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/*
 * Copyright 2001-2013 Artima, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.scalautils

/**
 * Trait containing an implicit conversion that adds an asAny method to
 * anything, which returns the same object as type Any.
 *
 * 
 * The purpose of this method is to appease the type checker when necessary. For example,
 * in ScalaTest's matchers DSL the type passed to contain must be consistent
 * with the element type of the collection on which should is invoked. So
 * this type checks:
 * 
 *
 *  * Set(1, 2) should contain (2)
 * 
 * 
 * 
 * But this does not type check:
 * 
 * 
 *  * Set(1, 2) should contain ("2")
 * 
 * 
 * 
 * That is all well and good, but it turns out that this does also not type check, because the element type of
 * the collection (Any) is a supertype of the type passed to contain (String):
 * 
 * 
 *  * Set(1, "2") should contain ("2") // Does not compile
 * 
 * 
 * 
 * You can appease the type checker by casting the type of "2" to Any, a cast that
 * will always succeed. Using asAny makes this prettier:
 * 
 * 
 *  * Set(1, "2") should contain ("2".asAny)
 * 
 * 
 */
trait AsAny {

  /**
   * Wrapper class with an asAny method that returns the passed object
   * as type Any.
   *
   * @param o the object to return from asAny
   *
   * @author Bill Venners
   */
  class AsAnyWrapper(o: Any) {

    /**
     * Returns the object, o, passed to the constructor.
     *
     * @return the object passed to the constructor
     */
    def asAny: Any = o
  }

  /**
   * Implicit conversion that adds an asAny method to an object, which returns
   * the exact same object but as type Any.
   */
  implicit def convertToAsAnyWrapper(o: Any): AsAnyWrapper = new AsAnyWrapper(o)
}

/**
 * Companion object to trait AsAny that facilitates the importing of AsAny members as 
 * an alternative to mixing it in. One use case is to import AsAny members so you can use
 * them in the Scala interpreter:
 *
 *  * $ scala -classpath scalatest.jar
 * Welcome to Scala version 2.10.0
 * Type in expressions to have them evaluated.
 * Type :help for more information.
 *
 * scala> import org.scalatest._
 * import org.scalatest._
 *
 * scala> import Matchers._
 * import Matchers._
 *
 * scala> Set(1, "2") should contain (1)
 * :14: error: overloaded method value should with alternatives:
 * [R](inv: org.scalautils.TripleEqualsInvocation[R])(implicit constraint: org.scalautils.EqualityConstraint[scala.collection.immutable.Set[Any],R])Unit 
 * (notWord: org.scalatest.Matchers.NotWord)org.scalatest.Matchers.ResultOfNotWordForTraversable[Any,scala.collection.immutable.Set] 
 * (beWord: org.scalatest.Matchers.BeWord)org.scalatest.Matchers.ResultOfBeWordForAnyRef[scala.collection.GenTraversable[Any]] 
 * (containMatcher: org.scalatest.ContainMatcher[Any])Unit 
 * (containWord: org.scalatest.Matchers.ContainWord)org.scalatest.Matchers.ResultOfContainWordForTraversable[Any] 
 * (haveWord: org.scalatest.Matchers.HaveWord)org.scalatest.Matchers.ResultOfHaveWordForTraversable[Any] 
 * (rightMatcherGen1: org.scalatest.Matchers.MatcherGen1[scala.collection.immutable.Set[Any],org.scalautils.Equality])(implicit equality: org.scalautils.Equality[scala.collection.immutable.Set[Any]])Unit 
 * (rightMatcherX6: org.scalatest.matchers.Matcher[scala.collection.GenTraversable[Any]])Unit
 *cannot be applied to (org.scalatest.matchers.Matcher[scala.collection.GenTraversable[Int]])
 *             Set(1, "2") should contain (1)
 *                         ^
 *
 * scala> Set(1, "2") should contain (1.asAny)
 *
 * scala>
 * 
 */
object AsAny extends AsAny