Changes to Tasty format

Use fewer length fields in type encodings.

- create new category of tags that take exactly one argument tree.
- avoid using length where a tag fits in one of theopther categories.

5 files changed, 74 insertions, 80 deletions

diff --git a/src/dotty/tools/dotc/TypeErasure.scala b/src/dotty/tools/dotc/core/TypeErasure.scala
index a45e29287..a45e29287 100644
--- a/src/dotty/tools/dotc/TypeErasure.scala
+++ b/src/dotty/tools/dotc/core/TypeErasure.scala
diff --git a/src/dotty/tools/dotc/core/pickling/PickleFormat.scala b/src/dotty/tools/dotc/core/pickling/PickleFormat.scala
index 1a79ad08e..3338c355e 100644
--- a/src/dotty/tools/dotc/core/pickling/PickleFormat.scala
+++ b/src/dotty/tools/dotc/core/pickling/PickleFormat.scala
@@ -55,7 +55,7 @@ Standard-Section: "ASTs" TopLevelStat*
                                         Modifier*
                   TYPEDEF        Length NameRef (Type | Template) Modifier*
                   IMPORT         Length qual_Term Selector*
-  Selector      = IMPORTED       Length name_NameRef
+  Selector      = IMPORTED              name_NameRef
                   RENAMED        Length from_NameRef to_NameRef
                                  // Imports are for scala.meta, they are not used in the backend
 
@@ -65,14 +65,14 @@ Standard-Section: "ASTs" TopLevelStat*
   Template      = TEMPLATE       Length TypeParam* Param* Parent* Self? Stat* // Stat* always starts with the primary constructor.
   Parent        = Application
                   Type
-  Self          = SELFDEF        Length selfName_NameRef selfType_Type
+  Self          = SELFDEF               selfName_NameRef selfType_Type
 
   Term          = Path
                   Application
                   IDENT                 NameRef Type     // used when ident’s type is not a TermRef
                   SELECT                possiblySigned_NameRef qual_Term
+                  NEW                   cls_Type
                   SUPER          Length this_Term mixinTrait_Type?
-                  NEW            Length cls_Type
                   PAIR           Length left_Term right_Term
                   TYPED          Length expr_Term ascription_Type
                   NAMEDARG       Length paramName_NameRef arg_Term
@@ -94,7 +94,7 @@ Standard-Section: "ASTs" TopLevelStat*
 
                   TYPEAPPLY      Length fn_Term arg_Type*
   CaseDef       = CASEDEF        Length pat_Term rhs_Tree guard_Tree?
-  ImplicitArg   = IMPLICITARG    Length arg_Term
+  ImplicitArg   = IMPLICITARG           arg_Term
   ASTRef        = Nat                          		// byte position in AST payload
 
   Path          = Constant
@@ -102,7 +102,7 @@ Standard-Section: "ASTs" TopLevelStat*
                   TERMREFsymbol         sym_ASTRef qual_Type
                   TERMREFpkg            fullyQualified_NameRef
                   TERMREF               possiblySigned_NameRef qual_Type
-                  THIS           Length clsRef_Type
+                  THIS                  clsRef_Type
                   SKOLEMtype            refinedType_ASTRef
                   SHARED                path_ASTRef
 
@@ -119,8 +119,8 @@ Standard-Section: "ASTs" TopLevelStat*
                   DOUBLEconst           LongInt
                   STRINGconst           NameRef
                   NULLconst
-                  CLASSconst     Length Type
-                  ENUMconst      Length Path
+                  CLASSconst            Type
+                  ENUMconst             Path
 
   Type          = Path
                   TYPEREFdirect         sym_ASTRef
@@ -147,10 +147,10 @@ Standard-Section: "ASTs" TopLevelStat*
   NameType      = paramName_NameRef typeOrBounds_ASTRef
 
