Fix #3608: Treat outer selections as separate Tasty tree

Tasty needs to know about outer selections as separate trees. So instead of
exposing a name for outer selects we expose a tree format. This allows us to
store the type of tree selection in the tree, which got lost before.

Also: Change format of NAMEDarg to no longer require a length.

Author: odersky

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

@@ -11,6 +11,10 @@ object NameTags extends TastyFormat.NameTags {
 
   final val TRAITSETTER = 6     // A Scala-2 trait setter, generated by AugmentScala2Traits
 
+  final val OUTERSELECT = 13    // A name `<num>_outer`, used by the inliner to indicate an
+                                // outer accessor that will be filled in by ExplicitOuter.
+                                // <num> indicates the number of hops needed to select the outer field.
+
   final val INITIALIZER = 24    // A mixin initializer method
 
   final val AVOIDCLASH = 25     // Adds a suffix to avoid a name clash;

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

@@ -37,12 +37,11 @@ Macro-format:
                   UNIQUE            Length separator_NameRef uniqid_Nat underlying_NameRef?
                   DEFAULTGETTER     Length underlying_NameRef index_Nat
                   VARIANT           Length underlying_NameRef variance_Nat      // 0: Contravariant, 1: Covariant
-                  OUTERSELECT       Length underlying_NameRef nhops_Nat
 
                   SUPERACCESSOR     Length underlying_NameRef
                   PROTECTEDACCESSOR Length underlying_NameRef
                   PROTECTEDSETTER   Length underlying_NameRef
-                  INITIALIZER       Length underlying_NameRef
+                  OBJECTCLASS       Length underlying_NameRef
 
                   SIGNED            Length original_NameRef resultSig_NameRef paramSig_NameRef*
 
@@ -81,9 +80,9 @@ Standard-Section: "ASTs" TopLevelStat*
                   SELECT                possiblySigned_NameRef qual_Term
                   QUALTHIS              typeIdent_Tree
                   NEW                   cls_Type
+                  NAMEDARG              paramName_NameRef arg_Term
                   SUPER          Length this_Term mixinTypeIdent_Tree?
                   TYPED          Length expr_Term ascription_Type
-                  NAMEDARG       Length paramName_NameRef arg_Term
                   ASSIGN         Length lhs_Term rhs_Term
                   BLOCK          Length expr_Term Stat*
                   INLINED        Length call_Term expr_Term Stat*
@@ -93,6 +92,7 @@ Standard-Section: "ASTs" TopLevelStat*
                   TRY            Length expr_Term CaseDef* finalizer_Term?
                   RETURN         Length meth_ASTRef expr_Term?
                   REPEATED       Length elem_Type elem_Term*
+                  SELECTouter    Length levels_Nat qual_Term underlying_Type
                   BIND           Length boundName_NameRef patType_Type pat_Term
                   ALTERNATIVE    Length alt_Term*
                   UNAPPLY        Length fun_Term ImplicitArg* pat_Type pat_Term*
@@ -248,10 +248,6 @@ object TastyFormat {
     final val VARIANT = 12           // A name `+<name>` o `-<name>` indicating
                                      // a co- or contra-variant parameter of a type lambda.
 
-    final val OUTERSELECT = 13       // A name `<num>_outer`, used by the inliner to indicate an
-                                     // outer accessor that will be filled in by ExplicitOuter.
-                                     // <num> indicates the number of hops needed to select the outer field.
-
     final val SUPERACCESSOR = 20     // The name of a super accessor `super$name` created by SuperAccesors.
 
     final val PROTECTEDACCESSOR = 21 // The name of a protected accessor `protected$<name>` created by SuperAccesors.
@@ -336,6 +332,7 @@ object TastyFormat {
   final val RECtype = 90
   final val TYPEALIAS = 91
   final val SINGLETONtpt = 92
+  final val NAMEDARG = 93
 
