Polish and document NameKinds

Author: odersky

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

@@ -16,6 +16,7 @@ object NameKinds {
 
   @sharable private val simpleNameKinds = new mutable.HashMap[Int, ClassifiedNameKind]
   @sharable private val qualifiedNameKinds = new mutable.HashMap[Int, QualifiedNameKind]
+  @sharable private val numberedNameKinds = new mutable.HashMap[Int, NumberedNameKind]
   @sharable private val uniqueNameKinds = new mutable.HashMap[String, UniqueNameKind]
 
   /** A class for the info stored in a derived name */
@@ -25,39 +26,65 @@ object NameKinds {
     def map(f: SimpleName => SimpleName): NameInfo = this
   }
 
-  /** The kind of a derived name info */
+  /** An abstract base class of classes that define the kind of a derived name info */
   abstract class NameKind(val tag: Int) extends DotClass { self =>
+
+    /** The info class defined by this kind */
     type ThisInfo <: Info
+
+    /** A simple info type; some subclasses of Kind define more refined versions */
     class Info extends NameInfo { this: ThisInfo =>
       def kind = self
       def mkString(underlying: TermName) = self.mkString(underlying, this)
       override def toString = infoString
     }
+
+    /** Does this kind define logically a new name? Tested by the `rewrite` and `collect`
+     *  combinators of names.
+     */
     def definesNewName = false
+
+    /** Unmangle simple name `name` into a name of this kind, or return
+     *  original name if this is not possible.
+     */
     def unmangle(name: SimpleName): TermName = name
+
+    /** Turn a name of this kind consisting of an `underlying` prefix
+     *  and the given `info` into a string.
+     */
     def mkString(underlying: TermName, info: ThisInfo): String
+
+    /** A string used for displaying the structure of a name */
     def infoString: String
   }
 
+  /** The kind of SimpleNames */
   object SimpleNameKind extends NameKind(UTF8) { self =>
     type ThisInfo = Info
     val info = new Info
     def mkString(underlying: TermName, info: ThisInfo) = unsupported("mkString")
     def infoString = unsupported("infoString")
   }
 
+  /** The kind of names that add a simple classification to an underlying name.
+   */
   abstract class ClassifiedNameKind(tag: Int, val infoString: String) extends NameKind(tag) {
     type ThisInfo = Info
     val info = new Info
-    def apply(qual: TermName) =
-      qual.derived(info)
+
+    /** Build a new name of this kind from an underlying name */
+    def apply(underlying: TermName) = underlying.derived(info)
+
+    /** Extractor operation for names of this kind */
     def unapply(name: DerivedName): Option[TermName] =  name match {
       case DerivedName(underlying, `info`) => Some(underlying)
       case _ => None
     }
+
     simpleNameKinds(tag) = this
   }
 
+  /** The kind of names that get formed by adding a prefix to an underlying name */
   class PrefixNameKind(tag: Int, prefix: String, optInfoString: String = "")
   extends ClassifiedNameKind(tag, if (optInfoString.isEmpty) s"Prefix $prefix" else optInfoString) {
     def mkString(underlying: TermName, info: ThisInfo) =
@@ -67,6 +94,7 @@ object NameKinds {
       else name
   }
 
+  /** The kind of names that get formed by appending a suffix to an underlying name */
   class SuffixNameKind(tag: Int, suffix: String, optInfoString: String = "")
   extends ClassifiedNameKind(tag, if (optInfoString.isEmpty) s"Suffix $suffix" else optInfoString) {
     def mkString(underlying: TermName, info: ThisInfo) = underlying.toString ++ suffix
@@ -75,17 +103,24 @@ object NameKinds {
       else name
   }
 
+  /** A base trait for infos that define an additional selector name */
   trait QualifiedInfo extends NameInfo {
     val name: SimpleName
   }
 
