Summary printing

Added general way to produce summaries when shwowing trees or types.
Summaries have limited, configrable recusion depth.
fix showSummary

Author: odersky

src/dotty/tools/dotc/config/Config.scala

@@ -27,4 +27,7 @@ object Config {
    *  Disadvantage: It might hide inconsistencies, so while debugging it's better to turn it off
    */
   final val newMatch = false
+
+  /** The recursion depth for showing a summarized string */
+  final val summarizeDepth = 2
 }

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

@@ -7,6 +7,7 @@ import Contexts.Context, Scopes.Scope, Denotations.Denotation, Annotations.Annot
 import StdNames.nme
 import ast.Trees._, ast.untpd
 import java.lang.Integer.toOctalString
+import config.Config.summarizeDepth
 import scala.annotation.switch
 
 class PlainPrinter(_ctx: Context) extends Printer {
@@ -15,20 +16,21 @@ class PlainPrinter(_ctx: Context) extends Printer {
   protected def maxToTextRecursions = 100
 
   protected final def controlled(op: => Text): Text =
-    if (ctx.toTextRecursions < maxToTextRecursions)
+    if (ctx.toTextRecursions < maxToTextRecursions && ctx.toTextRecursions < maxSummarized)
       try {
         ctx.toTextRecursions += 1
         op
       } finally {
         ctx.toTextRecursions -= 1
       }
     else {
-      recursionLimitExceeded()
+      if (ctx.toTextRecursions >= maxToTextRecursions)
+        recursionLimitExceeded()
       "..."
     }
 
   protected def recursionLimitExceeded() = {
-    ctx.warning("Exceeded recursion depth attempting to print type.")
+    ctx.warning("Exceeded recursion depth attempting to print.")
     (new Throwable).printStackTrace
   }
 
@@ -393,6 +395,17 @@ class PlainPrinter(_ctx: Context) extends Printer {
     }
   }.close // todo: override in refined printer
 
+  private var maxSummarized = Int.MaxValue
+
+  def summarized[T](depth: Int)(op: => T): T = {
+    val saved = maxSummarized
+    maxSummarized = ctx.toTextRecursions + depth
+    try op
+    finally maxSummarized = depth
+  }
+
+  def summarized[T](op: => T): T = summarized(summarizeDepth)(op)
+
   def plain = this
 }
 

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

@@ -88,6 +88,11 @@ abstract class Printer {
   /** Textual representation of tree */
   def toText[T >: Untyped](tree: Tree[T]): Text
 
+  /** Perform string or text-producing operation `op` so that only a
+   *  summarized text with given recursion depth is shown
+   */
+  def summarized[T](depth: Int)(op: => T): T
+
   /** A plain printer without any embellishments */
   def plain: Printer
 }

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

@@ -127,7 +127,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
     super.toText(tp)
   }
 
-  override def toText[T >: Untyped](tree: Tree[T]): Text = {
+  override def toText[T >: Untyped](tree: Tree[T]): Text = controlled {
 
     def optDotPrefix(name: Name) = optText(name)(_ ~ ".")
 
@@ -242,7 +242,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
       case SeqLiteral(elems) =>
         "[" ~ toTextGlobal(elems, ",") ~ "]"
       case tpt: untpd.DerivedTypeTree =>
-        "<derived typetree watching " ~ toText(tpt.watched) ~ ">"
+        "<derived typetree watching " ~ summarized(toText(tpt.watched)) ~ ">"
       case TypeTree(orig) =>
         if (tree.hasType) toText(tree.typeOpt) else toText(orig)
       case SingletonTypeTree(ref) =>

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

@@ -4,6 +4,7 @@ package printing
 import core._
 
 import Contexts._, Texts._, Decorators._
+import config.Config.summarizeDepth
 
 trait Showable extends Any {
 
@@ -20,4 +21,13 @@ trait Showable extends Any {
 
   /** The string representation of this showable element. */
   def show(implicit ctx: Context): String = toText(ctx.printer).show
-}
+
+  /** The summarized string representation of this showable element.
+   *  Recursion depth is limited to some smallish value. Default is
+   *  Config.summarizeDepth.
+   */
+  def showSummary(depth: Int)(implicit ctx: Context): String =
+    ctx.printer.summarized(depth)(show)
+
+  def showSummary(implicit ctx: Context): String = showSummary(summarizeDepth)
+}