Use some enums in compiler

Author: odersky

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -39,13 +39,9 @@ object desugar {
    */
   val CheckIrrefutable: Property.Key[MatchCheck] = new Property.StickyKey
 
-  /** What static check should be applied to a Match (none, irrefutable, exhaustive) */
-  class MatchCheck(val n: Int) extends AnyVal
-  object MatchCheck {
-    val None = new MatchCheck(0)
-    val Exhaustive = new MatchCheck(1)
-    val IrrefutablePatDef = new MatchCheck(2)
-    val IrrefutableGenFrom = new MatchCheck(3)
+  /** What static check should be applied to a Match? */
+  enum MatchCheck {
+    case None, Exhaustive, IrrefutablePatDef, IrrefutableGenFrom
   }
 
   /** Info of a variable in a pattern: The named tree and its type */

compiler/src/dotty/tools/dotc/ast/untpd.scala

@@ -123,12 +123,11 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   class XMLBlock(stats: List[Tree], expr: Tree)(implicit @constructorOnly src: SourceFile) extends Block(stats, expr)
 
   /** An enum to control checking or filtering of patterns in GenFrom trees */
-  class GenCheckMode(val x: Int) extends AnyVal
-  object GenCheckMode {
-    val Ignore = new GenCheckMode(0)  // neither filter nor check since filtering was done before
-    val Check = new GenCheckMode(1)   // check that pattern is irrefutable
-    val FilterNow = new GenCheckMode(2)  // filter out non-matching elements since we are not in -strict
-    val FilterAlways = new GenCheckMode(3) // filter out non-matching elements since pattern is prefixed by `case`
+  enum GenCheckMode {
+    case Ignore       // neither filter nor check since filtering was done before
+    case Check        // check that pattern is irrefutable
+    case FilterNow    //filter out non-matching elements since we are not in -strict
+    case FilterAlways // filter out non-matching elements since pattern is prefixed by `case`
   }
 
   // ----- Modifiers -----------------------------------------------------