Repackagecore rebase (#1078)

* Move Bits, Data, and BitPat to chiselFrontend/src/main/scala/chisel3
 and deal with the subsequent fallout.

* Move Aggregate, Clock, Mem, Printf, Reg

* Move almost all chisel3.core definitions to chisel3 or chisel3.experimental

* Revive core package object to provide aliases for moved definitions.

* Cleanup package definitions; eliminate ambiguous implicits

* Move more definitions to experimental.
Extract BaseModule, DataMirror, ExtModule, IO into their own files.

* Put BitPat back in chisel3.util

* More experimental motion - avoid multiple import definitions.

* Add experimental.FixedPoint alias

* Add EnumType definition to core package.
Update deprecated messages to refer to correct object

* Move FixedPoint into the experimental package (but keep it in Bits.scala).

* Add missing implicits to core/package - compatibility

* Cleanup: update ScalaDoc references; remove unused imports

* Add Reset alias to core/package

* Use common 3.2 version in deprecation warning

* Move Binding from core to internal.

* Optimize imports.

* Repair IntelliJ's overly cleanliness.

* Move Bits, Data, and BitPat to chiselFrontend/src/main/scala/chisel3
 and deal with the subsequent fallout.

Move Aggregate, Clock, Mem, Printf, Reg

Move almost all chisel3.core definitions to chisel3 or chisel3.experimental

Revive core package object to provide aliases for moved definitions.

Cleanup package definitions; eliminate ambiguous implicits

Move more definitions to experimental.
Extract BaseModule, DataMirror, ExtModule, IO into their own files.

Add EnumType definition to core package.
Update deprecated messages to refer to correct object

Move FixedPoint into the experimental package (but keep it in Bits.scala).

Add missing implicits to core/package - compatibility

Cleanup: update ScalaDoc references; remove unused imports

Use common 3.2 version in deprecation warning

Move Binding from core to internal.

* Change == to reference equality (eq) in Data print (#1044)

* Remove @chiselName from MixedVec (#1045)

* Fix enum annotations (#936)

* Turned off strong enum annotations because they weren't working with Vec
indexes
* Add new EnumVecAnnotation for vecs of enums and vecs of bundles with
enum fields
* Changed Clock's width parameter back to a fixed constant value of 1
* Fixed enum annotations for Vecs of Bundles which contain enum elements
* Fixed usage of "when/otherwise" to use consistent style

* Add Record to type hierarchy documentation

* Undeprecate isLit (#1048)

* move doNotDedup to experimental (#1008)

* Aggregate coverage - aggregate tests but not publishing (#1040)

Discover a working combination of aggregate usage to enable coverage of subproject testing but publish a single Jar.
Use "scalastyle-test-config.xml" for scalastyle config in tests.
Enable "_" in method names and accept method names ending in "_=".
Re-sync scalastyle-test-config.xml with scalastyle-config.xml
This should finally fix #772.

* Check field referential equality in autoclonetype (#1047)

* Allow naming annotation to work outside builder context (#1051)

* Try to eliminate JVM hang due to static initialization deadlock (#1053)

* Make core.DontCare private to chisel3 (#1054)

Force clients to access 'DontCare' through the chisel3 package to ensure it's created as a chisel3 object and not a client object.

* Ignore empty aggregates elements when binding aggregate direction (#946)

Previously, including an empty aggregate in a Bundle would cause
a MixedDirectionAggregateException because it has no elements and thus
doesn't have a direction

* Add SampleElementBinding for Vec sample elements
* Add ActualDirection.Empty for bound empty aggregates

* Detect bundle aliasing (#1050)

* Implement connectFromBits in ChiselEnum (#1052)

This is necessary to use ChiselEnum in aggregates where things are
casted using .asTypeOf

* Optimize imports.

* Move Analog to experimental.

* More repackage cleanup - reduce differences with master.

* Cleanup chisel3 references.

* More chisel3 reference cleanup.

* Merge cleanup.

* Remove unused import

* Bump core deprecation to 3.3

* Move DontCare back into Data.scala inside package internal

* Re-indent experimental/internal package code

* Move code back to original files - facilitate comparison with other branches

* Some code motion, update imports, minimize master differences
Move exceptions up to chisel3 package object - they're part of the interface.

* More master diff minimization.

* Try to eliminate JVM hang due to static initialization deadlock (#1053)

* Ignore empty aggregates elements when binding aggregate direction (#946)

Previously, including an empty aggregate in a Bundle would cause
a MixedDirectionAggregateException because it has no elements and thus
doesn't have a direction

* Add SampleElementBinding for Vec sample elements
* Add ActualDirection.Empty for bound empty aggregates

* Implement connectFromBits in ChiselEnum (#1052)

This is necessary to use ChiselEnum in aggregates where things are
casted using .asTypeOf

* Move Analog to experimental.

More repackage cleanup - reduce differences with master.

Cleanup chisel3 references.

More chisel3 reference cleanup.

* Fix wrong directionality for Vec(Flipped())

Create Chisel IR Port() in a way that Converter is happy with.
Also add more extensive test suite for future-proofing.

Close #1063

* Move Bits, Data, and BitPat to chiselFrontend/src/main/scala/chisel3
 and deal with the subsequent fallout.

Move Aggregate, Clock, Mem, Printf, Reg

Move almost all chisel3.core definitions to chisel3 or chisel3.experimental

Revive core package object to provide aliases for moved definitions.

Cleanup package definitions; eliminate ambiguous implicits

Move more definitions to experimental.
Extract BaseModule, DataMirror, ExtModule, IO into their own files.

Put BitPat back in chisel3.util

More experimental motion - avoid multiple import definitions.