   Modifier      = PRIVATE
-                  INTERNAL						// package private
+                  INTERNAL						  // package private
                   PROTECTED
-                  PRIVATEqualified     Length qualifier_Type		// will be dropped
-                  PROTECTEDqualified   Length qualifier_Type 	// will be dropped
+                  PRIVATEqualified     qualifier_Type		// will be dropped
+                  PROTECTEDqualified   qualifier_Type 	// will be dropped
                   ABSTRACT
                   FINAL
                   SEALED
@@ -158,33 +158,34 @@ Standard-Section: "ASTs" TopLevelStat*
                   IMPLICIT
                   LAZY
                   OVERRIDE
-                  INLINE              // macro
-                  ABSOVERRIDE					// abstract override
-                  STATIC						// mapped to static Java member
-                  MODULE						// an object or its class
-                  TRAIT            // a trait
-                  LOCAL						// private[this] or protected[this]
-                  SYNTHETIC					// generated by Scala compiler
-                  ARTIFACT						// to be tagged Java Synthetic
-                  MUTABLE 						// a var
-                  LABEL						// method generated as a label
-                  FIELDaccessor					// getter or setter
-                  CASEaccessor					// getter for case class param
-                  COVARIANT					// type param marked “+”
-                  CONTRAVARIANT					// type param marked “-”
-                  SCALA2X						// Imported from Scala2.x
-                  DEFAULTparameterized				// Method with default params
-                  DEFAULTinit					// variable with “_” initializer
-                  INSUPERCALL         // defined in the argument of a constructor supercall
+                  INLINE                // macro
+                  ABSOVERRIDE					  // abstract override
+                  STATIC						    // mapped to static Java member
+                  MODULE						    // an object or its class
+                  TRAIT                 // a trait
+                  LOCAL						      // private[this] or protected[this]
+                  SYNTHETIC					    // generated by Scala compiler
+                  ARTIFACT						  // to be tagged Java Synthetic
+                  MUTABLE 						  // a var
+                  LABEL						      // method generated as a label
+                  FIELDaccessor				  // getter or setter
+                  CASEaccessor			    // getter for case class param
+                  COVARIANT					    // type param marked “+”
+                  CONTRAVARIANT			    // type param marked “-”
+                  SCALA2X						    // Imported from Scala2.x
+                  DEFAULTparameterized  // Method with default params
+                  DEFAULTinit					  // variable with “_” initializer
+                  INSUPERCALL           // defined in the argument of a constructor supercall
                   Annotation
-  Annotation    = ANNOTATION     Length tycon_Symbol fullAnnotation_Term
+  Annotation    = ANNOTATION     Length tycon_Type fullAnnotation_Term
 
-Note: Tree tags are grouped into 4 categories that determine what follows, and thus allow to compute the size of the tagged tree in a generic way.
+Note: Tree tags are grouped into 5 categories that determine what follows, and thus allow to compute the size of the tagged tree in a generic way.
 
-	Category 1 (tags 0-63)   :	tag
-	Category 2 (tags 64-99)  :	tag Nat
-	Category 3 (tags 100-127):	tag Nat AST
-	Category 4 (tags 128-255):  tag Length <payload>
+  Category 1 (tags 0-63)   :  tag
+  Category 2 (tags 64-95)  :  tag Nat
+  Category 3 (tags 96-111) :  tag AST
+  Category 4 (tags 112-127):  tag Nat AST
+  Category 5 (tags 128-255):  tag Length <payload>
 
