Drop environment from pickled closures.

It is always empty anyway. Side benefit: We can get rid of NOTYPE, too.

Author: odersky

src/dotty/tools/dotc/core/pickling/TreePickler.scala

@@ -248,8 +248,6 @@ class TreePickler(pickler: TastyPickler) {
         assert(pickleParamType(tpe), s"orphan method parameter: $tpe")
       case tpe: LazyRef =>
         pickleType(tpe.ref)
-      case NoType =>
-        writeByte(NOTYPE)
     }} catch {
       case ex: AssertionError => 
         println(i"error while pickling type $tpe")
@@ -353,8 +351,12 @@ class TreePickler(pickler: TastyPickler) {
         writeByte(IF)
         withLength{ pickleTree(cond); pickleTree(thenp); pickleTree(elsep) }
       case Closure(env, meth, tpt) => 
-        writeByte(CLOSURE)
-        withLength{ pickleTree(meth); pickleTpt(tpt); env.foreach(pickleTree) }
+        writeByte(LAMBDA)
+        assert(env.isEmpty)
+        withLength{ 
+          pickleTree(meth)
+          if (tpt.tpe.exists) pickleTpt(tpt) 
+        }
       case Match(selector, cases) =>
         writeByte(MATCH)
         withLength { pickleTree(selector); cases.foreach(pickleTree) }

src/dotty/tools/dotc/core/pickling/TreeUnpickler.scala

@@ -267,8 +267,6 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table) {
           ThisType.raw(readType().asInstanceOf[TypeRef])
         case SKOLEMtype =>
           SkolemType(readTypeRef())
-        case NOTYPE =>
-          NoType
         case SHARED =>
           val ref = readAddr()
           typeAtAddr.getOrElseUpdate(ref, forkAt(ref).readType())
@@ -747,10 +745,10 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table) {
               Block(stats, expr)
             case IF =>
               If(readTerm(), readTerm(), readTerm())
-            case CLOSURE =>
+            case LAMBDA =>
               val meth = readTerm()
-              val tpt = readTpt()
-              Closure(until(end)(readTerm()), meth, tpt)
+              val tpt = ifBefore(end)(readTpt(), EmptyTree)
+              Closure(Nil, meth, tpt)
             case MATCH =>
               Match(readTerm(), readCases(end))
             case RETURN =>