build.gradle

plugins {
    id 'scala'
}

configurations {
    scalaCompilerPlugin
}

dependencies {
    // Use Scala 2.11 in our library project
    compile 'org.scala-lang:scala-library:2.12.6'
    compile 'io.estatico:newtype_2.12:0.4.2'
    scalaCompilerPlugin 'org.scalamacros:paradise_2.12.6:2.1.1'


    // Use Scalatest for testing our library
    testCompile 'junit:junit:4.12'
    testCompile 'org.scalatest:scalatest_2.12:3.0.5'

    // Need scala-xml at test runtime
    testRuntime 'org.scala-lang.modules:scala-xml_2.12:1.1.0'
}


repositories {
    jcenter()
}

tasks.withType(ScalaCompile){
    // Map plugin jars to -Xplugin parameter
    List<String> parameters =
    configurations.scalaCompilerPlugin.files.collect {
        '-Xplugin:'+ it.absolutePath
    }

    // Add existing parameters
    List<String> existingParameters = scalaCompileOptions.additionalParameters
    if (existingParameters) {
        parameters.addAll(existingParameters)
    }

    // Add whatever flags you typically add
    parameters += [
            '-language:implicitConversions',
            '-language:higherKinds'
    ]
    
    // Finally set the additionalParameters
    scalaCompileOptions.additionalParameters = parameters
}