Scala example source code file (CommonOwners.scala)

This example Scala source code file (CommonOwners.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

commonownermap, list, nil, nosymbol, singletype, symbol, symboltable, type, typeref, typetraverserwithresult

The CommonOwners.scala Scala example source code

package scala
package reflect
package internal
package tpe

private[internal] trait CommonOwners {
  self: SymbolTable =>

  /** The most deeply nested owner that contains all the symbols
    *  of thistype or prefixless typerefs/singletype occurrences in given type.
    */
  protected[internal] def commonOwner(t: Type): Symbol = commonOwner(t :: Nil)

  /** The most deeply nested owner that contains all the symbols
    *  of thistype or prefixless typerefs/singletype occurrences in given list
    *  of types.
    */
  protected[internal] def commonOwner(tps: List[Type]): Symbol = {
    if (tps.isEmpty) NoSymbol
    else {
      commonOwnerMap.clear()
      tps foreach (commonOwnerMap traverse _)
      if (commonOwnerMap.result ne null) commonOwnerMap.result else NoSymbol
    }
  }

  protected def commonOwnerMap: CommonOwnerMap = commonOwnerMapObj

  protected class CommonOwnerMap extends TypeTraverserWithResult[Symbol] {
    var result: Symbol = _

    def clear() { result = null }

    private def register(sym: Symbol) {
      // First considered type is the trivial result.
      if ((result eq null) || (sym eq NoSymbol))
        result = sym
      else
        while ((result ne NoSymbol) && (result ne sym) && !(sym isNestedIn result))
          result = result.owner
    }
    def traverse(tp: Type) = tp.normalize match {
      case ThisType(sym)                => register(sym)
      case TypeRef(NoPrefix, sym, args) => register(sym.owner) ; args foreach traverse
      case SingleType(NoPrefix, sym)    => register(sym.owner)
      case _                            => mapOver(tp)
    }
  }

  private lazy val commonOwnerMapObj = new CommonOwnerMap
}