 Standard Section: "Positions" sourceLength_Nat Assoc*
 
@@ -271,13 +272,23 @@ object PickleFormat {
   final val FLOATconst = 75
   final val DOUBLEconst = 76
   final val STRINGconst = 77
-
-  final val IDENT = 100
-  final val SELECT = 101
-  final val TERMREFsymbol = 102
-  final val TERMREF = 103
-  final val TYPEREFsymbol = 104
-  final val TYPEREF = 105
+  final val IMPORTED = 78
+  
+  final val THIS = 96
+  final val CLASSconst = 97
+  final val ENUMconst = 98
+  final val NEW = 99
+  final val IMPLICITarg = 100
+  final val PRIVATEqualified = 101
+  final val PROTECTEDqualified = 102
+
+  final val IDENT = 112
+  final val SELECT = 113
+  final val TERMREFsymbol = 114
+  final val TERMREF = 115
+  final val TYPEREFsymbol = 116
+  final val TYPEREF = 117
+  final val SELFDEF = 118
 
   final val PACKAGE = 128
   final val VALDEF = 129
@@ -287,11 +298,9 @@ object PickleFormat {
   final val TYPEPARAM = 133
   final val PARAMS = 134
   final val PARAM = 136
-  final val IMPORTED = 137
   final val RENAMED = 138
   final val APPLY = 139
   final val TYPEAPPLY = 140
-  final val NEW = 141
   final val PAIR = 142
   final val TYPED = 143
   final val NAMEDARG = 144
@@ -309,13 +318,8 @@ object PickleFormat {
   final val UNAPPLY = 156
   final val ANNOTATED = 157
   final val CASEDEF = 158
-  final val IMPLICITarg = 159
   final val TEMPLATE = 160
-  final val SELFDEF = 161
-  final val THIS = 162
   final val SUPER = 163
-  final val CLASSconst = 164
-  final val ENUMconst = 165
   final val SUPERtype = 166
   final val REFINEDtype = 167
   final val APPLIEDtype = 168
@@ -327,13 +331,11 @@ object PickleFormat {
   final val METHODtype = 174
   final val POLYtype = 175
   final val PARAMtype = 176
-  final val IMPLICITARG = 177
   final val ANNOTATION = 178
-  final val PRIVATEqualified = 179
-  final val PROTECTEDqualified = 180
 
   final val firstSimpleTreeTag = EMPTYTREE
   final val firstNatTreeTag = SHARED
+  final val firstASTTreeTag = THIS
   final val firstNatASTTreeTag = IDENT
   final val firstLengthTreeTag = PACKAGE
 
@@ -490,7 +492,6 @@ object PickleFormat {
     case POLYtype => "POLYtype"
     case METHODtype => "METHODtype"
     case PARAMtype => "PARAMtype"
-    case IMPLICITARG => "IMPLICITARG"
     case ANNOTATION => "ANNOTATION"
     case PRIVATEqualified => "PRIVATEqualified"
     case PROTECTEDqualified => "PROTECTEDqualified"
diff --git a/src/dotty/tools/dotc/core/pickling/TastyPrinter.scala b/src/dotty/tools/dotc/core/pickling/TastyPrinter.scala
index 38dac2c32..3311fc683 100644
--- a/src/dotty/tools/dotc/core/pickling/TastyPrinter.scala
+++ b/src/dotty/tools/dotc/core/pickling/TastyPrinter.scala
@@ -62,11 +62,9 @@ class TastyPrinter(bytes: Array[Byte])(implicit ctx: Context) {
           val end = currentAddr + len
           def printTrees() = until(end)(printTree())
           tag match {
-            case IMPORTED => 
-              printName()
             case RENAMED =>
               printName(); printName()
-            case VALDEF | DEFDEF | TYPEDEF | TYPEPARAM | PARAM | NAMEDARG | SELFDEF | BIND => 
+            case VALDEF | DEFDEF | TYPEDEF | TYPEPARAM | PARAM | NAMEDARG | BIND => 
               printName(); printTrees()
             case REFINEDtype =>
               printTree(); printName(); printTrees()
@@ -87,14 +85,16 @@ class TastyPrinter(bytes: Array[Byte])(implicit ctx: Context) {
         }
         else if (tag >= firstNatASTTreeTag) { 
           tag match {
-            case IDENT | SELECT | TERMREF | TYPEREF => printName()
+            case IDENT | SELECT | TERMREF | TYPEREF | SELFDEF => printName()
             case _ => printNat() 
           }
           printTree()
         }
+        else if (tag >= firstASTTreeTag) 
+          printTree()
         else if (tag >= firstNatTreeTag) 
           tag match {
-            case TERMREFpkg | TYPEREFpkg | STRINGconst => printName()
+            case TERMREFpkg | TYPEREFpkg | STRINGconst | IMPORTED => printName()
             case _ => printNat()
           }
         indent -= 2
diff --git a/src/dotty/tools/dotc/core/pickling/TreePickler.scala b/src/dotty/tools/dotc/core/pickling/TreePickler.scala
index 750c7bda6..b8f031ec5 100644
--- a/src/dotty/tools/dotc/core/pickling/TreePickler.scala
+++ b/src/dotty/tools/dotc/core/pickling/TreePickler.scala
@@ -103,10 +103,10 @@ class TreePickler(pickler: TastyPickler) {
         writeByte(NULLconst)
       case ClazzTag =>
         writeByte(CLASSconst)
-        withLength { pickleType(c.typeValue) }
+        pickleType(c.typeValue)
       case EnumTag =>
         writeByte(ENUMconst)
-        withLength { pickleType(c.symbolValue.termRef) }
+        pickleType(c.symbolValue.termRef)
     }
 
