Extends the functionality of scala.annotation.implicitNotFound so that implicit-not-found error message
is itself resolved using implicit search. This mechanism is used by Implicits.infer[T]:T* and macro engines
that use it.
Example: we have a wrapper class Box[T] and we want a custom error message when GenCodec[Box[T]] for some type
T is not found:
trait Box[T]
object Box {
implicitdef boxCodec[T: GenCodec]: GenCodec[Box[T]] = ...
@implicitNotFound("GenCodec for Box[$${T}] not found. This is most likely caused by lack of GenCodec[$${T}]")
implicitdef boxCodecNotFound[T]: ImplicitNotFound[GenCodec[Box[T]]] = ImplicitNotFound()
}
It is also possible to compose error message for one type from error messages for other types. The example
above could reuse the implicit-not-found message for GenCodec[T] when building the message for GenCodec[Box[T]]:
@implicitNotFound("GenCodec for Box[$${T}] not found, probably because: #{forUnboxed}")
implicitdef boxCodecNotFound[T](
implicit forUnboxed: ImplicitNotFound[GenCodec[T]]
): ImplicitNotFound[GenCodec[Box[T]]] = ImplicitNotFound()
Extends the functionality of scala.annotation.implicitNotFound so that implicit-not-found error message is itself resolved using implicit search. This mechanism is used by Implicits.infer[T]:T* and macro engines that use it.
Example: we have a wrapper class
Box[T]and we want a custom error message whenGenCodec[Box[T]]for some typeTis not found:It is also possible to compose error message for one type from error messages for other types. The example above could reuse the implicit-not-found message for
GenCodec[T]when building the message forGenCodec[Box[T]]: