Unpickle Imports

Was missing before. Needed a tweak in PlainPrinter for printing
import symbol references (their denotation is not current after pickling, so
they would have printed differently after and before pickling).

Author: odersky

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

@@ -657,10 +657,10 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table) {
     }
 
     def readIndexedStat(exprOwner: Symbol)(implicit ctx: Context): Tree = nextByte match {
-      case TYPEDEF | VALDEF | DEFDEF | IMPORT =>
+      case TYPEDEF | VALDEF | DEFDEF =>
         readIndexedDef()
       case IMPORT =>
-        ???
+        readImport()
       case PACKAGE =>
         val start = currentAddr
         processPackage { (pid, end) => implicit ctx =>
@@ -669,6 +669,24 @@ class TreeUnpickler(reader: TastyReader, tastyName: TastyName.Table) {
       case _ =>
         readTerm()(ctx.withOwner(exprOwner))
     }
+    
+    def readImport()(implicit ctx: Context): Tree = {
+      readByte()
+      readEnd()
+      val expr = readTerm()
+      def readSelectors(): List[untpd.Tree] = nextByte match {
+        case RENAMED =>
+          readByte()
+          readEnd()
+          untpd.Pair(untpd.Ident(readName()), untpd.Ident(readName())) :: readSelectors()
+        case IMPORTED =>
+          readByte()
+          untpd.Ident(readName()) :: readSelectors()
+        case _ =>
+          Nil
+      }
+      Import(expr, readSelectors())
+    }
 
     def readIndexedStats(exprOwner: Symbol, end: Addr)(implicit ctx: Context): List[Tree] =
       until(end)(readIndexedStat(exprOwner))

src/dotty/tools/dotc/printing/PlainPrinter.scala

@@ -109,7 +109,7 @@ class PlainPrinter(_ctx: Context) extends Printer {
     homogenize(tp) match {
       case tp: TypeType =>
         toTextRHS(tp)
-      case tp: TermRef if !tp.denotationIsCurrent || tp.symbol.is(Module) =>
+      case tp: TermRef if !tp.denotationIsCurrent || tp.symbol.is(Module) || tp.symbol.name.isImportName =>
         toTextRef(tp) ~ ".type"
       case tp: TermRef if tp.denot.isOverloaded =>
         "<overloaded " ~ toTextRef(tp) ~ ">"

tests/new/test.scala

@@ -0,0 +1,12 @@
+trait T {
+  object O
+}
+
+class C extends T
+
+object Test {
+
+  val c = new C
+  c.O
+
+}