     def pickleType(tpe0: Type, richTypes: Boolean = false): Unit = try {
@@ -165,7 +165,7 @@ class TreePickler(pickler: TastyPickler) {
         pickleName(tpe.name); pickleType(tpe.prefix)
       case tpe: ThisType =>
         writeByte(THIS)
-        withLength { pickleType(tpe.tref) }
+        pickleType(tpe.tref)
       case tpe: SuperType =>
         writeByte(SUPERtype)
         withLength { pickleType(tpe.thistpe); pickleType(tpe.supertpe)}
@@ -302,7 +302,7 @@ class TreePickler(pickler: TastyPickler) {
         }
       case New(tpt) =>
         writeByte(NEW)
-        withLength { pickleTpt(tpt) }
+        pickleTpt(tpt)
       case Pair(left, right) =>
         writeByte(PAIR)
         withLength { pickleTree(left); pickleTree(right) }
@@ -357,8 +357,8 @@ class TreePickler(pickler: TastyPickler) {
         withLength { 
           pickleTree(fun)
           for (implicitArg <- implicits) {
-            writeByte(IMPLICITARG)
-            withLength { pickleTree(implicitArg) }
+            writeByte(IMPLICITarg)
+            pickleTree(implicitArg)
           }
           pickleType(tree.tpe)
           patterns.foreach(pickleTree) 
@@ -390,10 +390,8 @@ class TreePickler(pickler: TastyPickler) {
           val cinfo @ ClassInfo(_, _, _, _, selfInfo) = tree.symbol.owner.info
           if ((selfInfo ne NoType) || !tree.self.isEmpty) {
             writeByte(SELFDEF)
-            withLength {
-              pickleName(tree.self.name)
-              pickleType(cinfo.selfType)
-            }
+            pickleName(tree.self.name)
+            pickleType(cinfo.selfType)
           }
           pickleStats(tree.constr :: rest)
         }
@@ -407,7 +405,7 @@ class TreePickler(pickler: TastyPickler) {
               withLength { pickleName(from); pickleName(to) }
             case Ident(name) =>
               writeByte(IMPORTED)
-              withLength { pickleName(name) }
+              pickleName(name)
           }
         }
       case PackageDef(pid, stats) =>
@@ -460,7 +458,7 @@ class TreePickler(pickler: TastyPickler) {
       val privateWithin = sym.privateWithin
       if (privateWithin.exists) {
         writeByte(if (flags is Protected) PROTECTEDqualified else PRIVATEqualified)
-        withLength { pickleType(privateWithin.typeRef) }
+        pickleType(privateWithin.typeRef)
       }
       if (flags is Private) writeByte(PRIVATE)
       if (flags is Protected) if (!privateWithin.exists) writeByte(PROTECTED)
diff --git a/src/dotty/tools/dotc/core/pickling/TreeUnpickler.scala b/src/dotty/tools/dotc/core/pickling/TreeUnpickler.scala
index edd951a9d..4890e14ef 100644
--- a/src/dotty/tools/dotc/core/pickling/TreeUnpickler.scala
+++ b/src/dotty/tools/dotc/core/pickling/TreeUnpickler.scala
@@ -72,6 +72,7 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, roots: Set[
     def skipTree(tag: Int): Unit =
       if (tag >= firstLengthTreeTag) goto(readEnd())
       else if (tag >= firstNatASTTreeTag) { readNat(); skipTree() }
+      else if (tag >= firstASTTreeTag) skipTree()
       else if (tag >= firstNatTreeTag) readNat()
     def skipTree(): Unit = skipTree(readByte())
     