Add experimental.FixedPoint alias

Add EnumType definition to core package.
Update deprecated messages to refer to correct object

Move FixedPoint into the experimental package (but keep it in Bits.scala).

Add missing implicits to core/package - compatibility

Cleanup: update ScalaDoc references; remove unused imports

Add Reset alias to core/package

Use common 3.2 version in deprecation warning

Move Binding from core to internal.

Optimize imports.

Repair IntelliJ's overly cleanliness.

Move Bits, Data, and BitPat to chiselFrontend/src/main/scala/chisel3
 and deal with the subsequent fallout.

Move Aggregate, Clock, Mem, Printf, Reg

Move almost all chisel3.core definitions to chisel3 or chisel3.experimental

Revive core package object to provide aliases for moved definitions.

Cleanup package definitions; eliminate ambiguous implicits

Move more definitions to experimental.
Extract BaseModule, DataMirror, ExtModule, IO into their own files.

Add EnumType definition to core package.
Update deprecated messages to refer to correct object

Move FixedPoint into the experimental package (but keep it in Bits.scala).

Add missing implicits to core/package - compatibility

Cleanup: update ScalaDoc references; remove unused imports

Use common 3.2 version in deprecation warning

Move Binding from core to internal.

Optimize imports.

Merge cleanup.

Remove unused import

Bump core deprecation to 3.3

Move DontCare back into Data.scala inside package internal

Re-indent experimental/internal package code

Move code back to original files - facilitate comparison with other branches

Some code motion, update imports, minimize master differences
Move exceptions up to chisel3 package object - they're part of the interface.

More master diff minimization.

Fix minor discrepancies with repackagecore-testbed

* Remove redundant imports
As part of its import updating process, IntelliJ converted some import statements to `import package.{object, _}`. Is this intended to show an explicit dependency on `package.object` and a further dependency on `package` implicits? Unsure. Replace these with `import package._`

* Move the BaseModule object into the internal package.

