Redefine definesNewName

Make it a method of info instead of a convention over tags, because
it's less fragile that way.

Also, add UniqueName extractor.

Author: odersky

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

@@ -16,6 +16,7 @@ object NameExtractors {
 
   abstract class NameInfo extends DotClass {
     def tag: Int
+    def definesNewName: Boolean = false
     def mkString(underlying: TermName): String
     def map(f: SimpleTermName => SimpleTermName): NameInfo = this
   }
@@ -64,6 +65,7 @@ object NameExtractors {
   abstract class QualifiedNameExtractor(tag: Int, val separator: String, val infoString: String) extends NameExtractor(tag) {
     type ThisInfo = QualInfo
     case class QualInfo(val name: SimpleTermName) extends Info with QualifiedInfo {
+      override def definesNewName = true
       override def map(f: SimpleTermName => SimpleTermName): NameInfo = new QualInfo(f(name))
       override def toString = s"$infoString $name"
     }
@@ -89,9 +91,10 @@ object NameExtractors {
     def num: Int
   }
 
-  abstract class NumberedNameExtractor(tag: Int, val infoString: String) extends NameExtractor(tag) {
+  abstract class NumberedNameExtractor(tag: Int, val infoString: String) extends NameExtractor(tag) { self =>
     type ThisInfo = NumberedInfo
     case class NumberedInfo(val num: Int) extends Info with NameExtractors.NumberedInfo {
+      override def definesNewName = self.definesNewName
       override def toString = s"$infoString $num"
     }
     def apply(qual: TermName, num: Int) =
@@ -100,6 +103,14 @@ object NameExtractors {
       case DerivedTermName(underlying, info: this.NumberedInfo) => Some((underlying, info.num))
       case _ => None
     }
+    def definesNewName = false
+  }
+
+  class UniqueNameExtractor(sep: String) extends NumberedNameExtractor(UNIQUE, "Unique") {
+    val separator = if (sep.isEmpty) "$" else sep
+    override def definesNewName = !sep.isEmpty
+    def mkString(underlying: TermName, info: ThisInfo) =
+      underlying.toString + separator + info.num
   }
 
   object QualifiedName   extends QualifiedNameExtractor(QUALIFIED, ".", "Qualified")
@@ -148,8 +159,6 @@ object NameExtractors {
     def infoString: String = "Signed"
   }
 
-  def definesNewName(tag: Int) = tag <= TraitSetterName.tag
-
   def extractorOfTag(tag: Int) = extractors(tag)
 
   val separatorToQualified: Map[String, QualifiedNameExtractor] =

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

@@ -175,7 +175,7 @@ object Names {
      */
     def derived(info: NameInfo): TermName = {
       val ownTag = this.info.tag
-      if (ownTag < info.tag || definesNewName(info.tag)) add(info)
+      if (ownTag < info.tag || info.definesNewName) add(info)
       else if (ownTag > info.tag) rewrap(underlying.derived(info))
       else {
         assert(info == this.info)
@@ -185,15 +185,15 @@ object Names {
 
     def exclude(kind: NameExtractor): TermName = {
       val ownTag = this.info.tag
-      if (ownTag < kind.tag || definesNewName(ownTag)) this
+      if (ownTag < kind.tag || info.definesNewName) this
       else if (ownTag > kind.tag) rewrap(underlying.exclude(kind))
       else underlying
     }
 
     def is(kind: NameExtractor): Boolean = {
       val ownTag = this.info.tag
       ownTag == kind.tag ||
-      !definesNewName(ownTag) && ownTag > kind.tag && underlying.is(kind)
+      !info.definesNewName && ownTag > kind.tag && underlying.is(kind)
     }
 
     override def hashCode = System.identityHashCode(this)

compiler/src/dotty/tools/dotc/core/tasty/TastyFormat.scala

@@ -224,8 +224,9 @@ object TastyFormat {
   final val FLATTENED = 3
   final val EXPANDED = 4
   final val TRAITSETTER = 5
-  final val DEFAULTGETTER = 10
-  final val VARIANT = 11
+  final val UNIQUE = 10
+  final val DEFAULTGETTER = 11
+  final val VARIANT = 12
   final val SUPERACCESSOR = 20
   final val INITIALIZER = 21
   final val SHADOWED = 22