not found: value λ

Any idea why I can use * but not λ?

sbt:hedgehog> show Test/libraryDependencies
[info] test / Test / libraryDependencies
[info] 	List(org.scala-lang:scala-library:2.12.11, org.typelevel:kind-projector:0.11.0:plugin->default(compile))
[info] runner / Test / libraryDependencies
[info] 	List(org.scala-lang:scala-library:2.12.11, org.typelevel:kind-projector:0.11.0:plugin->default(compile))
[info] example / Test / libraryDependencies
[info] 	List(org.scala-lang:scala-library:2.12.11, org.typelevel:kind-projector:0.11.0:plugin->default(compile))
[info] sbt-test / Test / libraryDependencies
[info] 	List(org.scala-lang:scala-library:2.12.11, org.typelevel:kind-projector:0.11.0:plugin->default(compile), org.scala-sbt:test-interface:1.0)
[info] core / Test / libraryDependencies
[info] 	List(org.scala-lang:scala-library:2.12.11, org.typelevel:kind-projector:0.11.0:plugin->default(compile))
[info] Test / libraryDependencies
[info] 	List(org.scala-lang:scala-library:2.12.11, org.typelevel:kind-projector:0.11.0:plugin->default(compile))
sbt:hedgehog> Test/compile
[info] Compiling 18 Scala sources to /Users/jason/source/scala-hedgehog/test/target/scala-2.12/test-classes ...
[error] /Users/jason/source/scala-hedgehog/test/src/test/scala/hedgehog/core/TreeTest.scala:8:28: not found: value λ
[error]   private val ToProperty = λ[PF1[Tree, PropertyT]](treeProperty)
[error]                            ^
[error] /Users/jason/source/scala-hedgehog/test/src/test/scala/hedgehog/core/TreeTest.scala:8:52: missing argument list for method treeProperty in object TreeTest
[error] Unapplied methods are only converted to functions when a function type is expected.
[error] You can make this conversion explicit by writing `treeProperty _` or `treeProperty(_)` instead of `treeProperty`.
[error]   private val ToProperty = λ[PF1[Tree, PropertyT]](treeProperty)
[error]                                                    ^
[error] /Users/jason/source/scala-hedgehog/test/src/test/scala/hedgehog/core/TreeTest.scala:8:15: private val ToProperty in object TreeTest is never used
[error]   private val ToProperty = λ[PF1[Tree, PropertyT]](treeProperty)
[error]               ^
[error] /Users/jason/source/scala-hedgehog/test/src/test/scala/hedgehog/core/TreeTest.scala:15:15: private method treeProperty in object TreeTest is never used
[error]   private def treeProperty[A](tree: Tree[A]): PropertyT[A] =
[error]               ^
[error] /Users/jason/source/scala-hedgehog/test/src/test/scala/hedgehog/predef/EitherTest.scala:10:28: not found: value λ
[error]   private val ToProperty = λ[PF1[Either[Nothing, *], PropertyT]](eitherProperty)
[error]                            ^
[error] /Users/jason/source/scala-hedgehog/test/src/test/scala/hedgehog/predef/EitherTest.scala:10:66: missing argument list for method eitherProperty in object EitherTest
[error] Unapplied methods are only converted to functions when a function type is expected.
[error] You can make this conversion explicit by writing `eitherProperty _` or `eitherProperty(_)` instead of `eitherProperty`.
[error]   private val ToProperty = λ[PF1[Either[Nothing, *], PropertyT]](eitherProperty)
[error]                                                                  ^
[error] /Users/jason/source/scala-hedgehog/test/src/test/scala/hedgehog/predef/EitherTest.scala:5:30: Unused import
[error] import hedgehog.predef.Monad._
[error]                              ^
[error] /Users/jason/source/scala-hedgehog/test/src/test/scala/hedgehog/predef/EitherTest.scala:10:15: private val ToProperty in object EitherTest is never used
[error]   private val ToProperty = λ[PF1[Either[Nothing, *], PropertyT]](eitherProperty)
[error]               ^
[error] /Users/jason/source/scala-hedgehog/test/src/test/scala/hedgehog/predef/EitherTest.scala:17:15: private method eitherProperty in object EitherTest is never used
[error]   private def eitherProperty[A](either: Either[Nothing, A]): PropertyT[A] =
[error]               ^
[error] /Users/jason/source/scala-hedgehog/test/src/test/scala/hedgehog/predef/IdTest.scala:10:28: not found: value λ
[error]   private val ToProperty = λ[PF1[Id, PropertyT]](identityProperty)
[error]                            ^
[error] 21 errors found
[error] (test / Test / compileIncremental) Compilation failed
[error] Total time: 1 s, completed 4/04/2020, 9:54:15 am

Someone else has the same problem on StackOverflow https://stackoverflow.com/questions/48767385/kind-compiler-plugin-%CE%BB-not-found

Start by reproducing the failure with sbt Test/compile, then inspect the λ usages in test/src/test/scala/hedgehog/core/TreeTest.scala, hedgehog/predef/EitherTest.scala, and hedgehog/predef/IdTest.scala. Compare the kind-projector configuration and imports used by these tests with the plugin setup shown in the dependency output. Done means the test sources compile successfully without the not-found errors.