6 files changed, 700 insertions, 17 deletions

diff --git a/chiselFrontend/src/main/scala/chisel3/internal/BiConnect.scala b/chiselFrontend/src/main/scala/chisel3/internal/BiConnect.scala
new file mode 100644
index 00000000..e122f13a
--- /dev/null
+++ b/chiselFrontend/src/main/scala/chisel3/internal/BiConnect.scala
@@ -0,0 +1,332 @@
+// See LICENSE for license details.
+
+package chisel3.internal
+
+import chisel3._
+import chisel3.experimental.{Analog, BaseModule, RawModule, attach}
+import chisel3.internal.Builder.pushCommand
+import chisel3.internal.firrtl.{Connect, DefInvalid}
+import scala.language.experimental.macros
+import chisel3.internal.sourceinfo._
+
+/**
+* BiConnect.connect executes a bidirectional connection element-wise.
+*
+* Note that the arguments are left and right (not source and sink) so the
+* intent is for the operation to be commutative.
+*
+* The connect operation will recurse down the left Data (with the right Data).
+* An exception will be thrown if a movement through the left cannot be matched
+* in the right (or if the right side has extra fields).
+*
+* See elemConnect for details on how the root connections are issued.
+*
+*/
+
+private[chisel3] object BiConnect {
+  // scalastyle:off method.name public.methods.have.type
+  // These are all the possible exceptions that can be thrown.
+  // These are from element-level connection
+  def BothDriversException =
+    BiConnectException(": Both Left and Right are drivers")
+  def NeitherDriverException =
+    BiConnectException(": Neither Left nor Right is a driver")
+  def UnknownDriverException =
+    BiConnectException(": Locally unclear whether Left or Right (both internal)")
+  def UnknownRelationException =
+    BiConnectException(": Left or Right unavailable to current module.")
+  // These are when recursing down aggregate types
+  def MismatchedVecException =
+    BiConnectException(": Left and Right are different length Vecs.")
+  def MissingLeftFieldException(field: String) =
+    BiConnectException(s".$field: Left Record missing field ($field).")
+  def MissingRightFieldException(field: String) =
+    BiConnectException(s": Right Record missing field ($field).")
+  def MismatchedException(left: String, right: String) =
+    BiConnectException(s": Left ($left) and Right ($right) have different types.")
+  def AttachAlreadyBulkConnectedException(sourceInfo: SourceInfo) =
+    BiConnectException(sourceInfo.makeMessage(": Analog previously bulk connected at " + _))
+  def DontCareCantBeSink =
+    BiConnectException(": DontCare cannot be a connection sink (LHS)")
+  // scalastyle:on method.name public.methods.have.type
+
+  /** This function is what recursively tries to connect a left and right together
+  *
+  * There is some cleverness in the use of internal try-catch to catch exceptions
+  * during the recursive decent and then rethrow them with extra information added.
+  * This gives the user a 'path' to where in the connections things went wrong.
+  */
+  def connect(sourceInfo: SourceInfo, connectCompileOptions: CompileOptions, left: Data, right: Data, context_mod: RawModule): Unit = { // scalastyle:ignore line.size.limit cyclomatic.complexity method.length
+    (left, right) match {
+      // Handle element case (root case)
+      case (left_a: Analog, right_a: Analog) =>
+        try {
+          analogAttach(sourceInfo, left_a, right_a, context_mod)
+        } catch {
+          // If attach fails, convert to BiConnectException
+          case attach.AttachException(message) => throw BiConnectException(message)
+        }
+      case (left_e: Element, right_e: Element) => {
+        elemConnect(sourceInfo, connectCompileOptions, left_e, right_e, context_mod)
+        // TODO(twigg): Verify the element-level classes are connectable
+      }
+      // Handle Vec case
+      case (left_v: Vec[Data@unchecked], right_v: Vec[Data@unchecked]) => {
+        if (left_v.length != right_v.length) {
+          throw MismatchedVecException
+        }
+        for (idx <- 0 until left_v.length) {
+          try {
+            implicit val compileOptions = connectCompileOptions
+            connect(sourceInfo, connectCompileOptions, left_v(idx), right_v(idx), context_mod)
+          } catch {
+            case BiConnectException(message) => throw BiConnectException(s"($idx)$message")
+          }
+        }
+      }
+      // Handle Vec connected to DontCare
+      case (left_v: Vec[Data@unchecked], DontCare) => {
+        for (idx <- 0 until left_v.length) {
+          try {
+            implicit val compileOptions = connectCompileOptions
+            connect(sourceInfo, connectCompileOptions, left_v(idx), right, context_mod)
+          } catch {
+            case BiConnectException(message) => throw BiConnectException(s"($idx)$message")
+          }
+        }
+      }
+      // Handle DontCare connected to Vec
+      case (DontCare, right_v: Vec[Data@unchecked]) => {
+        for (idx <- 0 until right_v.length) {
+          try {
+            implicit val compileOptions = connectCompileOptions
+            connect(sourceInfo, connectCompileOptions, left, right_v(idx), context_mod)
+          } catch {
+            case BiConnectException(message) => throw BiConnectException(s"($idx)$message")
+          }
+        }
+      }
+      // Handle Records defined in Chisel._ code (change to NotStrict)
+      case (left_r: Record, right_r: Record) => (left_r.compileOptions, right_r.compileOptions) match {
+        case (ExplicitCompileOptions.NotStrict, _) =>
+          left_r.bulkConnect(right_r)(sourceInfo, ExplicitCompileOptions.NotStrict)
+        case (_, ExplicitCompileOptions.NotStrict) =>
+          left_r.bulkConnect(right_r)(sourceInfo, ExplicitCompileOptions.NotStrict)
+        case _ => recordConnect(sourceInfo, connectCompileOptions, left_r, right_r, context_mod)
+      }
+
+      // Handle Records connected to DontCare (change to NotStrict)
+      case (left_r: Record, DontCare) =>
+        left_r.compileOptions match {
+          case ExplicitCompileOptions.NotStrict =>
+            left.bulkConnect(right)(sourceInfo, ExplicitCompileOptions.NotStrict)
+          case _ =>
+            // For each field in left, descend with right
+            for ((field, left_sub) <- left_r.elements) {
+              try {
+                connect(sourceInfo, connectCompileOptions, left_sub, right, context_mod)
+              } catch {
+                case BiConnectException(message) => throw BiConnectException(s".$field$message")
+              }
+            }
+        }
+      case (DontCare, right_r: Record) =>
+        right_r.compileOptions match {
+          case ExplicitCompileOptions.NotStrict =>
+            left.bulkConnect(right)(sourceInfo, ExplicitCompileOptions.NotStrict)
+          case _ =>
+            // For each field in left, descend with right
+            for ((field, right_sub) <- right_r.elements) {
+              try {
