Shrink reserved TASTy attribute categories

Author: nicolasstucki

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

@@ -3,7 +3,7 @@ package dotty.tools.dotc.core.tasty
 import dotty.tools.dotc.ast.{tpd, untpd}
 
 import dotty.tools.tasty.TastyBuffer
-import dotty.tools.tasty.TastyFormat, TastyFormat.AttributesSection
+import dotty.tools.tasty.TastyFormat.*
 
 object AttributePickler:
 
@@ -15,12 +15,12 @@ object AttributePickler:
     pickler.newSection(AttributesSection, buf)
 
     for tag <- attributes.booleanTags do
-      assert(tag < TastyFormat.firstStringAttrTag, "Not a boolean attribute tag: " + tag)
+      assert(isBooleanAttrTag(tag), "Not a boolean attribute tag: " + tag)
       buf.writeByte(tag)
 
-    assert(attributes.stringTagValues.exists(_._1 == TastyFormat.SOURCEFILEattr))
+    assert(attributes.stringTagValues.exists(_._1 == SOURCEFILEattr))
     for (tag, value) <- attributes.stringTagValues do
-      assert(TastyFormat.firstStringAttrTag <= tag && tag < TastyFormat.firstUnassignedAttrTag, "Not a string attribute tag: " + tag)
+      assert(isStringAttrTag(tag), "Not a string attribute tag: " + tag)
       val utf8Ref = pickler.nameBuffer.utf8Index(value)
       buf.writeByte(tag)
       buf.writeNat(utf8Ref.index)

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

@@ -5,7 +5,7 @@ import scala.language.unsafeNulls
 import scala.collection.immutable.BitSet
 import scala.collection.immutable.TreeMap
 
-import dotty.tools.tasty.{TastyFormat, TastyReader, TastyBuffer}
+import dotty.tools.tasty.{TastyFormat, TastyReader, TastyBuffer}, TastyFormat.{isBooleanAttrTag, isStringAttrTag}
 import dotty.tools.dotc.core.tasty.TastyUnpickler.NameTable
 
 class AttributeUnpickler(reader: TastyReader, nameAtRef: NameTable):
@@ -17,9 +17,9 @@ class AttributeUnpickler(reader: TastyReader, nameAtRef: NameTable):
 
     while !isAtEnd do
       val tag = readByte()
-      if tag < TastyFormat.firstStringAttrTag then
+      if isBooleanAttrTag(tag) then
         booleanTags += tag
-      else if tag < TastyFormat.firstUnassignedAttrTag then
+      else if isStringAttrTag(tag) then
         val utf8Ref = readNameRef()
         val value = nameAtRef(utf8Ref).toString
         stringTagValue += tag -> value

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

@@ -232,8 +232,8 @@ class TastyPrinter(bytes: Array[Byte]) {
       while !isAtEnd do
         val tag = readByte()
         sb.append("  ").append(attributeTagToString(tag))
-        if tag < firstStringAttrTag then ()
-        else if tag < firstUnassignedAttrTag then
+        if isBooleanAttrTag(tag) then ()
+        else if isStringAttrTag(tag) then
           val utf8Ref = readNameRef()
           val value = nameAtRef(utf8Ref).toString
           sb.append(nameStr(s" ${utf8Ref.index} [$value]"))

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

@@ -282,10 +282,13 @@ Standard Section: "Attributes" Attribute*
                   SOURCEFILEattr Utf8Ref
 ```
 
-Note: Attribute tags are grouped into 2 categories that determine what follows, and thus allow to compute the size of the tagged tree in a generic way.
+Note: Attribute tags are grouped into categories that determine what follows, and thus allow to compute the size of the tagged tree in a generic way.
+      Unassigned categories can be used to extend and existing category or to add new kinds of attributes
 ```none
-  Attribute Category 1 (tags 1-64)  :  tag
-  Attribute Category 2 (tags 65-128):  tag Utf8Ref
+  Attribute Category 1 (tags 1-32)  :  tag
+  Attribute Category 2 (tags 33-128): // not assigned yet
+  Attribute Category 3 (tags 129-160):  tag Utf8Ref
+  Attribute Category 4 (tags 161-255): // not assigned yet
 ```
 
 **************************************************************************************/
@@ -617,21 +620,24 @@ object TastyFormat {
 
   // Attributes tags
 
-  // Attr Cat. 1: tag
-  final val firstBooleanAttrTag = SCALA2STANDARDLIBRARYattr
+  // Attribute Category 1 (tags 1-32)  :  tag
+  def isBooleanAttrTag(tag: Int): Boolean = 1 <= tag && tag <= 32
   final val SCALA2STANDARDLIBRARYattr = 1
   final val EXPLICITNULLSattr = 2
   final val CAPTURECHECKEDattr = 3
   final val WITHPUREFUNSattr = 4
   final val JAVAattr = 5
   final val OUTLINEattr = 6
 
-  // Attr Cat. 2: tag UTF8
-  final val firstStringAttrTag = SOURCEFILEattr
-  final val SOURCEFILEattr = 128
+  // Attribute Category 2 (tags 33-128): unassigned
 
-  // Attr Cat. 3: unassigned
-  final val firstUnassignedAttrTag = 129
+  // Attribute Category 3 (tags 129-160):  tag Utf8Ref
+  def isStringAttrTag(tag: Int): Boolean = 129 <= tag && tag <= 160
+  final val SOURCEFILEattr = 129
+
+  // Attribute Category 4 (tags 161-255): unassigned
+
+  // end of Attributes tags
 
 
   /** Useful for debugging */