Added methods to prepare-for and transform a complete compilation unit tree.

Should replace destructive inits.

Author: odersky

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

@@ -92,6 +92,8 @@ object TreeTransforms {
     def prepareForPackageDef(tree: PackageDef)(implicit ctx: Context) = this
     def prepareForStats(trees: List[Tree])(implicit ctx: Context) = this
 
+    def prepareForUnit(tree: Tree)(implicit ctx: Context) = this
+
     def transformIdent(tree: Ident)(implicit ctx: Context, info: TransformerInfo): Tree = tree
     def transformSelect(tree: Select)(implicit ctx: Context, info: TransformerInfo): Tree = tree
     def transformThis(tree: This)(implicit ctx: Context, info: TransformerInfo): Tree = tree
@@ -125,6 +127,8 @@ object TreeTransforms {
     def transformStats(trees: List[Tree])(implicit ctx: Context, info: TransformerInfo): List[Tree] = trees
     def transformOther(tree: Tree)(implicit ctx: Context, info: TransformerInfo): Tree = tree
 
+    def transformUnit(tree: Tree)(implicit ctx: Context, info: TransformerInfo): Tree = tree
+
     /** Transform tree using all transforms of current group (including this one) */
     def transform(tree: Tree)(implicit ctx: Context, info: TransformerInfo): Tree = info.group.transform(tree, info, 0)
 
@@ -273,6 +277,7 @@ object TreeTransforms {
       nxPrepTemplate = index(transformations, "prepareForTemplate")
       nxPrepPackageDef = index(transformations, "prepareForPackageDef")
       nxPrepStats = index(transformations, "prepareForStats")
+      nxPrepUnit = index(transformations, "prepareForUnit")
 
       nxTransIdent = index(transformations, "transformIdent")
       nxTransSelect = index(transformations, "transformSelect")
@@ -305,6 +310,7 @@ object TreeTransforms {
       nxTransTemplate = index(transformations, "transformTemplate")
       nxTransPackageDef = index(transformations, "transformPackageDef")
       nxTransStats = index(transformations, "transformStats")
+      nxTransUnit = index(transformations, "transformUnit")
       nxTransOther = index(transformations, "transformOther")
     }
 
@@ -412,6 +418,7 @@ object TreeTransforms {
     var nxPrepTemplate: Array[Int] = _
     var nxPrepPackageDef: Array[Int] = _
     var nxPrepStats: Array[Int] = _
+    var nxPrepUnit: Array[Int] = _
 
     var nxTransIdent: Array[Int] = _
     var nxTransSelect: Array[Int] = _
@@ -444,6 +451,7 @@ object TreeTransforms {
     var nxTransTemplate: Array[Int] = _
     var nxTransPackageDef: Array[Int] = _
     var nxTransStats: Array[Int] = _
+    var nxTransUnit: Array[Int] = _
     var nxTransOther: Array[Int] = _
   }
 
@@ -454,7 +462,7 @@ object TreeTransforms {
 
     override def run(implicit ctx: Context): Unit = {
       val curTree = ctx.compilationUnit.tpdTree
-      val newTree = transform(curTree)
+      val newTree = macroTransform(curTree)
       ctx.compilationUnit.tpdTree = newTree
     }
 
@@ -517,16 +525,19 @@ object TreeTransforms {
     val prepForTemplate: Mutator[Template] = (trans, tree, ctx) => trans.prepareForTemplate(tree)(ctx)
     val prepForPackageDef: Mutator[PackageDef] = (trans, tree, ctx) => trans.prepareForPackageDef(tree)(ctx)
     val prepForStats: Mutator[List[Tree]] = (trans, trees, ctx) => trans.prepareForStats(trees)(ctx)
+    val prepForUnit: Mutator[Tree] = (trans, tree, ctx) => trans.prepareForUnit(tree)(ctx)
 
-    def transform(t: Tree)(implicit ctx: Context): Tree = {
+    def macroTransform(t: Tree)(implicit ctx: Context): Tree = {
       val initialTransformations = transformations
       val info = new TransformerInfo(initialTransformations, new NXTransformations(initialTransformations), this)
       initialTransformations.zipWithIndex.foreach {
         case (transform, id) =>
           transform.idx = id
           transform.init(ctx, info)
       }
-      transform(t, info, 0)
+      implicit val mutatedInfo: TransformerInfo = mutateTransformers(info, prepForUnit, info.nx.nxPrepUnit, t, 0)
+      if (mutatedInfo eq null) t
+      else goUnit(transform(t, mutatedInfo, 0), mutatedInfo.nx.nxTransUnit(0))
     }
 
     @tailrec
@@ -859,6 +870,15 @@ object TreeTransforms {
       } else tree
     }
 
+    @tailrec
+    final private[TreeTransforms] def goUnit(tree: Tree, cur: Int)(implicit ctx: Context, info: TransformerInfo): Tree = {
+      if (cur < info.transformers.length) {
+        val trans = info.transformers(cur)
+        val t = trans.transformUnit(tree)(ctx.withPhase(trans.treeTransformPhase), info)
+        goUnit(t, info.nx.nxTransUnit(cur + 1))
+      } else tree
+    }
+
     final private[TreeTransforms] def goOther(tree: Tree, cur: Int)(implicit ctx: Context, info: TransformerInfo): Tree = {
       if (cur < info.transformers.length) {
         val trans = info.transformers(cur)
@@ -1219,5 +1239,4 @@ object TreeTransforms {
     def transformSubTrees[Tr <: Tree](trees: List[Tr], info: TransformerInfo, current: Int)(implicit ctx: Context): List[Tr] =
       transformTrees(trees, info, current)(ctx).asInstanceOf[List[Tr]]
   }
-
 }

test/test/transform/TreeTransformerTest.scala

@@ -24,7 +24,7 @@ class TreeTransformerTest extends DottyTest {
 
         override def phaseName: String = "test"
       }
-      val transformed = transformer.transform(tree)
+      val transformed = transformer.macroTransform(tree)
 
       Assert.assertTrue("returns same tree if unmodified",
         tree eq transformed
@@ -46,7 +46,7 @@ class TreeTransformerTest extends DottyTest {
 
         override def phaseName: String = "test"
       }
-      val transformed = transformer.transform(tree)
+      val transformed = transformer.macroTransform(tree)
 
       Assert.assertTrue("returns same tree if unmodified",
         transformed.toString.contains("List(ValDef(Modifiers(,,List()),d,TypeTree[TypeRef(ThisType(module class scala),Int)],Literal(Constant(2)))")
@@ -77,7 +77,7 @@ class TreeTransformerTest extends DottyTest {
         override def phaseName: String = "test"
 
       }
-      val tr = transformer.transform(tree).toString
+      val tr = transformer.macroTransform(tree).toString
 
       Assert.assertTrue("node can rewrite children",
         tr.contains("Literal(Constant(2))") && !tr.contains("Literal(Constant(-1))")
@@ -123,7 +123,7 @@ class TreeTransformerTest extends DottyTest {
 
         override def phaseName: String = "test"
       }
-      val tr = transformer.transform(tree).toString
+      val tr = transformer.macroTransform(tree).toString
 
       Assert.assertTrue("node can rewrite children",
         tr.contains("Literal(Constant(3))")
@@ -191,7 +191,7 @@ class TreeTransformerTest extends DottyTest {
 
         override def phaseName: String = "test"
       }
-      val tr = transformer.transform(tree).toString
+      val tr = transformer.macroTransform(tree).toString
       Assert.assertTrue("transformations aren't invoked multiple times",
         transformed1 == 2 && transformed2 == 3
       )