Replace (Typing)Transformer with simple Traverser to avoid unnecessar…

…y tree copying

src/main/scala/com/softwaremill/guardedblocks/GuardedBlocksPlugin.scala

@@ -13,6 +13,4 @@ class GuardedBlocksPlugin(val global: Global) extends Plugin {
 
   override val components: List[PluginComponent] = List(new GuardedBlocksComponent(global))
 
-
-
 }

src/main/scala/com/softwaremill/guardedblocks/components/BlockTreesGuardian.scala

@@ -0,0 +1,25 @@
+package com.softwaremill.guardedblocks.components
+
+import scala.tools.nsc.Global
+
+class BlockTreesGuardian[G <: Global](val global: G) {
+  import global._
+
+  val guard: Tree => Unit = BlockTreesGuardianTraverser.traverse
+
+  private object BlockTreesGuardianTraverser extends Traverser {
+    override def traverse(tree: Tree): Unit = {
+      tree match {
+        case block@Block(stats, expr) =>
+          for {
+            stat <- stats.filter(_.tpe <:< block.tpe)
+          } global.reporter.error(stat.pos, s"Found unused statement!")
+        case _ =>
+      }
+      super.traverse(tree)
+    }
+  }
+
+}
+
+

src/main/scala/com/softwaremill/guardedblocks/components/GuardedBlocksComponent.scala

@@ -2,33 +2,19 @@ package com.softwaremill.guardedblocks.components
 
 import scala.tools.nsc._
 import scala.tools.nsc.plugins.PluginComponent
-import scala.tools.nsc.transform._
 
-class GuardedBlocksComponent(val global: Global) extends PluginComponent with Transform with TypingTransformers {
+class GuardedBlocksComponent(val global: Global) extends PluginComponent {
 
   import global._
 
   override val phaseName: String = "guardblocks"
-
   override def description: String = "check for unused statements in code blocks"
-
   override val runsAfter: List[String] = List("typer")
 
-  override protected def newTransformer(unit: CompilationUnit): Transformer =
-    new GuardedBlockTransformer(unit)
-
-  class GuardedBlockTransformer(unit: CompilationUnit) extends TypingTransformer(unit) {
-    override def transform(tree: Tree): Tree = {
-      tree match {
-        case block@Block(stats, expr) =>
-          for {
-            stat <- stats.filter(_.tpe <:< block.tpe)
-          } global.reporter.error(stat.pos, s"Found unused statement!")
-        case _ =>
-      }
-      super.transform(tree)
-    }
+  private val guardian = new BlockTreesGuardian[global.type](global)
 
+  override def newPhase(prev: Phase): Phase = new StdPhase(prev) {
+    override def apply(unit: CompilationUnit): Unit = guardian.guard(unit.body)
   }
 
 }