Properly display value of value class in repl (#15545)

* fix repl to properly display value of value class after it's creation

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

@@ -37,7 +37,7 @@ class ReplPrinter(_ctx: Context) extends RefinedPrinter(_ctx) {
       if (sym.is(Method)) {
         sym.info match {
           case tp: ExprType => ":" ~~ toText(tp.resType)
-          case _ => toText(sym.info)
+          case info => toText(info)
         }
       }
       else if (sym.isType && sym.info.isTypeAlias) toText(sym.info)

compiler/src/dotty/tools/repl/Rendering.scala

@@ -14,6 +14,7 @@ import dotc.core.Symbols.{Symbol, defn}
 import dotc.core.StdNames.{nme, str}
 import dotc.printing.ReplPrinter
 import dotc.reporting.Diagnostic
+import dotc.transform.ValueClasses
 
 /** This rendering object uses `ClassLoader`s to accomplish crossing the 4th
  *  wall (i.e. fetching back values from the compiled class files put into a
@@ -23,7 +24,7 @@ import dotc.reporting.Diagnostic
  *       `ReplDriver#resetToInitial` is called, the accompanying instance of
  *       `Rendering` is no longer valid.
  */
-private[repl] class Rendering(parentClassLoader: Option[ClassLoader] = None) {
+private[repl] class Rendering(parentClassLoader: Option[ClassLoader] = None):
 
   import Rendering._
 
@@ -80,43 +81,53 @@ private[repl] class Rendering(parentClassLoader: Option[ClassLoader] = None) {
    * then this bug will surface, so perhaps better not?
    * https://github.com/scala/bug/issues/12337
    */
-  private[repl] def truncate(str: String): String = {
+  private[repl] def truncate(str: String): String =
     val showTruncated = " ... large output truncated, print value to show all"
     val ncp = str.codePointCount(0, str.length) // to not cut inside code point
     if ncp <= MaxStringElements then str
     else str.substring(0, str.offsetByCodePoints(0, MaxStringElements - 1)) + showTruncated
-  }
 
   /** Return a String representation of a value we got from `classLoader()`. */
-  private[repl] def replStringOf(value: Object)(using Context): String = {
+  private[repl] def replStringOf(value: Object)(using Context): String =
     assert(myReplStringOf != null,
       "replStringOf should only be called on values creating using `classLoader()`, but `classLoader()` has not been called so far")
     val res = myReplStringOf(value)
     if res == null then "null // non-null reference has null-valued toString" else truncate(res)
-  }
 
   /** Load the value of the symbol using reflection.
    *
    *  Calling this method evaluates the expression using reflection
    */
-  private def valueOf(sym: Symbol)(using Context): Option[String] = {
+  private def valueOf(sym: Symbol)(using Context): Option[String] =
     val objectName = sym.owner.fullName.encode.toString.stripSuffix("$")
     val resObj: Class[?] = Class.forName(objectName, true, classLoader())
-    val value =
-      resObj
-        .getDeclaredMethods.find(_.getName == sym.name.encode.toString)
-        .map(_.invoke(null))
-    val string = value.map(replStringOf(_))
+    val symValue = resObj
+      .getDeclaredMethods.find(_.getName == sym.name.encode.toString)
+      .flatMap(result => rewrapValueClass(sym.info.classSymbol, result.invoke(null)))
+    val valueString = symValue.map(replStringOf)
+
     if (!sym.is(Flags.Method) && sym.info == defn.UnitType)
       None
     else
-      string.map { s =>
+      valueString.map { s =>
         if (s.startsWith(REPL_WRAPPER_NAME_PREFIX))
           s.drop(REPL_WRAPPER_NAME_PREFIX.length).dropWhile(c => c.isDigit || c == '$')
         else
           s
       }
-  }
+
+  /** Rewrap value class to their Wrapper class
+   *
+   * @param sym Value Class symbol
+   * @param value underlying value
+   */
+  private def rewrapValueClass(sym: Symbol, value: Object)(using Context): Option[Object] =
+    if ValueClasses.isDerivedValueClass(sym) then
+      val valueClassName = sym.flatName.encode.toString
+      val valueClass = Class.forName(valueClassName, true, classLoader())
+      valueClass.getConstructors.headOption.map(_.newInstance(value))
+    else
+      Some(value)
 
   def renderTypeDef(d: Denotation)(using Context): Diagnostic =
     infoDiagnostic("// defined " ++ d.symbol.showUser, d)
@@ -171,9 +182,8 @@ private[repl] class Rendering(parentClassLoader: Option[ClassLoader] = None) {
   private def infoDiagnostic(msg: String, d: Denotation)(using Context): Diagnostic =
     new Diagnostic.Info(msg, d.symbol.sourcePos)
 
