Enabling implicit conversions

Consider these two packages:

package foo
given StringIntConversion: Conversion[String, Int] = _.toInt
package bar
import foo.StringIntConversion
val n: Int = "42"

The -feature option of the compiler produces a warning in both packages foo and bar. I would expect a warning in foo but not in bar.

The compiler also adds: See the Scala docs for value scala.language.implicitConversions for a discussion. The scaladoc (API) is silent, but an older documentation page on implicit conversions states:

To turn off the warnings take either of these actions:

- Import scala.language.implicitConversions into the scope of the implicit conversion definition
- Invoke the compiler with -language:implicitConversions

No warning is emitted when the conversion is applied by the compiler.

That doesn’t seem consistent with the observed behavior.

I believe this is something that changed in Scala 3 to make implicit conversions more annoying to use. But I can’t immediately find documentation on that change.