Allow future defs when printing with i"...".

We saw a failure of accessing a denotation outside its defined interval, which got triggered
by i"...". This should never be the case. We should be more interested in what i"..." has to print.

Author: odersky

src/dotty/tools/dotc/core/Decorators.scala

@@ -7,6 +7,7 @@ import Contexts._, Names._, Phases._, printing.Texts._, printing.Printer, printi
 import util.Positions.Position, util.SourcePosition
 import collection.mutable.ListBuffer
 import dotty.tools.dotc.transform.TreeTransforms._
+import typer.Mode
 import scala.language.implicitConversions
 
 /** This object provides useful implicit decorators for types defined elsewhere */
@@ -172,7 +173,7 @@ object Decorators {
       def treatSingleArg(arg: Any) : Any =
         try
           arg match {
-            case arg: Showable => arg.show
+            case arg: Showable => arg.show(ctx.fresh.addMode(Mode.FutureDefsOK))
             case _ => arg
           }
         catch {