dyn.scala

      InputKey[Unit]("charts") := Def.inputTaskDyn {
        val targetDir = crossTarget.value
        val report = targetDir / "report.json"
        Def.task {
          val _ = (run in Compile).fullInput(s" ${report.absolutePath}").evaluated
          //                                 ^ Illegal dynamic dependency
          strawman.collection.Bencharts(report, "Memory footprint (lower is better)", targetDir)
        }
      }.inputTaskValue

input.scala

      InputKey[Unit]("charts") := {
        val targetDir = crossTarget.value
        val report = targetDir / "report.json"
        val _ = (run in Compile).fullInput(s" ${report.absolutePath}").evaluated
        //                                 ^ Illegal dynamic reference: report
        strawman.collection.Bencharts(report, "Memory footprint (lower is better)", targetDir)
      }