title: Circe cannot find implicit encoder
body: <p>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.</p>
  
  <p>Here's the smallest example I was able to pare it down to.</p>
  
  <pre><code>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)
    }
  }
  </code></pre>
  
  <p>Which gives the following compile error</p>
  
  <blockquote>
    <p>Error:(30, 21) could not find implicit value for parameter encoder:
    io.circe.Encoder[OneCol]
        println(testVal.asJson)</p>
  </blockquote>
  
  <p>I have tried the same thing with semi-auto encoder creation</p>
  
  <pre><code>def main(args: Array[String]): Unit = {
    implicit val enc : Encoder[OneCol] = deriveEncoder
    val testVal = OneCol("someVal")
    println(testVal.asJson)
  }
  </code></pre>
  
  <p>Which gives the following errors</p>
  
  <blockquote>
    <p>Error:(25, 42) could not find Lazy implicit value of type
    io.circe.generic.encoding.DerivedObjectEncoder[A]
        implicit val enc : Encoder[OneCol] = deriveEncoder</p>
    
    <p>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</p>
  </blockquote>
  
  <p>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. </p>
  
  <p>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. </p>
  
  <p>Does anyone know why this is failing, and how to get it properly compiling?</p>
  
  <p>Edit:</p>
  
  <p>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.</p>
  
  <pre><code>        &lt;plugin&gt;
              &lt;groupId&gt;net.alchim31.maven&lt;/groupId&gt;
              &lt;artifactId&gt;scala-maven-plugin&lt;/artifactId&gt;
              &lt;configuration&gt;
                  &lt;args&gt;
                      &lt;!-- work-around for https://issues.scala-lang.org/browse/SI-8358 --&gt;
                      &lt;arg&gt;-nobootcp&lt;/arg&gt;
                  &lt;/args&gt;
                  &lt;recompileMode&gt;incremental&lt;/recompileMode&gt;
                  &lt;compilerPlugins&gt;
                      &lt;compilerPlugin&gt;
                          &lt;groupId&gt;org.scalamacros&lt;/groupId&gt;
                          &lt;artifactId&gt;paradise_2.10.4&lt;/artifactId&gt;
                          &lt;version&gt;2.1.0&lt;/version&gt;
                      &lt;/compilerPlugin&gt;
                      &lt;!--&lt;compilerPlugin&gt;--&gt;
                          &lt;!--&lt;groupId&gt;org.scala-lang.plugins&lt;/groupId&gt;--&gt;
                          &lt;!--&lt;artifactId&gt;macro-paradise_2.10.2&lt;/artifactId&gt;--&gt;
                          &lt;!--&lt;version&gt;2.0.0-SNAPSHOT&lt;/version&gt;--&gt;
                      &lt;!--&lt;/compilerPlugin&gt;--&gt;
                  &lt;/compilerPlugins&gt;
              &lt;/configuration&gt;
              &lt;executions&gt;
                  &lt;execution&gt;
                      &lt;id&gt;scala-compile-first&lt;/id&gt;
                      &lt;phase&gt;process-resources&lt;/phase&gt;
                      &lt;goals&gt;
                          &lt;goal&gt;compile&lt;/goal&gt;
                      &lt;/goals&gt;
                  &lt;/execution&gt;
                  &lt;execution&gt;
                      &lt;id&gt;scala-test-compile-first&lt;/id&gt;
                      &lt;phase&gt;process-test-resources&lt;/phase&gt;
                      &lt;goals&gt;
                          &lt;goal&gt;testCompile&lt;/goal&gt;
                      &lt;/goals&gt;
                  &lt;/execution&gt;
              &lt;/executions&gt;
          &lt;/plugin&gt;
  </code></pre>