+  /** The kind of qualified names, consisting of an underlying name as a prefix,
+   *  followed by a separator, followed by a simple selector name.
+   *
+   *  A qualified names always constitutes a new name, different from its underlying name.
+   */
   class QualifiedNameKind(tag: Int, val separator: String)
   extends NameKind(tag) {
     type ThisInfo = QualInfo
     case class QualInfo(val name: SimpleName) extends Info with QualifiedInfo {
       override def map(f: SimpleName => SimpleName): NameInfo = new QualInfo(f(name))
       override def toString = s"$infoString $name"
     }
+
     def apply(qual: TermName, name: SimpleName): TermName =
       qual.derived(new QualInfo(name))
 
@@ -107,11 +142,13 @@ object NameKinds {
 
     def mkString(underlying: TermName, info: ThisInfo) =
       s"$underlying$separator${info.name}"
+
     def infoString = s"Qualified $separator"
 
     qualifiedNameKinds(tag) = this
   }
 
+  /** An extractor for qualified names of an arbitrary kind */
   object AnyQualifiedName {
     def unapply(name: DerivedName): Option[(TermName, SimpleName)] = name match {
       case DerivedName(qual, info: QualifiedInfo) =>
@@ -120,10 +157,12 @@ object NameKinds {
     }
   }
 
+  /** A base trait for infos that contain a number */
   trait NumberedInfo extends NameInfo {
     def num: Int
   }
 
+  /** The kind of numbered names consisting of an underlying name and a number */
   abstract class NumberedNameKind(tag: Int, val infoString: String) extends NameKind(tag) { self =>
     type ThisInfo = NumberedInfo
     case class NumberedInfo(val num: Int) extends Info with NameKinds.NumberedInfo {
@@ -142,29 +181,40 @@ object NameKinds {
           name.slice(i - separator.length, i).toString == separator) i
       else -1
     }
+
+    numberedNameKinds(tag) = this
   }
 
+  /** An extractor for numbered names of arbitrary kind */
   object AnyNumberedName {
     def unapply(name: DerivedName): Option[(TermName, Int)] = name match {
       case DerivedName(qual, info: NumberedInfo) => Some((qual, info.num))
       case _ => None
     }
   }
 
+  /** The kind of unique names that consist of an underlying name (can be empty),
+   *  a separator indicating the class of unique name, and a unique number.
+   *
+   *  A unique names always constitutes a new name, different from its underlying name.
+   */
   case class UniqueNameKind(val separator: String)
   extends NumberedNameKind(UNIQUE, s"Unique $separator") {
     override def definesNewName = true
+
     def mkString(underlying: TermName, info: ThisInfo) = {
       val safePrefix = str.sanitize(underlying.toString + separator)
       safePrefix + info.num
     }
 
+    /** Generate fresh unique name of this kind with given prefix name */
     def fresh(prefix: TermName = EmptyTermName)(implicit ctx: Context): TermName =
       ctx.freshNames.newName(prefix, this)
 
     uniqueNameKinds(separator) = this
   }
 
+  /** An extractor for unique names of arbitrary kind */
   object AnyUniqueName {
     def unapply(name: DerivedName): Option[(TermName, String, Int)] = name match {
       case DerivedName(qual, info: NumberedInfo) =>
@@ -176,10 +226,16 @@ object NameKinds {
     }
   }
 
-  val QualifiedName           = new QualifiedNameKind(QUALIFIED, ".")
-  val FlatName                = new QualifiedNameKind(FLATTENED, "$")
-  val ExpandPrefixName        = new QualifiedNameKind(EXPANDPREFIX, "$")
+  /** Names of the form `prefix . name` */
+  val QualifiedName = new QualifiedNameKind(QUALIFIED, ".")
+
+  /** Names of the form `prefix $ name` that are constructed as a result of flattening */
+  val FlatName = new QualifiedNameKind(FLATTENED, "$")
+
+  /** Names of the form `prefix $ name` that are prefixes of expanded names */
+  val ExpandPrefixName = new QualifiedNameKind(EXPANDPREFIX, "$")
 
+  /** Expanded names of the form `prefix $$ name`. */
   val ExpandedName = new QualifiedNameKind(EXPANDED, str.EXPAND_SEPARATOR) {
     private val FalseSuper = termName("$$super")
     private val FalseSuperLength = FalseSuper.length
@@ -199,13 +255,16 @@ object NameKinds {
     }
   }
 
-  val TraitSetterName         = new QualifiedNameKind(TRAITSETTER, str.TRAIT_SETTER_SEPARATOR)
+  /** Expanded names of the form `prefix $_setter_$ name`. These only occur in Scala2. */
+  val TraitSetterName = new QualifiedNameKind(TRAITSETTER, str.TRAIT_SETTER_SEPARATOR)
 
+  /** Unique names of the form `prefix $ n` or `$ n $` */
   val UniqueName = new UniqueNameKind("$") {
     override def mkString(underlying: TermName, info: ThisInfo) =
       if (underlying.isEmpty) "$" + info.num + "$" else super.mkString(underlying, info)
   }
 
+  /** Other unique names */
   val InlineAccessorName      = new UniqueNameKind("$_inlineAccessor_$")
   val TempResultName          = new UniqueNameKind("ev$")
   val EvidenceParamName       = new UniqueNameKind("evidence$")
@@ -222,6 +281,9 @@ object NameKinds {
   val SkolemName              = new UniqueNameKind("?")
   val LiftedTreeName          = new UniqueNameKind("liftedTree")
 
+  /** A kind of unique extension methods; Unlike other unique names, these can be
+   *  unmangled.
+   */
   val UniqueExtMethName = new UniqueNameKind("$extension") {
     override def unmangle(name: SimpleName): TermName = {
       val i = skipSeparatorAndNum(name, separator)
@@ -234,6 +296,7 @@ object NameKinds {
     }
   }
 
+  /** Kinds of unique names generated by the pattern matcher */
   val PatMatStdBinderName     = new UniqueNameKind("x")
   val PatMatPiName            = new UniqueNameKind("pi") // FIXME: explain what this is
   val PatMatPName             = new UniqueNameKind("p")  // FIXME: explain what this is
@@ -242,6 +305,7 @@ object NameKinds {
   val PatMatMatchFailName     = new UniqueNameKind("matchFail")
   val PatMatSelectorName      = new UniqueNameKind("selector")
 
+  /** The kind of names of default argument getters */
   object DefaultGetterName extends NumberedNameKind(DEFAULTGETTER, "DefaultGetter") {
     def mkString(underlying: TermName, info: ThisInfo) = {
       val prefix = if (underlying.isConstructorName) nme.DEFAULT_GETTER_INIT else underlying
@@ -260,11 +324,9 @@ object NameKinds {
     }
   }
 
+  /** The kind of names that also encode a variance: 0 for contravariance, 1 for covariance. */
   object VariantName extends NumberedNameKind(VARIANT, "Variant") {
-    val varianceToPrefix = Map(-1 -> '-', 0 -> '=', 1 -> '+')
-    def mkString(underlying: TermName, info: ThisInfo) = {
-      varianceToPrefix(info.num).toString + underlying
-    }
+    def mkString(underlying: TermName, info: ThisInfo) = "-+"(info.num).toString + underlying
   }
 
   /** Names of the form N_<outer>. Emitted by inliner, replaced by outer path
@@ -289,9 +351,9 @@ object NameKinds {
   val ModuleVarName = new SuffixNameKind(OBJECTVAR, "$module")
   val ModuleClassName = new SuffixNameKind(OBJECTCLASS, "$", optInfoString = "ModuleClass")
 
+  /** A name together with a signature. Used in Tasty trees. */
   object SignedName extends NameKind(63) {
 
-    /** @param parts  resultSig followed by paramsSig */
     case class SignedInfo(sig: Signature) extends Info {
       override def toString = s"$infoString $sig"
     }
@@ -308,10 +370,12 @@ object NameKinds {
     def infoString: String = "Signed"
   }
 
+  /** Possible name kinds of a method that comes from Scala2 pickling info. */
   val Scala2MethodNameKinds: List[NameKind] =
     List(DefaultGetterName, ExtMethName, UniqueExtMethName, ProtectedAccessorName, ProtectedSetterName)
 
   def simpleNameKindOfTag      : collection.Map[Int, ClassifiedNameKind] = simpleNameKinds
   def qualifiedNameKindOfTag   : collection.Map[Int, QualifiedNameKind]  = qualifiedNameKinds
+  def numberedNameKindOfTag    : collection.Map[Int, NumberedNameKind]   = numberedNameKinds
   def uniqueNameKindOfSeparator: collection.Map[String, UniqueNameKind]  = uniqueNameKinds
 }

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

@@ -128,15 +128,24 @@ object NameOps {
 
     def errorName: N = likeSpaced(name ++ nme.ERROR)
 
+    /** Map variance value -1, +1 to 0, 1 */
+    private def varianceToNat(v: Int) = (v + 1) / 2
+
+    /** Map 0, 1 to variance value -1, +1 */
+    private def natToVariance(n: Int) = n * 2 - 1
 
     /** Name with variance prefix: `+` for covariant, `-` for contravariant */
-    def withVariance(v: Int): N =
-      likeSpaced { VariantName(name.exclude(VariantName).toTermName, v) }
+    def withVariance(v: Int): N = {
+      val underlying = name.exclude(VariantName)
+      likeSpaced(
+          if (v == 0) underlying
+          else VariantName(underlying.toTermName, varianceToNat(v)))
+    }
 
     /** The variance as implied by the variance prefix, or 0 if there is
      *  no variance prefix.
      */
-    def variance = name.collect { case VariantName(_, n) => n }.getOrElse(0)
+    def variance = name.collect { case VariantName(_, n) => natToVariance(n) }.getOrElse(0)
 
     def freshened(implicit ctx: Context): N = likeSpaced {
       name.toTermName match {

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

@@ -84,13 +84,15 @@ object Names {
     }
 
     /** Apply rewrite rule given by `f` to some part of this name, skipping and rewrapping
-     *  other decorators. Stops at first qualified name that's encountered.
+     *  other decorators.
+     *  Stops at derived names whose kind has `definesNewName = true`.
      *  If `f` does not apply to any part, return name unchanged.
      */
     def rewrite(f: PartialFunction[Name, Name]): ThisName
 
     /** If partial function `f` is defined for some part of this name, apply it
-     *  in a Some, otherwise None. Stops at first qualified name that's encountered.
+     *  in a Some, otherwise None.
+     *  Stops at derived names whose kind has `definesNewName = true`.
      */
     def collect[T](f: PartialFunction[Name, T]): Option[T]
 

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

@@ -34,14 +34,6 @@ import scala.annotation.tailrec
 case class Signature(paramsSig: List[TypeName], resSig: TypeName) {
   import Signature._
 
-/* FIXME does not compile under dotty, we get a missing param error
-  def checkUnqual(name: TypeName) = name mapParts { part =>
-    assert(!part.contains('.'), name)
-    part
-  }
-  paramsSig.foreach(checkUnqual)
-  checkUnqual(resSig)
-*/
   /** Two names are consistent if they are the same or one of them is tpnme.Uninstantiated */
   private def consistent(name1: TypeName, name2: TypeName) =
     name1 == name2 || name1 == tpnme.Uninstantiated || name2 == tpnme.Uninstantiated

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

@@ -70,8 +70,6 @@ class NameBuffer extends TastyBuffer(10000) {
           writeNat(num)
           if (!original.isEmpty) writeNameRef(original)
         }
-      case VariantName(original, sign) =>
-        withLength { writeNameRef(original); writeNat(sign + 1) }
       case AnyNumberedName(original, num) =>
         withLength { writeNameRef(original); writeNat(num) }
       case SignedName(original, Signature(params, result)) =>

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

@@ -57,12 +57,8 @@ class TastyUnpickler(reader: TastyReader) {
         val originals = until(end)(readName())
         val original = if (originals.isEmpty) EmptyTermName else originals.head
         uniqueNameKindOfSeparator(separator)(original, num)
-      case DEFAULTGETTER =>
-        DefaultGetterName(readName(), readNat())
-      case VARIANT =>
-        VariantName(readName(), readNat() - 1)
-      case OUTERSELECT =>
-        OuterSelectName(readName(), readNat())
+      case DEFAULTGETTER | VARIANT | OUTERSELECT =>
+        numberedNameKindOfTag(tag)(readName(), readNat())
       case SIGNED =>
         val original = readName()
         val result = readName().toTypeName