Use tags directly to store attributes

Author: nicolasstucki

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

@@ -10,18 +10,15 @@ import java.nio.charset.StandardCharsets
 object AttributePickler:
 
   def pickleAttributes(
-    attributes: List[String],
+    scala2StandardLibrary: Boolean,
     pickler: TastyPickler,
-    buf: TastyBuffer): Unit =
-      if attributes != Nil then
-        pickler.newSection(AttributesSection, buf)
-        for attribute <- attributes do
-          val bytes = attribute.getBytes(StandardCharsets.UTF_8).nn
-          val length = bytes.length
-          assert("[a-zA-Z0-9]+".r.matches(attribute), s"Malformed attribute: $attribute\n. Attribute must match [a-zA-Z0-9]+")
-          buf.writeNat(TastyFormat.FLAGattr)
-          buf.writeNat(length)
-          buf.writeBytes(bytes, length)
+    buf: TastyBuffer
+  ): Unit =
+    if scala2StandardLibrary then // or any other attribute is set
+      pickler.newSection(AttributesSection, buf)
+    // Pickle attributes
+    if scala2StandardLibrary then buf.writeNat(TastyFormat.SCALA2STANDARDLIBRARYattr)
+
   end pickleAttributes
 
 end AttributePickler

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

@@ -10,20 +10,16 @@ import java.nio.charset.StandardCharsets
 class AttributeUnpickler(reader: TastyReader):
   import reader._
 
-  private[tasty] lazy val attributes: List[String] = {
-    val attributesBuilder = List.newBuilder[String]
+  lazy val scala2StandardLibrary = {
+    var scala2StandardLibrary = false
     while (!isAtEnd) {
-      val kind = readNat()
-      assert(kind == TastyFormat.FLAGattr, "Malformed attribute kind")
-      val length = readNat()
-      val bytes = readBytes(length)
-      val attribute = new String(bytes, StandardCharsets.UTF_8)
-      assert("[a-zA-Z0-9]+".r.matches(attribute), s"Malformed attribute: $attribute\n. Attribute must match [a-zA-Z0-9]+")
-      attributesBuilder += attribute
+      readNat() match
+        case TastyFormat.SCALA2STANDARDLIBRARYattr =>
+          scala2StandardLibrary = true
+        case attribute =>
+          assert(false, "Unexpected attribute value: " + attribute)
     }
-    attributesBuilder.result()
+    scala2StandardLibrary
   }
 
-  def scala2Stdlib: Boolean = attributes.contains(TastyFormat.Scala2StandardLibraryAttribute)
-
 end AttributeUnpickler

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

@@ -230,10 +230,10 @@ class TastyPrinter(bytes: Array[Byte]) {
 
     def unpickle(reader: TastyReader, tastyName: NameTable): String = {
       sb.append(s" ${reader.endAddr.index - reader.currentAddr.index}")
-      val attributes = new AttributeUnpickler(reader).attributes
+      val attributeUnpickler = new AttributeUnpickler(reader)
       sb.append(s"  attributes bytes:\n")
-      for attribute <- attributes do
-        sb.append("  ").append(attribute).append("\n")
+      if attributeUnpickler.scala2StandardLibrary then
+        sb.append("    SCALA2STANDARDLIBRARYattr\n")
       sb.result
     }
   }

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

@@ -99,8 +99,8 @@ class TreeUnpickler(reader: TastyReader,
   /** Was unpickled class compiled with capture checks? */
   private var withCaptureChecks: Boolean = false
 
-  private val unpicklingScala2Lib =
-    attributeUnpicklerOpt.exists(_.scala2Stdlib)
+  private val unpicklingScala2Library =
+    attributeUnpicklerOpt.exists(_.scala2StandardLibrary)
 
   private def registerSym(addr: Addr, sym: Symbol) =
     symAtAddr(addr) = sym
@@ -614,7 +614,7 @@ class TreeUnpickler(reader: TastyReader,
       val rhsIsEmpty = nothingButMods(end)
       if (!rhsIsEmpty) skipTree()
       val (givenFlags0, annotFns, privateWithin) = readModifiers(end)
-      val givenFlags = if isClass && unpicklingScala2Lib then givenFlags0 | Scala2x | Scala2Tasty else givenFlags0
+      val givenFlags = if isClass && unpicklingScala2Library then givenFlags0 | Scala2x | Scala2Tasty else givenFlags0
       pickling.println(i"creating symbol $name at $start with flags ${givenFlags.flagsString}, isAbsType = $isAbsType, $ttag")
       val flags = normalizeFlags(tag, givenFlags, name, isAbsType, rhsIsEmpty)
       def adjustIfModule(completer: LazyType) =

compiler/src/dotty/tools/dotc/transform/Pickler.scala

@@ -16,7 +16,6 @@ import reporting.{ThrowingReporter, Profile, Message}
 import collection.mutable
 import util.concurrent.{Executor, Future}
 import compiletime.uninitialized
-import dotty.tools.tasty.TastyFormat.Scala2StandardLibraryAttribute
 
 object Pickler {
   val name: String = "pickler"
@@ -109,10 +108,10 @@ class Pickler extends Phase {
                 pickler, treePkl.buf.addrOfTree, treePkl.docString, tree,
                 scratch.commentBuffer)
 
-          val attributes =
-            if ctx.settings.YcompileScala2Library.value then List(Scala2StandardLibraryAttribute)
-            else Nil
-          AttributePickler.pickleAttributes(attributes, pickler, scratch.attributeBuffer)
+          AttributePickler.pickleAttributes(
+            ctx.settings.YcompileScala2Library.value,
+            pickler,
+            scratch.attributeBuffer)
 
           val pickled = pickler.assembleParts()
 

tasty/src/dotty/tools/tasty/TastyFormat.scala

@@ -270,7 +270,7 @@ Standard Section: "Comments" Comment*
 
 Standard Section: "Attributes" Attribute*
 ```none
-  Attribute     = FLAGattr UTF8             // attributes match the regex [a-zA-Z0-9]+
+  Attribute     = SCALA2STANDARDLIBRARYattr
 ```
 
 **************************************************************************************/
@@ -369,8 +369,6 @@ object TastyFormat {
   final val CommentsSection = "Comments"
   final val AttributesSection = "Attributes"
 
-  final val Scala2StandardLibraryAttribute = "Scala2StandardLibrary"
-
   /** Tags used to serialize names, should update [[TastyFormat$.nameTagToString]] if a new constant is added */
   class NameTags {
     final val UTF8 = 1               // A simple name in UTF8 encoding.
@@ -609,7 +607,7 @@ object TastyFormat {
 
   // Attribute tags
 
-  final val FLAGattr = 1
+  final val SCALA2STANDARDLIBRARYattr = 1
 
   /** Useful for debugging */
   def isLegalTag(tag: Int): Boolean =