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diff --git a/src/main/scala/chisel3/util/Conditional.scala b/src/main/scala/chisel3/util/Conditional.scala
new file mode 100644
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+++ b/src/main/scala/chisel3/util/Conditional.scala
@@ -0,0 +1,94 @@
+// See LICENSE for license details.
+
+/** Conditional blocks.
+  */
+
+package chisel3.util
+
+import scala.language.reflectiveCalls
+import scala.language.experimental.macros
+import scala.reflect.runtime.universe._
+import scala.reflect.macros.blackbox._
+
+import chisel3._
+
+object unless {  // scalastyle:ignore object.name
+  /** Does the same thing as [[when$ when]], but with the condition inverted.
+    */
+  def apply(c: Bool)(block: => Unit) {
+    when (!c) { block }
+  }
+}
+
+/** Implementation details for [[switch]]. See [[switch]] and [[chisel3.util.is is]] for the
+  * user-facing API.
+  */
+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) }
+}
+
+/** Use to specify cases in a [[switch]] block, equivalent to a [[when$ when]] block comparing to
+  * the condition variable.
+  *
+  * @note illegal outside a [[switch]] block
+  * @note multiple conditions may fire simultaneously
+  * @note dummy implementation, a macro inside [[switch]] transforms this into the actual
+  * implementation
+  */
+object is {   // scalastyle:ignore object.name
+  // TODO: Begin deprecation of non-type-parameterized is statements.
+  /** Executes `block` if the switch condition is equal to any of the values in `v`.
+    */
+  def apply(v: Iterable[Bits])(block: => Unit) {
+    require(false, "The 'is' keyword may not be used outside of a switch.")
+  }
+
+  /** Executes `block` if the switch condition is equal to `v`.
+    */
+  def apply(v: Bits)(block: => Unit) {
+    require(false, "The 'is' keyword may not be used outside of a switch.")
+  }
+
+  /** Executes `block` if the switch condition is equal to any of the values in the argument list.
+    */
+  def apply(v: Bits, vr: Bits*)(block: => Unit) {
+    require(false, "The 'is' keyword may not be used outside of a switch.")
+  }
+}
+
+/** Conditional logic to form a switch block. See [[is$ is]] for the case API.
+  *
+  * @example {{{
+  * switch (myState) {
+  *   is (state1) {
+  *     // some logic here that runs when myState === state1
+  *   }
+  *   is (state2) {
+  *     // some logic here that runs when myState === state2
+  *   }
+  * }
+  * }}}
+  */
+object switch {  // scalastyle:ignore object.name
+  def apply[T <: Bits](cond: T)(x: => Unit): Unit = macro impl
+  def impl(c: Context)(cond: c.Tree)(x: c.Tree): c.Tree = { import c.universe._
+    val sc = c.universe.internal.reificationSupport.freshTermName("sc")
+    def extractIsStatement(tree: Tree): List[c.universe.Tree] = tree match {
+      // TODO: remove when Chisel compatibility package is removed
+      case q"Chisel.`package`.is.apply( ..$params )( ..$body )" => List(q"$sc.is( ..$params )( ..$body )")
+      case q"chisel3.util.is.apply( ..$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 }"""
+  }
+}