org.scalactic.ConversionCheckedTripleEquals.scala Maven / Gradle / Ivy
/*
* 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.scalactic
import TripleEqualsSupport._
/**
* Trait ConversionCheckedTripleEquals has been deprecated and will be removed in a future version of Scalactic. Please use TypeCheckedTripleEquals with a type annotation instead.
*
*
* Trait ConversionCheckedTripleEquals has been deprecated because code that uses it can break if you
* change the equality policy to TripleEquals. For example, because JavaConversions provides
* an implicit conversion between java.util.Set and scala.collection.mutable.Set,
* an equality comparison under ConversionCheckedTripleEquals can yield true:
*
*
*
* scala> import collection.JavaConversions._
* import collection.JavaConversions._
*
* scala> import collection.mutable
* import collection.mutable
*
* scala> import ConversionCheckedTripleEquals._
* import ConversionCheckedTripleEquals._
*
* scala> mutable.Set.empty[String] === new java.util.HashSet[String]
* res0: Boolean = true
*
*
*
* If code written under ConversionCheckedTripleEquals is left unchanged, but the policy
* is changed to TripleEquals, the equality comparison will now yield false:
*
*
*
* scala> import TripleEquals._
* import TripleEquals._
*
* scala> mutable.Set.empty[String] === (new java.util.HashSet[String])
* res1: Boolean = false
*
*
*
* The above change from true to false happens without any warning
* or complaint from the compiler. Thus it is quite error prone. A better way to achieve equality
* comparisons after an implicit conversion is to do so explicitly, by forcing
* the implicit conversion via a type annotation (following an expression with a colon and
* the desired type). Here's an example:
*
*
*
* scala> mutable.Set.empty[String] === (new java.util.HashSet[String]: mutable.Set[String])
* res3: Boolean = true
*
*
*
* To get rid of the deprecation warning, you can use TypeCheckedTripleEquals instead of
* ConversionCheckedTripleEquals, and add explicit type annotations where needed:
*
*
*
* scala> import TypeCheckedTripleEquals._
* import TypeCheckedTripleEquals._
*
* scala> mutable.Set.empty[String] === new java.util.HashSet[String]
* <console>:27: error: types scala.collection.mutable.Set[String] and java.util.HashSet[String] do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.CanEqual[scala.collection.mutable.Set[String],java.util.HashSet[String]]
* mutable.Set.empty[String] === (new java.util.HashSet[String])
* ^
*
* scala> mutable.Set.empty[String] === (new java.util.HashSet[String]: mutable.Set[String])
* res4: Boolean = true
*
*
* @author Bill Venners
*/
@deprecated("ConversionCheckedTripleEquals has been deprecated and will be removed in a future version of Scalactic. Please use TypeCheckedTripleEquals with a type annotation instead")
trait ConversionCheckedTripleEquals extends LowPriorityConversionCheckedConstraint {
import scala.language.implicitConversions
// Inherit the Scaladoc for these methods
override def convertToEqualizer[T](left: T): Equalizer[T] = new Equalizer(left)
implicit override def convertToCheckingEqualizer[T](left: T): CheckingEqualizer[T] = new CheckingEqualizer(left)
override def unconstrainedEquality[A, B](implicit equalityOfA: Equality[A]): A CanEqual B = new EqualityConstraint[A, B](equalityOfA)
override def lowPriorityTypeCheckedConstraint[A, B](implicit equivalenceOfB: Equivalence[B], ev: A <:< B): A CanEqual B = new AToBEquivalenceConstraint[A, B](equivalenceOfB, ev)
override def convertEquivalenceToAToBConstraint[A, B](equivalenceOfB: Equivalence[B])(implicit ev: A <:< B): A CanEqual B = new AToBEquivalenceConstraint[A, B](equivalenceOfB, ev)
override def typeCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], ev: B <:< A): A CanEqual B = new BToAEquivalenceConstraint[A, B](equivalenceOfA, ev)
override def convertEquivalenceToBToAConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: B <:< A): A CanEqual B = new BToAEquivalenceConstraint[A, B](equivalenceOfA, ev)
implicit override def conversionCheckedConstraint[A, B](implicit equivalenceOfA: Equivalence[A], cnv: B => A): A CanEqual B = new BToAEquivalenceConstraint[A, B](equivalenceOfA, cnv)
implicit override def convertEquivalenceToBToAConversionConstraint[A, B](equivalenceOfA: Equivalence[A])(implicit ev: B => A): A CanEqual B = new BToAEquivalenceConstraint[A, B](equivalenceOfA, ev)
}
/**
* Object ConversionCheckedTripleEquals has been deprecated and will be removed in a future version of Scalactic. Please use TypeCheckedTripleEquals with a type annotation instead.
*
*
* For more information and examples, please see the documentation for the ConversionCheckedTripleEqals companion trait.
*
*/
@deprecated("ConversionCheckedTripleEquals has been deprecated and will be removed in a future version of Scalactic. Please use TypeCheckedTripleEquals with a type annotation instead")
object ConversionCheckedTripleEquals extends ConversionCheckedTripleEquals