Scalac does not seem to support JSR 308

[scabug]

JSR 308 brought annotations on type parameters such as

class SomeBean {
     Optional<@Base64 String> bs;
}

After a quick byte-code analysis (javap -v ... | grep Base64) the following scala code does not seem to compile properly:

case class SomeScalaBean(bs: Optional[String @Base64]) 

This was asked on SO: http://stackoverflow.com/questions/38833827/how-to-annotate-a-type-parameter-in-scala

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-9883?orig=1
Reporter: Bruno Bieth (mustaghattack)
Affected Versions: 2.11.8
See #9853

[tmoschou]

This is still an issue with annotation on type parameters being ignored by scalac. An example use case is implementing a custom Hibernate Validator ValueExtractor, which requires it.

See https://docs.jboss.org/hibernate/stable/validator/reference/en-US/html_single/#_implementing_a_code_valueextractor_code

import javax.validation.valueextraction.{ExtractedValue, ValueExtractor}
import javax.validation.{Validation, Validator}

object SeqValueExtractor extends ValueExtractor[Seq[_ @ExtractedValue]] {
  override def extractValues(
    originalValue: Seq[_],
    receiver: ValueExtractor.ValueReceiver
  ): Unit = {
    for ((x, i) <- originalValue.zipWithIndex) {
      receiver.indexedValue(null, i, x)
    }
  }
}

Validation
  .byDefaultProvider
  .configure
  .addValueExtractor(SeqValueExtractor)

Caused by: javax.validation.valueextraction.ValueExtractorDefinitionException: HV000203: Value extractor type io.stellargraph.storage.web.config.SeqValueExtractor$ fails to declare the extracted type parameter using @ExtractedValue.
	at org.hibernate.validator.internal.engine.valueextraction.ValueExtractorDescriptor.getExtractedTypeParameter(ValueExtractorDescriptor.java:95)
	at org.hibernate.validator.internal.engine.valueextraction.ValueExtractorDescriptor.<init>(ValueExtractorDescriptor.java:49)
	at org.hibernate.validator.internal.engine.ConfigurationImpl.addValueExtractor(ConfigurationImpl.java:219)
	at org.hibernate.validator.internal.engine.ConfigurationImpl.addValueExtractor(ConfigurationImpl.java:68)