如何在 REPL 中使用 :phase power 命令？

Question

Scala REPL 的

Power mode 启用 :phase 命令：

:phase <phase>           set the implicit phase for power commands

我似乎找不到有关如何使用此命令的文档。例如，假设我设置 parser compiler phase

scala> :phase parser
Active phase is now: Parser

什么power命令受到了影响？我如何调用这些受影响的电源命令？它与 :settings -Xprint:parser 有何不同？

Answer 1

该命令会导致您的代码被计算 enteringPhase，这是使用 intp.setExecutionWrapper 完成的。你可以用 -Dscala.repl.debug.

见证包装

它包装了REPL的"print"：

lazy val $print: _root_.java.lang.String = $line4.$read.$iw.$iw.$r.phased.atCurrent {

phased 对象只是调整对 enteringPhase 的调用。

这是一个示例，您可以在稍后阶段看到已擦除的类型：

scala> global.rootMirror.staticClass("scala.Option").typeSignature
res0: $r.global.Type =
[+A <: <?>]AnyRef
        with IterableOnce[A]
        with Product
        with Serializable {
  def <init>(): Option[A]
  final def isEmpty: Boolean
  final def isDefined: Boolean
  final override def knownSize: Int
  def get: A
  final def getOrElse[B >: A](default: => B): B
  final def orNull[A1 >: A](implicit ev: Null <:< A1): A1
  final def map[B](f: A => B): Option[B]
  final def fold[B](ifEmpty: => B)(f: A => B): B
  final def flatMap[B](f: A => Option[B]): Option[B]
  def flatten[B](implicit ev: A <:< Option[B]): Option[B]
  final def filter(p: A => Boolean): Option[A]
  final def filterNot(p: A => Boolean): Option[A]
  final def nonEmpty: Boolean
  final def withFilter(p: A => Boolean): Option.this.WithFilter
  class WithFilter extends AnyRef
  final def...

scala> global.rootMirror.staticClass("scala.Option").typeSignature.getClass
res1: Class[_ <: $r.global.Type] = class scala.reflect.internal.Types$PolyType

scala> :phase cleanup
Active phase is now: Cleanup

scala> global.rootMirror.staticClass("scala.Option").typeSignature.getClass
res2: Class[_ <: $r.global.Type] = class scala.reflect.internal.Types$ClassInfoType

scala> global.rootMirror.staticClass("scala.Option").typeSignature
res3: $r.global.Type =
Object
        with scala.collection.IterableOnce
        with Product
        with java.io.Serializable {
  def <init>(): Option
  final def isEmpty(): Boolean
  final def isDefined(): Boolean
  final override def knownSize(): Int
  def get(): Object
[snip]

REPL中的:type命令不受影响，因为它调用了exitingTyper.

如何在 REPL 中使用 :phase power 命令？

How to use :phase power command in REPL?

scala

read-eval-print-loop