Fix a bug in FlattenSpec where ChiselStage was running the FIRRTL
compiler in ChiselStage and then re-running the FIRRTL compiler. This
changes it to be like InlineSpec and to not run FIRRTL during
ChiselStage.

This was manually backported to 3.3.x.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Remove Deprecated Usages of chisel3.Driver, CircuitForm

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Co-authored-by: Chick Markley <chick@qrhino.com>
Co-authored-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>
Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

This migrates the tests to Chisel 3.4/FIRRTL 1.4. This primarily
involves removing usages of deprecated methods including:

- Remove usages of Driver
- Use ChiselStage methods instead of BackendCompilationUtilities
  methods
- Use Dependency API for custom transforms
- Use extractCause to unpack StackError

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Adds a new method, chiselTests.Util.containsCause, that will search
for a polymorphic exception anywhere in a stack trace. This is useful
if exceptions may move around (e.g., if they are suddenly wrapped in a
StageError).

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Co-authored-by: Albert Magyar <albert.magyar@gmail.com>

* Canonicalize construction of empty Decoupled

* Change signature after dev meeting discussion
* Make EmptyBundle private and final

* Add test case for Decoupled with no payload

* Apply suggestions from code review

Co-authored-by: Richard Lin <richard.lin@berkeley.edu>

Co-authored-by: Albert Magyar <albert.magyar@gmail.com>
Co-authored-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>
Co-authored-by: Adam Izraelevitz <azidar@gmail.com>
Co-authored-by: Richard Lin <richard.lin@berkeley.edu>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

* Closes #1385

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Move LFSR16 to Compatibility Mode (Deprecated in 3.2)

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Co-authored-by: Chick Markley <chick@qrhino.com>

* Immediately throw Builder.error errors outside hardware context

* Add example of hidden no-hardware-context error from #1422

Co-authored-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

* Added group chisel API

* Removed println

* Added scaladoc

* Added more tests

* Cleaned spacing and removed println

Co-authored-by: Chick Markley <chick@qrhino.com>
Co-authored-by: Jim Lawson <ucbjrl@berkeley.edu>
Co-authored-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Co-authored-by: Scala Steward <me@scala-steward.org>
Co-authored-by: Scala Steward <43047562+scala-steward@users.noreply.github.com>

Co-authored-by: Jim Lawson <ucbjrl@berkeley.edu>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

* Update scalacheck-1-14 to 3.1.1.1

* Update scalacheck-1-14 to 3.1.1.1

Co-authored-by: Jim Lawson <ucbjrl@berkeley.edu>

Co-authored-by: Jim Lawson <ucbjrl@berkeley.edu>

Fix Double Elaboration Backportably

Remove the requirement that FirrtlStage runs elaboration (this should
be implicit) and remove the unneeded invalidation of elaboration by
the Emitter. Due to Convert currently NOT invalidating Elaborate (when
it should), add an optionalPrerequisiteOf to ensure that the Emitter
runs before the Convert phase.

Co-authored-by: David Biancolin <david.biancolin@gmail.com>
Co-authored-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>
Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

* Update scalatest to 3.1.1

* Update scalatest to 3.1.1

* Update scalatest to 3.1.1

* Add missing org.scalatest.flatspec.AnyFlatSpec import.

Co-authored-by: Scala Steward <me@scala-steward.org>
Co-authored-by: Scala Steward <43047562+scala-steward@users.noreply.github.com>

This replaces the rules for 3.2.x

Co-authored-by: Adam Izraelevitz <azidar@gmail.com>

This reverts commit c279860c.

Co-authored-by: Scala Steward <me@scala-steward.org>

Remove var from object Counter.apply, using a Wire instead. Also improve
some ScalaDoc and the class Counter require message.