnnot)).typeRef)
+        newd.removeAnnotation(defn.VolatileAnnot)
+        newd.installAfter(thisTransform)
+      }
+      this
     }
-    this
-  }
 
-  override def transformValDef(vdef: ValDef)(implicit ctx: Context, info: TransformerInfo): Tree = {
-    val vble = vdef.symbol
-    if (captured contains vble) {
-      def boxMethod(name: TermName): Tree =
-        ref(vble.info.classSymbol.companionModule.info.member(name).symbol)
-      cpy.ValDef(vdef)(
-        rhs = vdef.rhs match {
-          case EmptyTree => boxMethod(nme.zero).appliedToNone.withPos(vdef.pos)
-          case arg       => boxMethod(nme.create).appliedTo(arg)
-        },
-        tpt = TypeTree(vble.info).withPos(vdef.tpt.pos))
+    override def transformValDef(vdef: ValDef)(implicit ctx: Context, info: TransformerInfo): Tree = {
+      val vble = vdef.symbol
+      if (captured contains vble) {
+        def boxMethod(name: TermName): Tree =
+          ref(vble.info.classSymbol.companionModule.info.member(name).symbol)
+        cpy.ValDef(vdef)(
+          rhs = vdef.rhs match {
+            case EmptyTree => boxMethod(nme.zero).appliedToNone.withPos(vdef.pos)
+            case arg => boxMethod(nme.create).appliedTo(arg)
+          },
+          tpt = TypeTree(vble.info).withPos(vdef.tpt.pos))
+      } else vdef
     }
-    else vdef
-  }
 
-  override def transformIdent(id: Ident)(implicit ctx: Context, info: TransformerInfo): Tree = {
-    val vble = id.symbol
-    if (captured(vble))
-      (id select nme.elem).ensureConforms(vble.denot(ctx.withPhase(thisTransform)).info)
-    else id
-  }
+    override def transformIdent(id: Ident)(implicit ctx: Context, info: TransformerInfo): Tree = {
+      val vble = id.symbol
+      if (captured(vble))
+        (id select nme.elem).ensureConforms(vble.denot(ctx.withPhase(thisTransform)).info)
+      else id
+    }
 
-  override def transformAssign(tree: Assign)(implicit ctx: Context, info: TransformerInfo): Tree = {
-    val lhs1 = tree.lhs match {
-      case TypeApply(Select(qual @ Select(qual2, nme.elem), nme.asInstanceOf_), _) =>
-        assert(captured(qual2.symbol))
-        qual
-      case _ => tree.lhs
+    override def transformAssign(tree: Assign)(implicit ctx: Context, info: TransformerInfo): Tree = {
+      val lhs1 = tree.lhs match {
+        case TypeApply(Select(qual @ Select(qual2, nme.elem), nme.asInstanceOf_), _) =>
+          assert(captured(qual2.symbol))
+          qual
+        case _ => tree.lhs
+      }
+      cpy.Assign(tree)(lhs1, tree.rhs)
     }
-    cpy.Assign(tree)(lhs1, tree.rhs)
   }
 }
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