Created
August 12, 2016 15:58
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| trait TypeclassA[A] { } | |
| trait TypeclassB[A] { } | |
| trait TypeclassC[A] { | |
| implicit val typeAInstance: TypeclassA[A] | |
| implicit val typeBInstance: TypeclassB[A] | |
| } | |
| object TypeclassC { | |
| /** | |
| * Helper function for creating TypeclassC instances | |
| */ | |
| def mkInstance[A](implicit ev1: TypeclassA[A], ev2: TypeclassB[A]) = new TypeclassC[A] { | |
| implicit val typeAInstance = ev1 | |
| implicit val typeBInstance = ev2 | |
| } | |
| } | |
| object Test { | |
| import TypeclassC.mkInstance | |
| implicit val tAInt: TypeclassA[Int] = new TypeclassA[Int] {} | |
| implicit val tBInt: TypeclassB[Int] = new TypeclassB[Int] {} | |
| implicit val tCInt = mkInstance[Int] // compiles | |
| implicit val tCString = mkInstance[String] // does NOT compile | |
| } |
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