Refactor printing of capture sets

Author: odersky

compiler/src/dotty/tools/dotc/cc/CaptureSet.scala

@@ -320,7 +320,7 @@ sealed abstract class CaptureSet extends Showable:
     Annotation(CaptureAnnotation(this, boxed = false)(cls).tree)
 
   override def toText(printer: Printer): Text =
-    Str("{") ~ Text(elems.toList.map(printer.toTextCaptureRef), ", ") ~ Str("}") ~~ description
+    printer.toTextCaptureSet(this)
 
 object CaptureSet:
   type Refs = SimpleIdentitySet[CaptureRef]

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

@@ -156,8 +156,8 @@ class PlainPrinter(_ctx: Context) extends Printer {
     if printDebug && !cs.isConst then cs.toString
     else if ctx.settings.YccDebug.value then cs.show
     else if cs == CaptureSet.Fluid then "<fluid>"
-    else if !cs.isConst && cs.elems.isEmpty then Str("?") ~ nestingLevelStr
-    else "{" ~ Text(cs.elems.toList.map(toTextCaptureRef), ", ") ~ "}" ~ nestingLevelStr
+    else if !cs.isConst && cs.elems.isEmpty then Str("?") ~~ cs.description ~ nestingLevelStr
+    else "{" ~ Text(cs.elems.toList.map(toTextCaptureRef), ", ") ~ "}" ~~ cs.description ~ nestingLevelStr
 
   /** Print capturing type, overridden in RefinedPrinter to account for
    *  capturing function types.

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

@@ -10,6 +10,7 @@ import Types.{Type, SingletonType, LambdaParam, NamedType},
 import typer.Implicits.SearchResult
 import util.SourcePosition
 import typer.ImportInfo
+import cc.CaptureSet
 
 import scala.annotation.internal.sharable
 
@@ -106,6 +107,9 @@ abstract class Printer {
   /** Textual representation of a reference in a capture set */
   def toTextCaptureRef(tp: Type): Text
 
+  /** Textual representation of a reference in a capture set */
+  def toTextCaptureSet(cs: CaptureSet): Text
+
   /** Textual representation of symbol's declaration */
   def dclText(sym: Symbol): Text