-}
 
-object Rendering {
+object Rendering:
   final val REPL_WRAPPER_NAME_PREFIX = str.REPL_SESSION_LINE
 
   extension (s: Symbol)
@@ -182,5 +192,3 @@ object Rendering {
       val text = printer.dclText(s)
       text.mkString(ctx.settings.pageWidth.value, ctx.settings.printLines.value)
     }
-
-}

compiler/test-resources/repl/i15493

@@ -0,0 +1,144 @@
+scala> class NInt(val x: Int) extends AnyVal
+// defined class NInt
+
+scala> NInt(23)
+val res0: NInt = NInt@17
+
+scala> res0.toString
+val res1: String = NInt@17
+
+scala> 23
+val res2: Int = 23
+
+scala> class NBoolean(val x: Boolean) extends AnyVal
+// defined class NBoolean
+
+scala> NBoolean(true)
+val res3: NBoolean = NBoolean@4cf
+
+scala> res3.toString
+val res4: String = NBoolean@4cf
+
+scala> true
+val res5: Boolean = true
+
+scala> class NByte(val x: Byte) extends AnyVal
+// defined class NByte
+
+scala> NByte(1)
+val res6: NByte = NByte@1
+
+scala> res6.toString
+val res7: String = NByte@1
+
+scala> val res8: Byte = 1
+val res8: Byte = 1
+
+scala> class NShort(val x: Short) extends AnyVal
+// defined class NShort
+
+scala> NShort(1)
+val res9: NShort = NShort@1
+
+scala> res9.toString
+val res10: String = NShort@1
+
+scala> val res11: Short = 1
+val res11: Short = 1
+
+scala> class NLong(val x: Long) extends AnyVal
+// defined class NLong
+
+scala> NLong(1)
+val res12: NLong = NLong@1
+
+scala> res12.toString
+val res13: String = NLong@1
+
+scala> 1L
+val res14: Long = 1
+
+scala> class NFloat(val x: Float) extends AnyVal
+// defined class NFloat
+
+scala> NFloat(1L)
+val res15: NFloat = NFloat@3f800000
+
+scala> res15.toString
+val res16: String = NFloat@3f800000
+
+scala> 1.0F
+val res17: Float = 1.0
+
+scala> class NDouble(val x: Double) extends AnyVal
+// defined class NDouble
+
+scala> NDouble(1D)
+val res18: NDouble = NDouble@3ff00000
+
+scala> res18.toString
+val res19: String = NDouble@3ff00000
+
+scala> 1.0D
+val res20: Double = 1.0
+
+scala> class NChar(val x: Char) extends AnyVal
+// defined class NChar
+
+scala> NChar('a')
+val res21: NChar = NChar@61
+
+scala> res21.toString
+val res22: String = NChar@61
+
+scala> 'a'
+val res23: Char = a
+
+scala> class NString(val x: String) extends AnyVal
+// defined class NString
+
+scala> NString("test")
+val res24: NString = NString@364492
+
+scala> res24.toString
+val res25: String = NString@364492
+
+scala> "test"
+val res26: String = test
+
+scala> class CustomToString(val x: Int) extends AnyVal { override def toString(): String = s"Test$x" }
+// defined class CustomToString
+
+scala> CustomToString(23)
+val res27: CustomToString = Test23
+
+scala> res27.toString
+val res28: String = Test23
+
+scala> class `<>`(x: Int) extends AnyVal
+// defined class <>
+
+scala> `<>`(23)
+val res29: <> = less$greater@17
+
+scala> res29.toString
+val res30: String = less$greater@17
+
+scala> class `🤪`(x: Int) extends AnyVal
+// defined class 🤪
+
+scala> `🤪`(23)
+val res31: 🤪 = uD83E$uDD2A@17
+
+scala> res31.toString
+val res32: String = uD83E$uDD2A@17
+
+scala> object Outer { class Foo(x: Int) extends AnyVal }
+// defined object Outer
+
+scala> Outer.Foo(23)
+val res33: Outer.Foo = Outer$Foo@17
+
+scala> res33.toString
+val res34: String = Outer$Foo@17
+