Add PartialDataView.supertype (backport #2826) (#2827)

* Add PartialDataView.supertype (#2826)

This factory method makes it easy to create PartialDataViews from a
Bundle type to its supertype. Because of the typing relationship, there
is no need to provide a mapping between fields. The only thing necessary
is to provide a function for constructing an instance of the supertype
from an instance of the subtype.

(cherry picked from commit 251d454a224e5a961438ba0ea41134d7da7a5992)

# Conflicts:
#	core/src/main/scala/chisel3/experimental/dataview/package.scala
#	src/test/scala/chiselTests/experimental/DataView.scala

* Resolve backport conflicts

Co-authored-by: Jack Koenig <koenig@sifive.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/src/test/scala/chiselTests/experimental/DataView.scala b/src/test/scala/chiselTests/experimental/DataView.scala
index ac8357f0..3673778b 100644
--- a/src/test/scala/chiselTests/experimental/DataView.scala
+++ b/src/test/scala/chiselTests/experimental/DataView.scala
@@ -177,6 +177,28 @@ class DataViewSpec extends ChiselFlatSpec {
     chirrtl should include("fooOut.foo <= barIn.foo")
   }
 
+  it should "be easy to make a PartialDataView viewing a Bundle as a Parent Bundle type" in {
+    class Foo(x: Int) extends Bundle {
+      val foo = UInt(x.W)
+    }
+    class Bar(val x: Int) extends Foo(x) {
+      val bar = UInt(x.W)
+    }
+    implicit val view = PartialDataView.supertype[Bar, Foo](b => new Foo(b.x))
+    class MyModule extends Module {
+      val fooIn = IO(Input(new Foo(8)))
+      val barOut = IO(Output(new Bar(8)))
+      barOut.viewAs[Foo] := fooIn
+
+      val barIn = IO(Input(new Bar(8)))
+      val fooOut = IO(Output(new Foo(8)))
+      fooOut := barIn.viewAs[Foo]
+    }
+    val chirrtl = ChiselStage.emitChirrtl(new MyModule)
+    chirrtl should include("barOut.foo <= fooIn.foo")
+    chirrtl should include("fooOut.foo <= barIn.foo")
+  }
+
   it should "error if viewing a parent Bundle as a child Bundle type" in {
     assertTypeError("""
       class Foo extends Bundle {