RawModule with no reset should be able to use withClock method. (#1065)

* RawModule with no reset should be able to use withClock method.
- refactor ClockAndReset
  - now has `clockOpt: Option[Clock]` and `resetOpt: Option[Reset]` constructor params
  - convenience methods clock and reset tries to deref the option
  - ClockAndReset.empty is factory method for (None, None)
- In Builder
  - forcedClock does not check resetOpt now
  - forcedReset does not check clockOpt now
- withClock no longer looks at resetOpt
- withReset no longer looks at clockOpt
- Module starts with empty ClockAndReset

* RawModule with no reset should be able to use withClock method.
Refactor again based on @ducky64 comments
- refactor away ClockAndReset, now builder just has a
  - currentClock
  - currentReset
- withClock, withRest, withClockAndReset just use these fields directly

* RawModule with no reset should be able to use withClock method.
- Fixed typo in withReset handler, now picks up new reset

4 files changed, 54 insertions, 27 deletions

diff --git a/chiselFrontend/src/main/scala/chisel3/core/Module.scala b/chiselFrontend/src/main/scala/chisel3/core/Module.scala
index f97d51ac..5cd48a6a 100644
--- a/chiselFrontend/src/main/scala/chisel3/core/Module.scala
+++ b/chiselFrontend/src/main/scala/chisel3/core/Module.scala
@@ -41,8 +41,9 @@ object Module extends SourceInfoDoc {
     val whenDepth: Int = Builder.whenDepth
 
     // Save then clear clock and reset to prevent leaking scope, must be set again in the Module
-    val clockAndReset: Option[ClockAndReset] = Builder.currentClockAndReset
-    Builder.currentClockAndReset = None
+    val (saveClock, saveReset)  = (Builder.currentClock, Builder.currentReset)
+    Builder.currentClock = None
+    Builder.currentReset = None
 
     // Execute the module, this has the following side effects:
     //   - set currentModule
@@ -59,9 +60,10 @@ object Module extends SourceInfoDoc {
                      "This is probably due to rewrapping a Module instance with Module()." +
                      sourceInfo.makeMessage(" See " + _))
     }
-    Builder.currentModule = parent // Back to parent!
+    Builder.currentModule = parent     // Back to parent!
     Builder.whenDepth = whenDepth
-    Builder.currentClockAndReset = clockAndReset // Back to clock and reset scope
+    Builder.currentClock = saveClock   // Back to clock and reset scope
+    Builder.currentReset = saveReset
 
     val component = module.generateComponent()
     Builder.components += component
diff --git a/chiselFrontend/src/main/scala/chisel3/core/MultiClock.scala b/chiselFrontend/src/main/scala/chisel3/core/MultiClock.scala
index 6af4da41..aaa03d78 100644
--- a/chiselFrontend/src/main/scala/chisel3/core/MultiClock.scala
+++ b/chiselFrontend/src/main/scala/chisel3/core/MultiClock.scala
@@ -2,14 +2,9 @@
 
 package chisel3.core
 
-import scala.language.experimental.macros
-
 import chisel3.internal._
-import chisel3.internal.Builder.pushCommand
-import chisel3.internal.firrtl._
-import chisel3.internal.sourceinfo.{SourceInfo}
 
-private[chisel3] final case class ClockAndReset(clock: Clock, reset: Reset)
+import scala.language.experimental.macros
 
 object withClockAndReset {  // scalastyle:ignore object.name
   /** Creates a new Clock and Reset scope
@@ -21,11 +16,17 @@ object withClockAndReset {  // scalastyle:ignore object.name
     */
   def apply[T](clock: Clock, reset: Reset)(block: => T): T = {
     // Save parentScope
-    val parentScope = Builder.currentClockAndReset
-    Builder.currentClockAndReset = Some(ClockAndReset(clock, reset))
+    val parentClock = Builder.currentClock
+    val parentReset = Builder.currentReset
+
+    Builder.currentClock = Some(clock)
+    Builder.currentReset = Some(reset)
+
     val res = block // execute block
+
     // Return to old scope
-    Builder.currentClockAndReset = parentScope
+    Builder.currentClock = parentClock
+    Builder.currentReset = parentReset
     res
   }
 }
@@ -37,8 +38,15 @@ object withClock {  // scalastyle:ignore object.name
     * @param block the block of code to run with new implicit Clock
     * @return the result of the block
     */
-  def apply[T](clock: Clock)(block: => T): T =
-    withClockAndReset(clock, Module.reset)(block)
+  def apply[T](clock: Clock)(block: => T): T =  {
+    // Save parentScope
+    val parentClock = Builder.currentClock
+    Builder.currentClock = Some(clock)
+    val res = block // execute block
+    // Return to old scope
+    Builder.currentClock = parentClock
+    res
+  }
 }
 