@@ -130,8 +131,6 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, roots: Set[
         
         val result =
           (tag: @switch) match {
-            case THIS =>
-              ThisType.raw(readType().asInstanceOf[TypeRef])
             case SUPERtype =>
               SuperType(readType(), readType())
             case REFINEDtype =>
@@ -190,10 +189,8 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, roots: Set[
                 case binder: MethodType => MethodParam(binder, readNat())
               }
             case CLASSconst =>
-              readEnd()
               ConstantType(Constant(readType()))
             case ENUMconst =>
-              readEnd()
               ConstantType(Constant(readTermRef().termSymbol))
           }
         assert(currentAddr == end, s"$start $currentAddr $end ${astTagToString(tag)}")
@@ -228,6 +225,8 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, roots: Set[
             case name: TermName => TermRef.all(readType(), name)
             case (name: TermName, sig: Signature) => TermRef.withSig(readType(), name, sig)
           }
+        case THIS =>
+          ThisType.raw(readType().asInstanceOf[TypeRef])
         case SKOLEMtype =>
           SkolemType(readTypeRef())
         case NOTYPE =>
@@ -391,11 +390,9 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, roots: Set[
           case INSUPERCALL => addFlag(InSuperCall)
           case PRIVATEqualified => 
             readByte()
-            readEnd()
             privateWithin = readType().typeSymbol
           case PROTECTEDqualified =>
             addFlag(Protected)
-            readEnd()
             privateWithin = readType().typeSymbol
           case ANNOTATION =>
             readByte()
@@ -549,7 +546,6 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, roots: Set[
       val self = 
         if (nextByte == SELFDEF) {
           readByte()
-          readEnd()
           untpd.ValDef(readName(), readTpt(), EmptyTree).withType(NoType)
         }
         else EmptyValDef
@@ -622,6 +618,8 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, roots: Set[
             case name: Name => readQual(name).select(name)
             case (name: Name, sig: Signature) => readQual(name).selectWithSig(name, sig)
           }
+        case NEW =>
+          New(readTpt())
         case EMPTYTREE =>
           EmptyTree
         case _ =>
@@ -648,8 +646,6 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, roots: Set[
               tpd.Apply(fn, until(end)(readArg()))
             case TYPEAPPLY =>
               tpd.TypeApply(readTerm(), until(end)(readTpt()))
-            case NEW =>
-              New(readTpt())
             case PAIR =>
               Pair(readTerm(), readTerm())
             case TYPED =>
@@ -694,9 +690,8 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table, roots: Set[
             case UNAPPLY =>
               val fn = readTerm()
               val implicitArgs = 
-                collectWhile(nextByte == IMPLICITARG) {
+                collectWhile(nextByte == IMPLICITarg) {
                   readByte()
-                  readEnd()
                   readTerm()
                 }
               val patType = readType()