More user friendly printing of prototypes

FunProto and PolyProto now print without exposing internal names.

Author: odersky

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -232,11 +232,11 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
           case dummyTreeOfType(tp) :: Nil if !(tp isRef defn.NullClass) => "null: " ~ toText(tp)
           case _ => toTextGlobal(args, ", ")
         }
-        return "FunProto(" ~ (Str("given ") provided tp.isContextual) ~ argsText ~ "):" ~ toText(resultType)
+        return "[applied to " ~ (Str("given ") provided tp.isContextual) ~ "(" ~ argsText ~ ") returning " ~ toText(resultType) ~ "]"
       case IgnoredProto(ignored) =>
         return "?" ~ (("(ignored: " ~ toText(ignored) ~ ")") provided ctx.settings.verbose.value)
       case tp @ PolyProto(targs, resType) =>
-        return "PolyProto(" ~ toTextGlobal(targs, ", ") ~ "): " ~ toText(resType)
+        return "[applied to [" ~ toTextGlobal(targs, ", ") ~ "] returning " ~ toText(resType)
       case _ =>
     }
     super.toText(tp)