Simplify Enum API (#385)

Get rid of some cruft exposed in #373

This also allows Bits.fromtInt(...) to be removed. Yay!

All old APIs (with some new restrictions, rocket still works fine) are preserved without deprecation in Chisel._, aside from the non-compile-time-checkable Map[] enum constructor which probably should have been deprecated during chisel2. The Map[] enums have been removed from chisel3._ without deprecation.

The new restriction is that nodeType (legacy API) may only be of UInt type with unspecified width. Note that Bits() creates a UInt, and if you can't control the enum values, it makes little sense to specify a bitwidth.

1 files changed, 14 insertions, 27 deletions

diff --git a/src/main/scala/chisel3/util/Enum.scala b/src/main/scala/chisel3/util/Enum.scala
index 55b595ee..45aee62a 100644
--- a/src/main/scala/chisel3/util/Enum.scala
+++ b/src/main/scala/chisel3/util/Enum.scala
@@ -7,15 +7,15 @@ package chisel3.util
 
 import chisel3._
 
-object Enum {
+trait Enum {
   /** Returns a sequence of Bits subtypes with values from 0 until n. Helper method. */
-  private def createValues[T <: Bits](nodeType: T, n: Int): Seq[T] =
-    (0 until n).map(x => nodeType.fromInt(x, log2Up(n)))
+  protected def createValues(n: Int): Seq[UInt] =
+    (0 until n).map(_.U(log2Up(n).W))
 
-  /** Returns n unique values of the specified type. Can be used with unpacking to define enums.
+  /** Returns n unique UInt values, use with unpacking to specify an enumeration.
     *
     * @example {{{
-    * val state_on :: state_off :: Nil = Enum(UInt(), 2)
+    * val state_on :: state_off :: Nil = Enum(2)
     * val current_state = UInt()
     * switch (current_state) {
     *   is (state_on) {
@@ -26,28 +26,15 @@ object Enum {
     *   }
     * }
     * }}}
-    *
     */
-  def apply[T <: Bits](nodeType: T, n: Int): List[T] = createValues(nodeType, n).toList
-
-  /** Returns a map of the input symbols to unique values of the specified type.
-    *
-    * @example {{{
-    * val states = Enum(UInt(), 'on, 'off)
-    * val current_state = UInt()
-    * switch (current_state) {
-    *   is (states('on)) {
-    *     ...
-    *   }
-    *   if (states('off)) {
-    *     ..
-    *   }
-    * }
-    * }}}
-    */
-  def apply[T <: Bits](nodeType: T, l: Symbol *): Map[Symbol, T] = (l zip createValues(nodeType, l.length)).toMap
+  def apply(n: Int): List[UInt] = createValues(n).toList
+}
 
-  /** Returns a map of the input symbols to unique values of the specified type.
-    */
-  def apply[T <: Bits](nodeType: T, l: List[Symbol]): Map[Symbol, T] = (l zip createValues(nodeType, l.length)).toMap
+object Enum extends Enum {
+  @deprecated("use Enum(n)", "chisel3, will be removed soon")
+  def apply[T <: Bits](nodeType: T, n: Int): List[T] = {
+    require(nodeType.isInstanceOf[UInt], "Only UInt supported for enums")
+    require(!nodeType.widthKnown, "Bit width may no longer be specified for enums")
+    apply(n).asInstanceOf[List[T]]
+  }
 }