2 files changed, 25 insertions, 26 deletions
diff --git a/src/main/scala/Chisel/Core.scala b/src/main/scala/Chisel/Core.scala
index d9d7cf38..a3483c82 100644
--- a/src/main/scala/Chisel/Core.scala
+++ b/src/main/scala/Chisel/Core.scala
@@ -16,14 +16,6 @@ class IdGen {
 object Builder {
   val components = new ArrayBuffer[Component]()
   val idGen = new IdGen
-  val switchKeyz = new Stack[Stack[Bits]]()
-  def switchKeys = switchKeyz.top
-  def pushScope = {
-    switchKeyz.push(new Stack[Bits]())
-  }
-  def popScope = {
-    switchKeyz.pop()
-  }
   val modulez = new Stack[Module]()
   def pushModule(mod: Module) {
     modulez.push(mod)
@@ -993,7 +985,6 @@ object Module {
     val m = bc
     m.setRefs
     val cmd = popCommands
-    popScope
     popModule
     val ports = m.computePorts
     val component = Component(m.name, ports, cmd)
@@ -1017,7 +1008,6 @@ abstract class Module(_clock: Clock = null, _reset: Bool = null) extends Id {
   val name = globalNamespace.name(getClass.getName.split('.').last)
 
   pushModule(this)
-  pushScope
   pushCommands
 
   val params = Module.params
@@ -1091,11 +1081,9 @@ abstract class BlackBox(_clock: Clock = null, _reset: Bool = null) extends Modul
 
 object when {
   private[Chisel] def execBlock(block: => Unit): Command = {
-    pushScope
     pushCommands
     block
     val cmd = popCommands
-    popScope
     cmd
   }
   def apply(cond: => Bool)(block: => Unit): when = {
diff --git a/src/main/scala/Chisel/utils.scala b/src/main/scala/Chisel/utils.scala
index 1e024b11..6d073e3d 100644
--- a/src/main/scala/Chisel/utils.scala
+++ b/src/main/scala/Chisel/utils.scala
@@ -1,6 +1,10 @@
 package Chisel
 import Builder._
 import scala.math._
+import scala.language.reflectiveCalls
+import scala.language.experimental.macros
+import scala.reflect.runtime.universe._
+import scala.reflect.macros.whitebox._
 
 object log2Up
 {
@@ -122,23 +126,30 @@ object unless {
   }
 }
 
-object switch {
-  def apply(c: Bits)(block: => Unit) {
-    switchKeys.push(c)
-    block
-    switchKeys.pop()
+class SwitchContext[T <: Bits](cond: T) {
+  def is(v: Iterable[T])(block: => Unit) {
+    if (!v.isEmpty) when (v.map(_.asUInt === cond.asUInt).reduce(_||_)) { block }
   }
+  def is(v: T)(block: => Unit) { is(Seq(v))(block) }
+  def is(v: T, vr: T*)(block: => Unit) { is(v :: vr.toList)(block) }
+}
+
+object is { // Begin deprecation of non-type-parameterized is statements.
+  def apply(v: Iterable[Bits])(block: => Unit) { ChiselError.error("The 'is' keyword may not be used outside of a switch.") }
+  def apply(v: Bits)(block: => Unit) { ChiselError.error("The 'is' keyword may not be used outside of a switch.") }
+  def apply(v: Bits, vr: Bits*)(block: => Unit) { ChiselError.error("The 'is' keyword may not be used outside of a switch.") }
 }
 
-object is {
-  def apply(v: Bits)(block: => Unit): Unit =
-    apply(Seq(v))(block)
-  def apply(v: Bits, vr: Bits*)(block: => Unit): Unit =
-    apply(v :: vr.toList)(block)
-  def apply(v: Iterable[Bits])(block: => Unit): Unit = {
-    val keys = switchKeys
-    if (keys.isEmpty) ChiselError.error("The 'is' keyword may not be used outside of a switch.")
-    else if (!v.isEmpty) when (v.map(_.toBits === keys.top.toBits).reduce(_||_)) { block }
+object switch {
+  def apply[T <: Bits](cond: T)(x: => Unit): Unit = macro impl
+  def impl(c: Context)(cond: c.Tree)(x: c.Tree) = { import c.universe._
+    def extractIsStatement(tree: Tree): List[c.universe.Tree] = tree match {
+      case q"Chisel.is.apply( ..$params )( ..$body )" => List(q"sc.is( ..$params )( ..$body )")
+      case b => throw new Exception(s"Cannot include blocks that do not begin with is() in switch.")
+    }
+    val q"..$body" = x
+    val ises = body.flatMap(extractIsStatement(_))
+    q"""{ val sc = new SwitchContext($cond); ..$ises }"""
   }
 }