Scala example source code file (Statics.scala)

This example Scala source code file (Statics.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

block, buffer, compiler, defdef, literal, nsc, option, statics, staticstransformer, template, termtree, transform

The Statics.scala Scala example source code

package scala.tools.nsc
package transform

import symtab._
import Flags._

import collection.mutable.Buffer

abstract class Statics extends Transform with ast.TreeDSL {
  import global._

  class StaticsTransformer extends Transformer {

    /** finds the static ctor DefDef tree within the template if it exists. */
    def findStaticCtor(template: Template): Option[Tree] =
      template.body find {
        case defdef @ DefDef(_, nme.CONSTRUCTOR, _, _, _, _) => defdef.symbol.hasStaticFlag
        case _ => false
      }

    /** changes the template for the class so that it contains a static constructor with symbol fields inits,
      * augments an existing static ctor if one already existed.
      */
    def addStaticInits(template: Template, newStaticInits: Buffer[Tree], localTyper: analyzer.Typer): Template = {
      if (newStaticInits.isEmpty)
        template
      else {
        val newCtor = findStaticCtor(template) match {
          // in case there already were static ctors - augment existing ones
          // currently, however, static ctors aren't being generated anywhere else
          case Some(ctor @ DefDef(_,_,_,_,_,_)) =>
            // modify existing static ctor
            deriveDefDef(ctor) {
              case block @ Block(stats, expr) =>
                // need to add inits to existing block
                treeCopy.Block(block, newStaticInits.toList ::: stats, expr)
              case term: TermTree =>
                // need to create a new block with inits and the old term
                treeCopy.Block(term, newStaticInits.toList, term)
            }
          case _ =>
            // create new static ctor
            val staticCtorSym  = currentClass.newStaticConstructor(template.pos)
            val rhs            = Block(newStaticInits.toList, Literal(Constant(())))

            localTyper.typedPos(template.pos)(DefDef(staticCtorSym, rhs))
        }
        deriveTemplate(template)(newCtor :: _)
      }
    }
  }
}