Circe无法找到隐式编码器

Question

I am trying to encode a few classes into json strings, however no matter what I try, my classes do not seem to be able to find an implicit encoder for the case classes I am using.

Here's the smallest example I was able to pare it down to.

import io.circe._
import io.circe.generic.semiauto._
import io.circe.generic.auto._
import io.circe.syntax._

case class OneCol(value: String)

object testObject {
  def main(args: Array[String]): Unit = {
    val testVal = OneCol("someVal")
    println(testVal.asJson)
  }
}

Which gives the following compile error

Error:(30, 21) could not find implicit value for parameter encoder: io.circe.Encoder[OneCol] println(testVal.asJson)

I have tried the same thing with semi-auto encoder creation

def main(args: Array[String]): Unit = {
  implicit val enc : Encoder[OneCol] = deriveEncoder
  val testVal = OneCol("someVal")
  println(testVal.asJson)
}

Which gives the following errors

Error:(25, 42) could not find Lazy implicit value of type io.circe.generic.encoding.DerivedObjectEncoder[A] implicit val enc : Encoder[OneCol] = deriveEncoder

Error:(25, 42) not enough arguments for method deriveEncoder: (implicit encode: shapeless.Lazy[io.circe.generic.encoding.DerivedObjectEncoder[A]])io.circe.ObjectEncoder[A]. Unspecified value parameter encode. implicit val enc : Encoder[OneCol] = deriveEncoder

I am fairly sure that the entire purpose of auto and semi-auto encoder generation is to handle situations like these, so I am at a bit of a loss as to what I am doing wrong.

I am using scala 2.10.4, and circe 0.7.0 (circe-core_2.10, circe-generic_2.10 artifacts) if version information is relevant, with maven as the package manager.

Does anyone know why this is failing, and how to get it properly compiling?

Edit:

Here's the section of my POM with the macros plugin. Have tried both compiler plugins listed (both commented and non-commented), and both still give the same error.

        <plugin>
            <groupId>net.alchim31.maven</groupId>
            <artifactId>scala-maven-plugin</artifactId>
            <configuration>
                <args>
                    <!-- work-around for https://issues.scala-lang.org/browse/SI-8358 -->
                    <arg>-nobootcp</arg>
                </args>
                <recompileMode>incremental</recompileMode>
                <compilerPlugins>
                    <compilerPlugin>
                        <groupId>org.scalamacros</groupId>
                        <artifactId>paradise_2.10.4</artifactId>
                        <version>2.1.0</version>
                    </compilerPlugin>
                    <!--<compilerPlugin>-->
                        <!--<groupId>org.scala-lang.plugins</groupId>-->
                        <!--<artifactId>macro-paradise_2.10.2</artifactId>-->
                        <!--<version>2.0.0-SNAPSHOT</version>-->
                    <!--</compilerPlugin>-->
                </compilerPlugins>
            </configuration>
            <executions>
                <execution>
                    <id>scala-compile-first</id>
                    <phase>process-resources</phase>
                    <goals>
                        <goal>compile</goal>
                    </goals>
                </execution>
                <execution>
                    <id>scala-test-compile-first</id>
                    <phase>process-test-resources</phase>
                    <goals>
                        <goal>testCompile</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>

Answer 1

It turns out that circe-core_2.10 has a dependency on scala version 2.10.6, meaning that my version of scala (2.10.4) was incompatible with the library, causing the issues. Upgrading to the proper version of scala fixed this.