+                connect(sourceInfo, connectCompileOptions, left, right_sub, context_mod)
+              } catch {
+                case BiConnectException(message) => throw BiConnectException(s".$field$message")
+              }
+            }
+        }
+
+      // Left and right are different subtypes of Data so fail
+      case (left, right) => throw MismatchedException(left.toString, right.toString)
+    }
+  }
+
+  // Do connection of two Records
+  def recordConnect(sourceInfo: SourceInfo,
+                    connectCompileOptions: CompileOptions,
+                    left_r: Record,
+                    right_r: Record,
+                    context_mod: RawModule): Unit = {
+    // Verify right has no extra fields that left doesn't have
+    for((field, right_sub) <- right_r.elements) {
+      if(!left_r.elements.isDefinedAt(field)) {
+        if (connectCompileOptions.connectFieldsMustMatch) {
+          throw MissingLeftFieldException(field)
+        }
+      }
+    }
+    // For each field in left, descend with right
+    for((field, left_sub) <- left_r.elements) {
+      try {
+        right_r.elements.get(field) match {
+          case Some(right_sub) => connect(sourceInfo, connectCompileOptions, left_sub, right_sub, context_mod)
+          case None => {
+            if (connectCompileOptions.connectFieldsMustMatch) {
+              throw MissingRightFieldException(field)
+            }
+          }
+        }
+      } catch {
+        case BiConnectException(message) => throw BiConnectException(s".$field$message")
+      }
+    }
+  }
+
+
+  // These functions (finally) issue the connection operation
+  // Issue with right as sink, left as source
+  private def issueConnectL2R(left: Element, right: Element)(implicit sourceInfo: SourceInfo): Unit = {
+    // Source and sink are ambiguous in the case of a Bi/Bulk Connect (<>).
+    // If either is a DontCareBinding, just issue a DefInvalid for the other,
+    //  otherwise, issue a Connect.
+    (left.topBinding, right.topBinding) match {
+      case (lb: DontCareBinding, _) => pushCommand(DefInvalid(sourceInfo, right.lref))
+      case (_, rb: DontCareBinding) => pushCommand(DefInvalid(sourceInfo, left.lref))
+      case (_, _) => pushCommand(Connect(sourceInfo, right.lref, left.ref))
+    }
+  }
+  // Issue with left as sink, right as source
+  private def issueConnectR2L(left: Element, right: Element)(implicit sourceInfo: SourceInfo): Unit = {
+    // Source and sink are ambiguous in the case of a Bi/Bulk Connect (<>).
+    // If either is a DontCareBinding, just issue a DefInvalid for the other,
+    //  otherwise, issue a Connect.
+    (left.topBinding, right.topBinding) match {
+      case (lb: DontCareBinding, _) => pushCommand(DefInvalid(sourceInfo, right.lref))
+      case (_, rb: DontCareBinding) => pushCommand(DefInvalid(sourceInfo, left.lref))
+      case (_, _) => pushCommand(Connect(sourceInfo, left.lref, right.ref))
+    }
+  }
+
+  // This function checks if element-level connection operation allowed.
+  // Then it either issues it or throws the appropriate exception.
+  def elemConnect(implicit sourceInfo: SourceInfo, connectCompileOptions: CompileOptions, left: Element, right: Element, context_mod: RawModule): Unit = { // scalastyle:ignore line.size.limit cyclomatic.complexity method.length
+    import BindingDirection.{Internal, Input, Output} // Using extensively so import these
+    // If left or right have no location, assume in context module
+    // This can occur if one of them is a literal, unbound will error previously
+    val left_mod: BaseModule  = left.topBinding.location.getOrElse(context_mod)
+    val right_mod: BaseModule = right.topBinding.location.getOrElse(context_mod)
+
+    val left_direction = BindingDirection.from(left.topBinding, left.direction)
+    val right_direction = BindingDirection.from(right.topBinding, right.direction)
+
+    // CASE: Context is same module as left node and right node is in a child module
+    if( (left_mod == context_mod) &&
+        (right_mod._parent.map(_ == context_mod).getOrElse(false)) ) {
+      // Thus, right node better be a port node and thus have a direction hint
+      ((left_direction, right_direction): @unchecked) match {
+        //    CURRENT MOD   CHILD MOD
+        case (Input,        Input)  => issueConnectL2R(left, right)
+        case (Internal,     Input)  => issueConnectL2R(left, right)
+
+        case (Output,       Output) => issueConnectR2L(left, right)
+        case (Internal,     Output) => issueConnectR2L(left, right)
+
+        case (Input,        Output) => throw BothDriversException
+        case (Output,       Input)  => throw NeitherDriverException
+        case (_,            Internal) => throw UnknownRelationException
+      }
+    }
+
+    // CASE: Context is same module as right node and left node is in child module
+    else if( (right_mod == context_mod) &&
+             (left_mod._parent.map(_ == context_mod).getOrElse(false)) ) {
+      // Thus, left node better be a port node and thus have a direction hint
+      ((left_direction, right_direction): @unchecked) match {
+        //    CHILD MOD     CURRENT MOD
+        case (Input,        Input)  => issueConnectR2L(left, right)
+        case (Input,        Internal)         => issueConnectR2L(left, right)
+
+        case (Output,       Output) => issueConnectL2R(left, right)
+        case (Output,       Internal)         => issueConnectL2R(left, right)
+
+        case (Input,        Output) => throw NeitherDriverException
+        case (Output,       Input)  => throw BothDriversException
+        case (Internal,     _)      => throw UnknownRelationException
+      }
+    }
+
+    // CASE: Context is same module that both left node and right node are in
+    else if( (context_mod == left_mod) && (context_mod == right_mod) ) {
+      ((left_direction, right_direction): @unchecked) match {
+        //    CURRENT MOD   CURRENT MOD
+        case (Input,        Output) => issueConnectL2R(left, right)
+        case (Input,        Internal) => issueConnectL2R(left, right)
+        case (Internal,     Output) => issueConnectL2R(left, right)
+
+        case (Output,       Input)  => issueConnectR2L(left, right)
+        case (Output,       Internal) => issueConnectR2L(left, right)
+        case (Internal,     Input)  => issueConnectR2L(left, right)
+
+        case (Input,        Input)  => throw BothDriversException
+        case (Output,       Output) => throw BothDriversException
+        case (Internal,     Internal) => {
+          if (connectCompileOptions.dontAssumeDirectionality) {
+            throw UnknownDriverException
+          } else {
+            issueConnectR2L(left, right)
+          }
+        }
+      }
+    }
+
+    // CASE: Context is the parent module of both the module containing left node
+    //                                        and the module containing right node
+    //   Note: This includes case when left and right in same module but in parent