 object withReset {  // scalastyle:ignore object.name
@@ -48,7 +56,15 @@ object withReset {  // scalastyle:ignore object.name
     * @param block the block of code to run with new implicit Reset
     * @return the result of the block
     */
-  def apply[T](reset: Reset)(block: => T): T =
-    withClockAndReset(Module.clock, reset)(block)
+  def apply[T](reset: Reset)(block: => T): T = {
+    // Save parentScope
+    val parentReset = Builder.currentReset
+    Builder.currentReset = Some(reset)
+    val res = block // execute block
+    // Return to old scope
+    Builder.currentReset = parentReset
+    res
+  }
+
 }
 
diff --git a/chiselFrontend/src/main/scala/chisel3/core/RawModule.scala b/chiselFrontend/src/main/scala/chisel3/core/RawModule.scala
index 397debcb..b224d9a3 100644
--- a/chiselFrontend/src/main/scala/chisel3/core/RawModule.scala
+++ b/chiselFrontend/src/main/scala/chisel3/core/RawModule.scala
@@ -146,7 +146,8 @@ abstract class MultiIOModule(implicit moduleCompileOptions: CompileOptions)
   val reset: Reset = IO(Input(Bool()))
 
   // Setup ClockAndReset
-  Builder.currentClockAndReset = Some(ClockAndReset(clock, reset))
+  Builder.currentClock = Some(clock)
+  Builder.currentReset = Some(reset)
 
   private[core] override def initializeInParent(parentCompileOptions: CompileOptions): Unit = {
     implicit val sourceInfo = UnlocatableSourceInfo
diff --git a/chiselFrontend/src/main/scala/chisel3/internal/Builder.scala b/chiselFrontend/src/main/scala/chisel3/internal/Builder.scala
index 1163171c..d825f39d 100644
--- a/chiselFrontend/src/main/scala/chisel3/internal/Builder.scala
+++ b/chiselFrontend/src/main/scala/chisel3/internal/Builder.scala
@@ -183,11 +183,13 @@ private[chisel3] class DynamicContext() {
   // Used to distinguish between no Module() wrapping, multiple wrappings, and rewrapping
   var readyForModuleConstr: Boolean = false
   var whenDepth: Int = 0 // Depth of when nesting
-  var currentClockAndReset: Option[ClockAndReset] = None
+  var currentClock: Option[Clock] = None
+  var currentReset: Option[Reset] = None
   val errors = new ErrorLog
   val namingStack = new internal.naming.NamingStack
 }
 
+//scalastyle:off number.of.methods
 private[chisel3] object Builder {
   // All global mutable state must be referenced via dynamicContextVar!!
   private val dynamicContextVar = new DynamicVariable[Option[DynamicContext]](None)
@@ -248,16 +250,22 @@ private[chisel3] object Builder {
   def whenDepth_=(target: Int): Unit = {
     dynamicContext.whenDepth = target
   }
-  def currentClockAndReset: Option[ClockAndReset] = dynamicContext.currentClockAndReset
-  def currentClockAndReset_=(target: Option[ClockAndReset]): Unit = {
-    dynamicContext.currentClockAndReset = target
+  def currentClock: Option[Clock] = dynamicContext.currentClock
+  def currentClock_=(newClock: Option[Clock]): Unit = {
+    dynamicContext.currentClock = newClock
   }
-  def forcedClockAndReset: ClockAndReset = currentClockAndReset match {
-    case Some(clockAndReset) => clockAndReset
-    case None => throwException("Error: No implicit clock and reset.")
+
+  def currentReset: Option[Reset] = dynamicContext.currentReset
+  def currentReset_=(newReset: Option[Reset]): Unit = {
+    dynamicContext.currentReset = newReset
   }
-  def forcedClock: Clock = forcedClockAndReset.clock
-  def forcedReset: Reset = forcedClockAndReset.reset
+
+  def forcedClock: Clock = currentClock.getOrElse(
+    throwException("Error: No implicit clock.")
+  )
+  def forcedReset: Reset = currentReset.getOrElse(
+    throwException("Error: No implicit reset.")
+  )
 
   // TODO(twigg): Ideally, binding checks and new bindings would all occur here
   // However, rest of frontend can't support this yet.