Add DataView (#1955)

DataView is a mechanism for "viewing" Scala objects as a subtype of
`Data`. Often, this is useful for viewing one subtype of `Data`, as
another. One can think about a DataView as a cross between a
customizable cast and an untagged union.

A DataView has a Target type `T`, and a View type `V`. DataView requires
that an implementation of `DataProduct` is available for Target types.
DataProduct is a type class that provides a way to iterate on `Data`
children of objects of implementing types.

If a DataView is provided for a type T to a type V, then the function
.viewAs[V] (of type T => V) is available. The object (of type T) returned
by .viewAs is called a "View" and can be used as both an rvalue and an
lvalue. Unlike when using an .asTypeOf cast, connecting to a "View" will
connect to the associated field or fields of the underlying Target.

DataView also enables .viewAsSupertype which is available for viewing
Bundles as a parent Bundle type. It is similar to .viewAs but requires
a prototype object of the Target type which will be cloned in order to
create the returned View. .viewAsSupertype maps between the
corresponding fields of the parent and child Bundle types.

1 files changed, 2 insertions, 2 deletions

diff --git a/core/src/main/scala/chisel3/ModuleAspect.scala b/core/src/main/scala/chisel3/ModuleAspect.scala
index 4e37ab35..a528fa72 100644
--- a/core/src/main/scala/chisel3/ModuleAspect.scala
+++ b/core/src/main/scala/chisel3/ModuleAspect.scala
@@ -2,7 +2,7 @@
 
 package chisel3
 
-import chisel3.internal.Builder
+import chisel3.internal.{Builder, PseudoModule}
 
 /** Used by Chisel Aspects to inject Chisel code into modules, after they have been elaborated.
   * This is an internal API - don't use!
@@ -13,7 +13,7 @@ import chisel3.internal.Builder
   * @param moduleCompileOptions
   */
 abstract class ModuleAspect private[chisel3] (module: RawModule)
-                                             (implicit moduleCompileOptions: CompileOptions) extends RawModule {
+                                             (implicit moduleCompileOptions: CompileOptions) extends RawModule with PseudoModule {
 
   Builder.addAspect(module, this)