+    else if( (left_mod._parent.map(_ == context_mod).getOrElse(false)) &&
+             (right_mod._parent.map(_ == context_mod).getOrElse(false))
+    ) {
+      // Thus both nodes must be ports and have a direction hint
+      ((left_direction, right_direction): @unchecked) match {
+        //    CHILD MOD     CHILD MOD
+        case (Input,        Output) => issueConnectR2L(left, right)
+        case (Output,       Input)  => issueConnectL2R(left, right)
+
+        case (Input,        Input)  => throw NeitherDriverException
+        case (Output,       Output) => throw BothDriversException
+        case (_, Internal)          =>
+          if (connectCompileOptions.dontAssumeDirectionality) {
+            throw UnknownRelationException
+          } else {
+            issueConnectR2L(left, right)
+          }
+        case (Internal, _)          =>
+          if (connectCompileOptions.dontAssumeDirectionality) {
+            throw UnknownRelationException
+          } else {
+            issueConnectR2L(left, right)
+          }
+      }
+    }
+
+    // Not quite sure where left and right are compared to current module
+    // so just error out
+    else throw UnknownRelationException
+  }
+
+  // This function checks if analog element-level attaching is allowed
+  // Then it either issues it or throws the appropriate exception.
+  def analogAttach(implicit sourceInfo: SourceInfo, left: Analog, right: Analog, contextModule: RawModule): Unit = {
+    // Error if left or right is BICONNECTED in the current module already
+    for (elt <- left :: right :: Nil) {
+      elt.biConnectLocs.get(contextModule) match {
+        case Some(sl) => throw AttachAlreadyBulkConnectedException(sl)
+        case None => // Do nothing
+      }
+    }
+
+    // Do the attachment
+    attach.impl(Seq(left, right), contextModule)
+    // Mark bulk connected
+    left.biConnectLocs(contextModule) = sourceInfo
+    right.biConnectLocs(contextModule) = sourceInfo
+  }
+}
diff --git a/chiselFrontend/src/main/scala/chisel3/internal/Binding.scala b/chiselFrontend/src/main/scala/chisel3/internal/Binding.scala
new file mode 100644
index 00000000..34de36a3
--- /dev/null
+++ b/chiselFrontend/src/main/scala/chisel3/internal/Binding.scala
@@ -0,0 +1,106 @@
+// See LICENSE for license details.
+
+package chisel3.internal
+
+import chisel3._
+import chisel3.experimental.{BaseModule, RawModule}
+import chisel3.internal.firrtl.LitArg
+
+/** Requires that a node is hardware ("bound")
+  */
+object requireIsHardware {
+  def apply(node: Data, msg: String = ""): Unit = {
+    node._parent match {  // Compatibility layer hack
+      case Some(x: BaseModule) => x._compatAutoWrapPorts
+      case _ =>
+    }
+    if (!node.isSynthesizable) {
+      val prefix = if (msg.nonEmpty) s"$msg " else ""
+      throw ExpectedHardwareException(s"$prefix'$node' must be hardware, " +
+        "not a bare Chisel type. Perhaps you forgot to wrap it in Wire(_) or IO(_)?")
+    }
+  }
+}
+
+/** Requires that a node is a chisel type (not hardware, "unbound")
+  */
+object requireIsChiselType {
+  def apply(node: Data, msg: String = ""): Unit = if (node.isSynthesizable) {
+    val prefix = if (msg.nonEmpty) s"$msg " else ""
+    throw ExpectedChiselTypeException(s"$prefix'$node' must be a Chisel type, not hardware")
+  }
+}
+
+// Element only direction used for the Binding system only.
+private[chisel3] sealed abstract class BindingDirection
+private[chisel3] object BindingDirection {
+  /** Internal type or wire
+    */
+  case object Internal extends BindingDirection
+  /** Module port with output direction
+    */
+  case object Output extends BindingDirection
+  /** Module port with input direction
+    */
+  case object Input extends BindingDirection
+
+  /** Determine the BindingDirection of an Element given its top binding and resolved direction.
+    */
+  def from(binding: TopBinding, direction: ActualDirection): BindingDirection = {
+    binding match {
+      case PortBinding(_) => direction match {
+        case ActualDirection.Output => Output
+        case ActualDirection.Input => Input
+        case dir => throw new RuntimeException(s"Unexpected port element direction '$dir'")
+      }
+      case _ => Internal
+    }
+  }
+}
+
+// Location refers to 'where' in the Module hierarchy this lives
+sealed trait Binding {
+  def location: Option[BaseModule]
+}
+// Top-level binding representing hardware, not a pointer to another binding (like ChildBinding)
+sealed trait TopBinding extends Binding
+
+// Constrained-ness refers to whether 'bound by Module boundaries'
+// An unconstrained binding, like a literal, can be read by everyone
+sealed trait UnconstrainedBinding extends TopBinding {
+  def location: Option[BaseModule] = None
+}
+// A constrained binding can only be read/written by specific modules
+// Location will track where this Module is, and the bound object can be referenced in FIRRTL
+sealed trait ConstrainedBinding extends TopBinding {
+  def enclosure: BaseModule
+  def location: Option[BaseModule] = Some(enclosure)
+}
+
+// A binding representing a data that cannot be (re)assigned to.
+sealed trait ReadOnlyBinding extends TopBinding
+
+// TODO(twigg): Ops between unenclosed nodes can also be unenclosed
+// However, Chisel currently binds all op results to a module
+case class OpBinding(enclosure: RawModule) extends ConstrainedBinding with ReadOnlyBinding
+case class MemoryPortBinding(enclosure: RawModule) extends ConstrainedBinding
+case class PortBinding(enclosure: BaseModule) extends ConstrainedBinding
+case class RegBinding(enclosure: RawModule) extends ConstrainedBinding
+case class WireBinding(enclosure: RawModule) extends ConstrainedBinding
+
+case class ChildBinding(parent: Data) extends Binding {
+  def location: Option[BaseModule] = parent.topBinding.location
+}
+/** Special binding for Vec.sample_element */
+case class SampleElementBinding[T <: Data](parent: Vec[T]) extends Binding {
+  def location = parent.topBinding.location
+}
+// A DontCare element has a specific Binding, somewhat like a literal.
+// It is a source (RHS). It may only be connected/applied to sinks.
+case class DontCareBinding() extends UnconstrainedBinding
+
+sealed trait LitBinding extends UnconstrainedBinding with ReadOnlyBinding
+// Literal binding attached to a element that is not part of a Bundle.
+case class ElementLitBinding(litArg: LitArg) extends LitBinding
+// Literal binding attached to the root of a Bundle, containing literal values of its children.
+case class BundleLitBinding(litMap: Map[Data, LitArg]) extends LitBinding
diff --git a/chiselFrontend/src/main/scala/chisel3/internal/Builder.scala b/chiselFrontend/src/main/scala/chisel3/internal/Builder.scala
index d825f39d..664813f7 100644
--- a/chiselFrontend/src/main/scala/chisel3/internal/Builder.scala
+++ b/chiselFrontend/src/main/scala/chisel3/internal/Builder.scala
@@ -3,10 +3,11 @@
 package chisel3.internal
 
