Introduce VecLiterals (#1834)

This PR provides for support for Vec literals. They can be one of two forms
Inferred:
```
Vec.Lit(0x1.U, 0x2.U)
```
or explicit:
```
Vec(2, UInt(4.W)).Lit(0 -> 0x1.U, 1 -> 0x2.U)
```
- Explicit form allows for partial, or sparse, literals.
- Vec literals can be used as Register initializers
- Arbitrary nesting (consistent with type constraints is allowed)

1 files changed, 4 insertions, 0 deletions

diff --git a/core/src/main/scala/chisel3/Element.scala b/core/src/main/scala/chisel3/Element.scala
index 0c99ff70..40291b12 100644
--- a/core/src/main/scala/chisel3/Element.scala
+++ b/core/src/main/scala/chisel3/Element.scala
@@ -30,6 +30,10 @@ abstract class Element extends Data {
       case Some(litArg) => Some(ElementLitBinding(litArg))
       case _ => Some(DontCareBinding())
     }
+    case Some(VecLitBinding(litMap)) => litMap.get(this) match {
+      case Some(litArg) => Some(ElementLitBinding(litArg))
+      case _ => Some(DontCareBinding())
+    }
     case topBindingOpt => topBindingOpt
   }