Refactor NameTags

 - drop tags that cannot be part of Tasty trees from TastyFormat
 - move them to a new object, NameTags.
 - add comments explaining what each name tag represents.

Author: odersky

compiler/src/dotty/tools/dotc/core/NameKinds.scala

@@ -6,7 +6,7 @@ import Names._
 import NameOps._
 import StdNames._
 import util.DotClass
-import tasty.TastyFormat._
+import NameTags._
 import Decorators._
 import Contexts.Context
 import collection.mutable

compiler/src/dotty/tools/dotc/core/NameTags.scala

@@ -0,0 +1,58 @@
+package dotty.tools
+package dotc
+package core
+
+import tasty.TastyFormat
+
+/** The possible tags of a NameKind */
+object NameTags extends TastyFormat.NameTags {
+
+  final val FLATTENED = 5       // A flat name, generated by Flatten
+
+  final val TRAITSETTER = 6     // A Scala-2 trait setter, generated by AugmentScala2Traits
+
+  final val INITIALIZER = 24    // A mixin initializer method
+
+  final val AVOIDCLASH = 25     // Adds a suffix to avoid a name clash;
+                                // Used in FirstTransform for synthesized companion objects of classes
+                                // if they would clash with another value.
+
+  final val DIRECT = 26         // Used by ShortCutImplicits for the name of methods that
+                                // implement implicit function result types directly.
+
+  final val FIELD = 27          // Used by Memoize to tag the name of a class member field.
+
+  final val EXTMETH = 28        // Used by ExtensionMethods for the name of an extension method
+                                // implementing a value class method.
+
+  final val ADAPTEDCLOSURE = 29 // Used in Erasure to adapt closures over primitive types.
+
+  final val IMPLMETH = 30       // Used to define methods in implementation classes
+                                // (can probably be removed).
+
+  def nameTagToString(tag: Int): String = tag match {
+    case UTF8 => "UTF8"
+    case QUALIFIED => "QUALIFIED"
+    case FLATTENED => "FLATTENED"
+    case EXPANDED => "EXPANDED"
+    case EXPANDPREFIX => "EXPANDPREFIX"
+    case TRAITSETTER => "TRAITSETTER"
+    case UNIQUE => "UNIQUE"
+    case DEFAULTGETTER => "DEFAULTGETTER"
+    case VARIANT => "VARIANT"
+    case OUTERSELECT => "OUTERSELECT"
+
+    case SUPERACCESSOR => "SUPERACCESSOR"
+    case PROTECTEDACCESSOR => "PROTECTEDACCESSOR"
+    case PROTECTEDSETTER => "PROTECTEDSETTER"
+    case INITIALIZER => "INITIALIZER"
+    case AVOIDCLASH => "AVOIDCLASH"
+    case DIRECT => "DIRECT"
+    case FIELD => "FIELD"
+    case EXTMETH => "EXTMETH"
+    case ADAPTEDCLOSURE => "ADAPTEDCLOSURE"
+    case OBJECTCLASS => "OBJECTCLASS"
+
+    case SIGNED => "SIGNED"
+  }
+}