Disabling implicit conversions around equality comparisons with Scalaz's Equal and Scalactic

gistfile1.scala

scala> import scalaz._
import scalaz._

scala> import Scalaz.{ToEqualOps => _, _}
import Scalaz.{ToEqualOps=>_, _}

scala> import equalitydemo.StrictScalazEquality._ // Import a "stricter" policy
import equalitydemo.StrictScalazEquality._

scala> 1L === 1 // Now implicit conversions aren't used to fix an quality comparison
<console>:17: error: types Long and Int do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.Constraint[Long,Int]
              1L === 1
                 ^

scala> 1 === 1L // And it is symmetric. Works in either arrangement.
<console>:17: error: types Int and Long do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.Constraint[Int,Long]
              1 === 1L
                ^

scala> 1L === 1.toLong // To get it to work, you need to explicitly convert
res2: Boolean = true

scala> 1.toLong === 1L
res3: Boolean = true

scala> 1 === ()
<console>:17: error: types Int and Unit do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.Constraint[Int,Unit]
              1 === ()
                ^

scala> () === 1
<console>:17: error: types Unit and Int do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.Constraint[Unit,Int]
              () === 1
                 ^

scala> 

scala> case class Box[T](o: T)
defined class Box

scala> 

scala> Box(1) === Box(1)
<console>:19: error: types Box[Int] and Box[Int] do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.Constraint[Box[Int],Box[Int]]
              Box(1) === Box(1)
                     ^

scala> 

scala> implicit def boxEqual[T] =
     |   new Equal[Box[T]] {
     |     def equal(a: Box[T], b: Box[T]): Boolean = a == b
     |   }
boxEqual: [T]=> scalaz.Equal[Box[T]]

scala> 

scala> Box(1) === Box(1)
res7: Boolean = true

scala> 

scala> Box(1) === 1
<console>:20: error: types Box[Int] and Int do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.Constraint[Box[Int],Int]
              Box(1) === 1
                     ^

scala> 1 === Box(1)
<console>:20: error: types Int and Box[Int] do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.Constraint[Int,Box[Int]]
              1 === Box(1)
                ^

scala> 

scala> import scala.language.implicitConversions
import scala.language.implicitConversions

scala> implicit def widenIntToBox(i: Int): Box[Int] = Box(i)
widenIntToBox: (i: Int)Box[Int]

scala> 

scala> Box(1) === 1 // Same here. Implicit conversion isn't used
<console>:22: error: types Box[Int] and Int do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.Constraint[Box[Int],Int]
              Box(1) === 1
                     ^

scala> 1 === Box(1) // In either direction.
<console>:22: error: types Int and Box[Int] do not adhere to the type constraint selected for the === and !== operators; the missing implicit parameter is of type org.scalactic.Constraint[Int,Box[Int]]
              1 === Box(1)
                ^

scala> 

scala> Box(1) === widenIntToBox(1) // You need to explicitly convert
res12: Boolean = true

scala> widenIntToBox(1) === Box(1)
res13: Boolean = true

scala> 

// Here's the code I pasted into the REPL:
import scalaz._
import Scalaz.{ToEqualOps => _, _}
import equalitydemo.StrictScalazEquality._
1L === 1
1 === 1L
1L === 1.toLong
1.toLong === 1L
1 === ()
() === 1

case class Box[T](o: T)

Box(1) === Box(1)

implicit def boxEqual[T] =
  new Equal[Box[T]] {
    def equal(a: Box[T], b: Box[T]): Boolean = a == b
  }

Box(1) === Box(1)

Box(1) === 1
1 === Box(1)

import scala.language.implicitConversions
implicit def widenIntToBox(i: Int): Box[Int] = Box(i)

Box(1) === 1
1 === Box(1)

Box(1) === widenIntToBox(1)
widenIntToBox(1) === Box(1)