 import scala.util.DynamicVariable
-import scala.collection.mutable.{ArrayBuffer, HashMap}
+import scala.collection.mutable.ArrayBuffer
 import chisel3._
-import core._
-import firrtl._
+import chisel3.experimental._
+import chisel3.internal.firrtl._
+import chisel3.internal.naming._
 import _root_.firrtl.annotations.{CircuitName, ComponentName, ModuleName, Named}
 
 private[chisel3] class Namespace(keywords: Set[String]) {
@@ -186,7 +187,7 @@ private[chisel3] class DynamicContext() {
   var currentClock: Option[Clock] = None
   var currentReset: Option[Reset] = None
   val errors = new ErrorLog
-  val namingStack = new internal.naming.NamingStack
+  val namingStack = new NamingStack
 }
 
 //scalastyle:off number.of.methods
@@ -204,7 +205,7 @@ private[chisel3] object Builder {
   private def initializeSingletons(): Unit = {
     // This used to contain:
     //    val dummy = core.DontCare
-    //  but this would occasionally produce hangs dues to static initialization deadlock
+    //  but this would occasionally produce hangs due to static initialization deadlock
     //  when Builder initialization collided with chisel3.package initialization of the DontCare value.
     // See:
     //  http://ternarysearch.blogspot.com/2013/07/static-initialization-deadlock.html
@@ -212,14 +213,14 @@ private[chisel3] object Builder {
     //  https://stackoverflow.com/questions/28631656/runnable-thread-state-but-in-object-wait
   }
 
-  def namingStackOption: Option[internal.naming.NamingStack] = dynamicContextVar.value.map(_.namingStack)
+  def namingStackOption: Option[NamingStack] = dynamicContextVar.value.map(_.namingStack)
 
   def idGen: IdGen = chiselContext.value.idGen
 
   def globalNamespace: Namespace = dynamicContext.globalNamespace
   def components: ArrayBuffer[Component] = dynamicContext.components
   def annotations: ArrayBuffer[ChiselAnnotation] = dynamicContext.annotations
-  def namingStack: internal.naming.NamingStack = dynamicContext.namingStack
+  def namingStack: NamingStack = dynamicContext.namingStack
 
   def currentModule: Option[BaseModule] = dynamicContextVar.value match {
     case Some(dyanmicContext) => dynamicContext.currentModule
@@ -366,19 +367,19 @@ private[chisel3] object Builder {
   * objects.
   */
 object DynamicNamingStack {
-  def pushContext(): internal.naming.NamingContextInterface = {
+  def pushContext(): NamingContextInterface = {
     Builder.namingStackOption match {
       case Some(namingStack) => namingStack.pushContext()
-      case None => internal.naming.DummyNamer
+      case None => DummyNamer
     }
   }
 
-  def popReturnContext[T <: Any](prefixRef: T, until: internal.naming.NamingContextInterface): T = {
+  def popReturnContext[T <: Any](prefixRef: T, until: NamingContextInterface): T = {
     until match {
-      case internal.naming.DummyNamer =>
+      case DummyNamer =>
         require(Builder.namingStackOption.isEmpty,
           "Builder context must remain stable throughout a chiselName-annotated function invocation")
-      case context: internal.naming.NamingContext =>
+      case context: NamingContext =>
         require(Builder.namingStackOption.isDefined,
           "Builder context must remain stable throughout a chiselName-annotated function invocation")
         Builder.namingStackOption.get.popContext(prefixRef, context)
diff --git a/chiselFrontend/src/main/scala/chisel3/internal/Error.scala b/chiselFrontend/src/main/scala/chisel3/internal/Error.scala
index 59f32542..91d9d7de 100644
--- a/chiselFrontend/src/main/scala/chisel3/internal/Error.scala
+++ b/chiselFrontend/src/main/scala/chisel3/internal/Error.scala
@@ -4,8 +4,6 @@ package chisel3.internal
 
 import scala.collection.mutable.{ArrayBuffer, LinkedHashMap}
 
-import chisel3.core._
-
 class ChiselException(message: String, cause: Throwable = null) extends Exception(message, cause) {
 
