Scala example source code file (Adaptations.scala)

This example Scala source code file (Adaptations.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

adaptation, adapting, analyzer, boolean, compiler, list, nil, no, nsc, objectclass, string, tree, typer

The Adaptations.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author  Paul Phillips
 */

package scala.tools.nsc
package typechecker

/** This trait provides logic for assessing the validity of argument
 *  adaptations, such as tupling, unit-insertion, widening, etc.  Such
 *  logic is spread around the compiler, without much ability on the
 *  part of the user to tighten the potentially dangerous bits.
 *
 *  TODO: unifying/consolidating said logic under consistent management.
 *
 *  @author  Paul Phillips
 */
trait Adaptations {
  self: Analyzer =>

  import global._
  import definitions._

  trait Adaptation {
    self: Typer =>

    import runDefinitions._

    def checkValidAdaptation(t: Tree, args: List[Tree]): Boolean = {
      def applyArg = t match {
        case Apply(_, arg :: Nil) => arg
        case _                    => EmptyTree
      }
      def callString = (
        ( if (t.symbol.isConstructor) "new " else "" ) +
        ( t.symbol.owner.decodedName ) +
        ( if (t.symbol.isConstructor || t.symbol.name == nme.apply) "" else "." + t.symbol.decodedName )
      )
      def sigString = t.symbol.owner.decodedName + (
        if (t.symbol.isConstructor) t.symbol.signatureString
        else "." + t.symbol.decodedName + t.symbol.signatureString
      )
      def givenString = if (args.isEmpty) "<none>" else args.mkString(", ")
      def adaptedArgs = if (args.isEmpty) "(): Unit" else args.mkString("(", ", ", "): " + applyArg.tpe)

      def adaptWarningMessage(msg: String, showAdaptation: Boolean = true) = msg +
        "\n        signature: " + sigString +
        "\n  given arguments: " + givenString +
        (if (showAdaptation) "\n after adaptation: " + callString + "(" + adaptedArgs + ")" else "")

      // A one-argument method accepting Object (which may look like "Any"
      // at this point if the class is java defined) is a "leaky target" for
      // which we should be especially reluctant to insert () or auto-tuple.
      def isLeakyTarget = {
        val oneArgObject = t.symbol.paramss match {
          case (param :: Nil) :: Nil  => ObjectClass isSubClass param.tpe.typeSymbol
          case _                      => false
        }
        // Unfortunately various "universal" methods and the manner in which
        // they are used limits our ability to enforce anything sensible until
        // an opt-in compiler option is given.
        oneArgObject && !(
             isStringAddition(t.symbol)
          || isArrowAssoc(t.symbol)
          || t.symbol.name == nme.equals_
          || t.symbol.name == nme.EQ
          || t.symbol.name == nme.NE
        )
      }

      if (settings.noAdaptedArgs)
        context.warning(t.pos, adaptWarningMessage("No automatic adaptation here: use explicit parentheses."))
      else if (args.isEmpty) {
        if (settings.future)
          context.error(t.pos, adaptWarningMessage("Adaptation of argument list by inserting () has been removed.", showAdaptation = false))
        else {
          val msg = "Adaptation of argument list by inserting () has been deprecated: " + (
          if (isLeakyTarget) "leaky (Object-receiving) target makes this especially dangerous."
          else "this is unlikely to be what you want.")
          context.unit.deprecationWarning(t.pos, adaptWarningMessage(msg))
        }
      } else if (settings.warnAdaptedArgs)
        context.warning(t.pos, adaptWarningMessage(s"Adapting argument list by creating a ${args.size}-tuple: this may not be what you want."))

      !settings.noAdaptedArgs || !(args.isEmpty && settings.future)
    }
  }
}