Error in combination with a Simulacrum @typeclass

[alexandru]

Hello,

I've got this PR on the cats-effect project, trying to enable the sbt-unidoc plugin: typelevel/cats-effect#29

Unfortunately unidoc fails:

> unidoc
[info] Compiling 9 Scala sources to cats-effect/core/jvm/target/scala-2.12/classes...
[info] Main Scala API documentation to cats-effect/target/scala-2.12/unidoc...
[error] Symbol 'type cats.effect.Effect.ToEffectOps' is missing from the classpath.
[error] This symbol is required by 'package cats.effect.implicits.package'.
[error] Make sure that type ToEffectOps is in your classpath and check for conflicting dependencies with `-Ylog-classpath`.
[error] A full rebuild may help if 'package.class' was compiled against an incompatible version of cats.effect.Effect.
[info] No documentation generated with unsuccessful compiler run
[error] one error found
[error] (root/scalaunidoc:doc) Scaladoc generation failed
[error] Total time: 9 s, completed Apr 24, 2017 11:04:43 PM

The class it is complaining about is generated by a Simulacrum macro, see: https://github.com/mpilquist/simulacrum

Must mention that this error does not happen when running the normal doc command, so I think it is Unidoc related.

Please advise.

[xuwei-k]

#20 ?