   val blacklistPackages = Set("chisel3", "scala", "java", "sun", "sbt")
@@ -126,7 +124,7 @@ private[chisel3] class ErrorLog {
           "java.",
           "scala.",
           "chisel3.internal.",
-          "chisel3.core.",
+          "chisel3.experimental.",
           "chisel3.package$"  // for some compatibility / deprecated types
           )
       !chiselPrefixes.filter(className.startsWith(_)).isEmpty
diff --git a/chiselFrontend/src/main/scala/chisel3/internal/MonoConnect.scala b/chiselFrontend/src/main/scala/chisel3/internal/MonoConnect.scala
new file mode 100644
index 00000000..91f1bfd8
--- /dev/null
+++ b/chiselFrontend/src/main/scala/chisel3/internal/MonoConnect.scala
@@ -0,0 +1,246 @@
+// See LICENSE for license details.
+
+package chisel3.internal
+
+import chisel3._
+import chisel3.experimental.{BaseModule, EnumType, FixedPoint, RawModule, UnsafeEnum}
+import chisel3.internal.Builder.pushCommand
+import chisel3.internal.firrtl.{Connect, DefInvalid}
+import scala.language.experimental.macros
+import chisel3.internal.sourceinfo.SourceInfo
+
+/**
+* MonoConnect.connect executes a mono-directional connection element-wise.
+*
+* Note that this isn't commutative. There is an explicit source and sink
+* already determined before this function is called.
+*
+* The connect operation will recurse down the left Data (with the right Data).
+* An exception will be thrown if a movement through the left cannot be matched
+* in the right. The right side is allowed to have extra Record fields.
+* Vecs must still be exactly the same size.
+*
+* See elemConnect for details on how the root connections are issued.
+*
+* Note that a valid sink must be writable so, one of these must hold:
+* - Is an internal writable node (Reg or Wire)
+* - Is an output of the current module
+* - Is an input of a submodule of the current module
+*
+* Note that a valid source must be readable so, one of these must hold:
+* - Is an internal readable node (Reg, Wire, Op)
+* - Is a literal
+* - Is a port of the current module or submodule of the current module
+*/
+
+private[chisel3] object MonoConnect {
+  // scalastyle:off method.name public.methods.have.type
+  // These are all the possible exceptions that can be thrown.
+  // These are from element-level connection
+  def UnreadableSourceException =
+    MonoConnectException(": Source is unreadable from current module.")
+  def UnwritableSinkException =
+    MonoConnectException(": Sink is unwriteable by current module.")
+  def UnknownRelationException =
+    MonoConnectException(": Sink or source unavailable to current module.")
+  // These are when recursing down aggregate types
+  def MismatchedVecException =
+    MonoConnectException(": Sink and Source are different length Vecs.")
+  def MissingFieldException(field: String) =
+    MonoConnectException(s": Source Record missing field ($field).")
+  def MismatchedException(sink: String, source: String) =
+    MonoConnectException(s": Sink ($sink) and Source ($source) have different types.")
+  def DontCareCantBeSink =
+    MonoConnectException(": DontCare cannot be a connection sink (LHS)")
+  // scalastyle:on method.name public.methods.have.type
+
+  /** This function is what recursively tries to connect a sink and source together
+  *
+  * There is some cleverness in the use of internal try-catch to catch exceptions
+  * during the recursive decent and then rethrow them with extra information added.
+  * This gives the user a 'path' to where in the connections things went wrong.
+  */
+  def connect(  //scalastyle:off cyclomatic.complexity method.length
+      sourceInfo: SourceInfo,
+      connectCompileOptions: CompileOptions,
+      sink: Data,
+      source: Data,
+      context_mod: RawModule): Unit =
+    (sink, source) match {
+
+      // Handle legal element cases, note (Bool, Bool) is caught by the first two, as Bool is a UInt
+      case (sink_e: Bool, source_e: UInt) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+      case (sink_e: UInt, source_e: Bool) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+      case (sink_e: UInt, source_e: UInt) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+      case (sink_e: SInt, source_e: SInt) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+      case (sink_e: FixedPoint, source_e: FixedPoint) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+      case (sink_e: Clock, source_e: Clock) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+      case (sink_e: EnumType, source_e: UnsafeEnum) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+      case (sink_e: EnumType, source_e: EnumType) if sink_e.typeEquivalent(source_e) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+      case (sink_e: UnsafeEnum, source_e: UInt) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+
+      // Handle Vec case
+      case (sink_v: Vec[Data @unchecked], source_v: Vec[Data @unchecked]) =>
+        if(sink_v.length != source_v.length) { throw MismatchedVecException }
+        for(idx <- 0 until sink_v.length) {
+          try {
+            implicit val compileOptions = connectCompileOptions
+            connect(sourceInfo, connectCompileOptions, sink_v(idx), source_v(idx), context_mod)
+          } catch {
+            case MonoConnectException(message) => throw MonoConnectException(s"($idx)$message")
+          }
+        }
+      // Handle Vec connected to DontCare. Apply the DontCare to individual elements.
+      case (sink_v: Vec[Data @unchecked], DontCare) =>
+        for(idx <- 0 until sink_v.length) {
+          try {
+            implicit val compileOptions = connectCompileOptions
+            connect(sourceInfo, connectCompileOptions, sink_v(idx), source, context_mod)
+          } catch {
+            case MonoConnectException(message) => throw MonoConnectException(s"($idx)$message")
+          }
+        }
+
+      // Handle Record case
+      case (sink_r: Record, source_r: Record) =>
+        // For each field, descend with right
+        for((field, sink_sub) <- sink_r.elements) {
+          try {
+            source_r.elements.get(field) match {
+              case Some(source_sub) => connect(sourceInfo, connectCompileOptions, sink_sub, source_sub, context_mod)
+              case None => {
+                if (connectCompileOptions.connectFieldsMustMatch) {
+                  throw MissingFieldException(field)
+                }
+              }
+            }
+          } catch {
+            case MonoConnectException(message) => throw MonoConnectException(s".$field$message")
+          }
+        }
+      // Handle Record connected to DontCare. Apply the DontCare to individual elements.
+      case (sink_r: Record, DontCare) =>
+        // For each field, descend with right
+        for((field, sink_sub) <- sink_r.elements) {
+          try {
+            connect(sourceInfo, connectCompileOptions, sink_sub, source, context_mod)
+          } catch {
+            case MonoConnectException(message) => throw MonoConnectException(s".$field$message")
+          }
+        }
+
+      // Source is DontCare - it may be connected to anything. It generates a defInvalid for the sink.
+      case (sink, DontCare) => pushCommand(DefInvalid(sourceInfo, sink.lref))
+      // DontCare as a sink is illegal.
+      case (DontCare, _) => throw DontCareCantBeSink
+      // Sink and source are different subtypes of data so fail
+      case (sink, source) => throw MismatchedException(sink.toString, source.toString)
+    }
+
+  // This function (finally) issues the connection operation
+  private def issueConnect(sink: Element, source: Element)(implicit sourceInfo: SourceInfo): Unit = {
+    // If the source is a DontCare, generate a DefInvalid for the sink,
+    //  otherwise, issue a Connect.
+    source.topBinding match {
+      case b: DontCareBinding => pushCommand(DefInvalid(sourceInfo, sink.lref))
+      case _ => pushCommand(Connect(sourceInfo, sink.lref, source.ref))
+    }
+  }
+
+  // This function checks if element-level connection operation allowed.
+  // Then it either issues it or throws the appropriate exception.
+  def elemConnect(implicit sourceInfo: SourceInfo, connectCompileOptions: CompileOptions, sink: Element, source: Element, context_mod: RawModule): Unit = { // scalastyle:ignore line.size.limit
+    import BindingDirection.{Internal, Input, Output} // Using extensively so import these
+    // If source has no location, assume in context module
+    // This can occur if is a literal, unbound will error previously
+    val sink_mod: BaseModule   = sink.topBinding.location.getOrElse(throw UnwritableSinkException)
+    val source_mod: BaseModule = source.topBinding.location.getOrElse(context_mod)
+
+    val sink_direction = BindingDirection.from(sink.topBinding, sink.direction)
+    val source_direction = BindingDirection.from(source.topBinding, source.direction)
+
+    // CASE: Context is same module that both left node and right node are in
+    if( (context_mod == sink_mod) && (context_mod == source_mod) ) {
+      ((sink_direction, source_direction): @unchecked) match {
+        //    SINK          SOURCE
+        //    CURRENT MOD   CURRENT MOD
+        case (Output,       _) => issueConnect(sink, source)
+        case (Internal,     _) => issueConnect(sink, source)
+        case (Input,        _) => throw UnwritableSinkException
+      }
+    }
+
+    // CASE: Context is same module as sink node and right node is in a child module
+    else if( (sink_mod == context_mod) &&
+             (source_mod._parent.map(_ == context_mod).getOrElse(false)) ) {
+      // Thus, right node better be a port node and thus have a direction
+      ((sink_direction, source_direction): @unchecked) match {
+        //    SINK          SOURCE
+        //    CURRENT MOD   CHILD MOD
+        case (Internal,     Output) => issueConnect(sink, source)
+        case (Internal,     Input)  => issueConnect(sink, source)
+        case (Output,       Output) => issueConnect(sink, source)
+        case (Output,       Input)  => issueConnect(sink, source)
+        case (_,            Internal) => {
+          if (!(connectCompileOptions.dontAssumeDirectionality)) {
+            issueConnect(sink, source)
+          } else {
+            throw UnreadableSourceException
+          }
+        }
+        case (Input,        Output) if (!(connectCompileOptions.dontTryConnectionsSwapped)) => issueConnect(source, sink) // scalastyle:ignore line.size.limit
+        case (Input,        _)    => throw UnwritableSinkException
+      }
+    }
+
+    // CASE: Context is same module as source node and sink node is in child module
+    else if( (source_mod == context_mod) &&
+             (sink_mod._parent.map(_ == context_mod).getOrElse(false)) ) {
+      // Thus, left node better be a port node and thus have a direction
+      ((sink_direction, source_direction): @unchecked) match {
+        //    SINK          SOURCE
+        //    CHILD MOD     CURRENT MOD
+        case (Input,        _) => issueConnect(sink, source)
+        case (Output,       _) => throw UnwritableSinkException
+        case (Internal,     _) => throw UnwritableSinkException
+      }
+    }
+
+    // CASE: Context is the parent module of both the module containing sink node
+    //                                        and the module containing source node
+    //   Note: This includes case when sink and source in same module but in parent
+    else if( (sink_mod._parent.map(_ == context_mod).getOrElse(false)) &&
+             (source_mod._parent.map(_ == context_mod).getOrElse(false))
+    ) {
+      // Thus both nodes must be ports and have a direction
+      ((sink_direction, source_direction): @unchecked) match {
+        //    SINK          SOURCE
+        //    CHILD MOD     CHILD MOD
+        case (Input,        Input)  => issueConnect(sink, source)
+        case (Input,        Output) => issueConnect(sink, source)
+        case (Output,       _)      => throw UnwritableSinkException
+        case (_,            Internal) => {
+          if (!(connectCompileOptions.dontAssumeDirectionality)) {
+            issueConnect(sink, source)
+          } else {
+            throw UnreadableSourceException
+          }
+        }
+        case (Internal,     _)      => throw UnwritableSinkException
+      }
+    }
+
+    // Not quite sure where left and right are compared to current module
+    // so just error out
+    else throw UnknownRelationException
+  }
+}
diff --git a/chiselFrontend/src/main/scala/chisel3/internal/firrtl/IR.scala b/chiselFrontend/src/main/scala/chisel3/internal/firrtl/IR.scala
index 7854efdb..2cb4d092 100644
--- a/chiselFrontend/src/main/scala/chisel3/internal/firrtl/IR.scala
+++ b/chiselFrontend/src/main/scala/chisel3/internal/firrtl/IR.scala
@@ -3,9 +3,9 @@
 package chisel3.internal.firrtl
 
 import chisel3._
-import core._
 import chisel3.internal._
-import chisel3.internal.sourceinfo.{SourceInfo, NoSourceInfo}
+import chisel3.internal.sourceinfo.SourceInfo
+import chisel3.experimental.{BaseModule, ChiselAnnotation, Param, RawModule}
 
 // scalastyle:off number.of.types