Deprecate old Reg with nulls constructor (#455)

1 files changed, 39 insertions, 1 deletions

diff --git a/src/main/scala/chisel3/package.scala b/src/main/scala/chisel3/package.scala
index 0ccdfc29..191b636e 100644
--- a/src/main/scala/chisel3/package.scala
+++ b/src/main/scala/chisel3/package.scala
@@ -155,7 +155,45 @@ package object chisel3 {    // scalastyle:ignore package.object.name
 
   val printf = chisel3.core.printf
 
-  val Reg = chisel3.core.Reg
+  val RegNext = chisel3.core.RegNext
+  val RegInit = chisel3.core.RegInit
+  object Reg {
+    import chisel3.core.{Binding, CompileOptions}
+    import chisel3.internal.sourceinfo.SourceInfo
+    import chisel3.internal.throwException
+
+    // Passthrough for chisel3.core.Reg
+    // TODO: make val Reg = chisel3.core.Reg once we eliminate the legacy Reg constructor
+    def apply[T <: Data](t: T)(implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): T =
+      chisel3.core.Reg(t)
+
+    @deprecated("Use Reg(t), RegNext(next, [init]) or RegInit([t], init) instead", "chisel3")
+    def apply[T <: Data](t: T = null, next: T = null, init: T = null)
+        (implicit sourceInfo: SourceInfo, compileOptions: CompileOptions): T = {
+      if (t ne null) {
+        val reg = if (init ne null) {
+          RegInit(t, init)
+        } else {
+          chisel3.core.Reg(t)
+        }
+        if (next ne null) {
+          Binding.checkSynthesizable(next, s"'next' ($next)")  // TODO: move into connect?
+          reg := next
+        }
+        reg
+      } else if (next ne null) {
+        if (init ne null) {
+          RegNext(next, init)
+        } else {
+          RegNext(next)
+        }
+      } else if (init ne null) {
+        RegInit(init)
+      } else {
+        throwException("cannot infer type")
+      }
+    }
+  }
 
   val when = chisel3.core.when
   type WhenContext = chisel3.core.WhenContext