Fix chisel3 <> for Bundles that contain compatibility Bundles (Take 2) (

#2031)

PR #2023 fixed a composition issue for chisel3 biconnects delegating to
FIRRTL partial connect when compatibility mode Bundles are elements of
chisel3 Bundles. It missed an important case though that caused
previously working code to break.

The bug is fixed by doing the automatic flipping for compatibility mode
Bundles that have "Input" as a direction in addition to those that are
"Flipped".

core/src/main/scala/chisel3/internal/BiConnect.scala

@@ -120,9 +120,10 @@ private[chisel3] object BiConnect {
         if (notStrict) {
           // chisel3 <> is commutative but FIRRTL <- is not
           val flipped = {
+            import ActualDirection._
             // Everything is flipped when it's the port of a child
             val childPort = left_r._parent.get != context_mod
-            val isFlipped = left_r.direction == ActualDirection.Bidirectional(ActualDirection.Flipped)
+            val isFlipped = Seq(Bidirectional(Flipped), Input).contains(left_r.direction)
             isFlipped ^ childPort
           }
           val (newLeft, newRight) = if (flipped) pair.swap else pair

src/test/scala/chiselTests/CompatibilityInteroperabilitySpec.scala

@@ -294,16 +294,21 @@ class CompatibiltyInteroperabilitySpec extends ChiselFlatSpec {
     compile {
       object Compat {
         import Chisel._
-        class Foo extends Bundle {
+        class BiDir extends Bundle {
           val a = Input(UInt(8.W))
           val b = Output(UInt(8.W))
         }
+        class Struct extends Bundle {
+          val a = UInt(8.W)
+        }
       }
       import chisel3._
       import Compat._
       class Bar extends Bundle {
-        val foo1 = new Foo
-        val foo2 = Flipped(new Foo)
+        val bidir1 = new BiDir
+        val bidir2 = Flipped(new BiDir)
+        val struct1 = Output(new Struct)
+        val struct2 = Input(new Struct)
       }
       // Check every connection both ways to see that chisel3 <>'s commutativity holds
       class Child extends RawModule {