   // Cat. 4:    tag Nat AST
 
@@ -362,15 +359,15 @@ object TastyFormat {
   final val APPLY = 136
   final val TYPEAPPLY = 137
   final val TYPED = 138
-  final val NAMEDARG = 139
-  final val ASSIGN = 140
-  final val BLOCK = 141
-  final val IF = 142
-  final val LAMBDA = 143
-  final val MATCH = 144
-  final val RETURN = 145
-  final val TRY = 146
-  final val INLINED = 147
+  final val ASSIGN = 139
+  final val BLOCK = 140
+  final val IF = 141
+  final val LAMBDA = 142
+  final val MATCH = 143
+  final val RETURN = 144
+  final val TRY = 145
+  final val INLINED = 146
+  final val SELECTouter = 147
   final val REPEATED = 148
   final val BIND = 149
   final val ALTERNATIVE = 150
@@ -536,6 +533,7 @@ object TastyFormat {
     case MATCH => "MATCH"
     case RETURN => "RETURN"
     case INLINED => "INLINED"
+    case SELECTouter => "SELECTouter"
     case TRY => "TRY"
     case REPEATED => "REPEATED"
     case BIND => "BIND"

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

@@ -58,7 +58,7 @@ class TastyUnpickler(reader: TastyReader) {
         val originals = until(end)(readName())
         val original = if (originals.isEmpty) EmptyTermName else originals.head
         uniqueNameKindOfSeparator(separator)(original, num)
-      case DEFAULTGETTER | VARIANT | OUTERSELECT =>
+      case DEFAULTGETTER | VARIANT =>
         numberedNameKindOfTag(tag)(readName(), readNat())
       case SIGNED =>
         val original = readName()

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

@@ -342,10 +342,21 @@ class TreePickler(pickler: TastyPickler) {
             pickleTree(qual.withType(tref))
           }
         case Select(qual, name) =>
-          writeByte(if (name.isTypeName) SELECTtpt else SELECT)
-          val sig = tree.tpe.signature
-          pickleNameAndSig(name, sig)
-          pickleTree(qual)
+          name match {
+            case OuterSelectName(_, levels) =>
+              writeByte(SELECTouter)
+              withLength {
+                writeNat(levels)
+                pickleTree(qual)
+                val SkolemType(tp) = tree.tpe
+                pickleType(tp)
+              }
+            case _ =>
+              writeByte(if (name.isTypeName) SELECTtpt else SELECT)
+              val sig = tree.tpe.signature
+              pickleNameAndSig(name, sig)
+              pickleTree(qual)
+          }
         case Apply(fun, args) =>
           writeByte(APPLY)
           withLength {
@@ -382,7 +393,8 @@ class TreePickler(pickler: TastyPickler) {
           withLength { pickleTree(expr); pickleTpt(tpt) }
         case NamedArg(name, arg) =>
           writeByte(NAMEDARG)
-          withLength { pickleName(name); pickleTree(arg) }
+          pickleName(name)
+          pickleTree(arg)
         case Assign(lhs, rhs) =>
           writeByte(ASSIGN)
           withLength { pickleTree(lhs); pickleTree(rhs) }

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

@@ -909,6 +909,8 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
           SingletonTypeTree(readTerm())
         case BYNAMEtpt =>
           ByNameTypeTree(readTpt())
+        case NAMEDARG =>
+          NamedArg(readName(), readTerm())
         case _ =>
           readPathTerm()
       }
@@ -956,8 +958,6 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
                 case expr => expr
               }
               Typed(expr1, tpt)
-            case NAMEDARG =>
-              NamedArg(readName(), readTerm())
             case ASSIGN =>
               Assign(readTerm(), readTerm())
             case BLOCK =>
@@ -979,6 +979,9 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
               Return(expr, Ident(from.termRef))
             case TRY =>
               Try(readTerm(), readCases(end), ifBefore(end)(readTerm(), EmptyTree))
+            case SELECTouter =>
+              val levels = readNat()
+              readTerm().outerSelect(levels, SkolemType(readType()))
             case REPEATED =>
               val elemtpt = readTpt()
               SeqLiteral(until(end)(readTerm()), elemtpt)

tests/pickling/i3608.scala

@@ -0,0 +1,10 @@
+class A {
+  class Foo {
+    inline def inlineMeth: Unit = new Bar
+  }
+  class Bar
+}
+
+class B extends A {
+  (new Foo).inlineMeth
+}