dotty.tools.dotc.transform.TransformWildcards.scala Maven / Gradle / Ivy

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package dotty.tools.dotc
package transform

import MegaPhase.*
import core.DenotTransformers.*
import core.Contexts.*
import ast.tpd

/** This phase transforms wildcards in valdefs with their default value.
  *  In particular for every valdef that is declared:
  *    `val x : T = _` to `val x : T = `
  *
  */
class TransformWildcards extends MiniPhase with IdentityDenotTransformer {
  import tpd.*

  override def phaseName: String = TransformWildcards.name

  override def description: String = TransformWildcards.description

  override def checkPostCondition(tree: Tree)(using Context): Unit =
    tree match {
      case vDef: ValDef => assert(!tpd.isWildcardArg(vDef.rhs))
      case _ =>
    }

  override def transformValDef(tree: ValDef)(using Context): Tree =
    if (ctx.owner.isClass) tree
    else cpy.ValDef(tree)(rhs = tree.rhs.wildcardToDefault)
}

object TransformWildcards:
  val name: String = "transformWildcards"
  val description: String = "replace wildcards with default values"