How can an implicit be unimported from the Scala repl? - scala

Question

Is it possible to unimport an implicit from the repl?
Say I do something like this,
scala> import scala.math.BigInt._
import scala.math.BigInt._
scala> :implicits
/* 2 implicit members imported from scala.math.BigInt */
/* 2 defined in scala.math.BigInt */
implicit def int2bigInt(i: Int): scala.math.BigInt
implicit def long2bigInt(l: Long): scala.math.BigInt
And then decide that it was all a big mistake. How can I remove those implicits from the current scope?
My current technique is aborting the REPL and then starting a new one, I'm keen to avoid repeating it.

Answer 1

You can hide an implicit by creating another implicit with the same name. Fortunately (for this case, anyway), rather than having an overloaded implicit, the new one displaces the old one:
scala> import language.implicitConversions
import language.implicitConversions
scala> def needsBoolean(b: Boolean) = !b
needsBoolean: (b: Boolean)Boolean
scala> implicit def int2bool(i: Int) = i==0
int2bool: (i: Int)Boolean
scala> val dangerous = needsBoolean(0)
dangerous: Boolean = false
scala> trait ThatWasABadIdea
defined trait ThatWasABadIdea
scala> implicit def int2bool(ack: ThatWasABadIdea) = ack
int2bool: (ack: ThatWasABadIdea)ThatWasABadIdea
scala> val safe = needsBoolean(0)
<console>:14: error: type mismatch;
found : Int(0)
required: Boolean
val safe = needsBoolean(0)