scala-macros

问题 I'm trying to build a simple typeclass IsEnum[T] using a macro. I use knownDirectSubclasses to get all the direct subclasses if T , ensure T is a sealed trait, and that all subclasses are of case objects (using subSymbol.asClass.isModuleClass && subSymbol.asClass.isCaseClass ). Now I'm trying to build a Seq with the case objects referred by the subclasses. It's working, using a workaround: Ident(subSymbol.asInstanceOf[scala.reflect.internal.Symbols#Symbol].sourceModule.asInstanceOf[Symbol])

问题 I'm trying to build a simple typeclass IsEnum[T] using a macro. I use knownDirectSubclasses to get all the direct subclasses if T , ensure T is a sealed trait, and that all subclasses are of case objects (using subSymbol.asClass.isModuleClass && subSymbol.asClass.isCaseClass ). Now I'm trying to build a Seq with the case objects referred by the subclasses. It's working, using a workaround: Ident(subSymbol.asInstanceOf[scala.reflect.internal.Symbols#Symbol].sourceModule.asInstanceOf[Symbol])

问题 I'm trying to build a simple typeclass IsEnum[T] using a macro. I use knownDirectSubclasses to get all the direct subclasses if T , ensure T is a sealed trait, and that all subclasses are of case objects (using subSymbol.asClass.isModuleClass && subSymbol.asClass.isCaseClass ). Now I'm trying to build a Seq with the case objects referred by the subclasses. It's working, using a workaround: Ident(subSymbol.asInstanceOf[scala.reflect.internal.Symbols#Symbol].sourceModule.asInstanceOf[Symbol])

问题 I'm writing a Scala program and I want it to work with two version of a big library. This big library's version 2 changes the API very slightly (only one class constructor signature has an extra parameter). // Lib v1 class APIClass(a: String, b:Integer){ ... } // Lib v2 class APIClass(a: String, b: Integer, c: String){ ... } // And my code extends APIClass.. And I have no #IFDEF class MyClass() extends APIClass("x", 1){ // <-- would be APIClass("x", 1, "y") in library v2 ... } I really don't

问题 My code compiles with the following error: Macro expansion contains free term variable Hello ... I have reduced it to minimal example: class Hello(val hi: String) { val xx = reify(hi) var yy = q"" } def setYYImpl(c: Context)(hExpr: c.Expr[Hello]): c.Expr[Hello] = { import c.universe._ val hello = c.eval(c.Expr[Hello](c.untypecheck(hExpr.tree.duplicate))) val xxVal = c.internal.createImporter(u).importTree(hello.xx.tree) c.Expr(q"""{val h = new Hello("HO"); h.yy=$xxVal; h}""") // it should set

问题 My code compiles with the following error: Macro expansion contains free term variable Hello ... I have reduced it to minimal example: class Hello(val hi: String) { val xx = reify(hi) var yy = q"" } def setYYImpl(c: Context)(hExpr: c.Expr[Hello]): c.Expr[Hello] = { import c.universe._ val hello = c.eval(c.Expr[Hello](c.untypecheck(hExpr.tree.duplicate))) val xxVal = c.internal.createImporter(u).importTree(hello.xx.tree) c.Expr(q"""{val h = new Hello("HO"); h.yy=$xxVal; h}""") // it should set

问题 I would like to wrap all the user defined functions in a scala project that return a certain type T , into a function that accepts a T and the function name as parameters. eg. given this function is in scope: def withMetrics[T](functionName: String)(f: => Try[T]): Try[T] = { f match { case _: Success[T] => println(s"send metric: success for $functionName") case _: Failure[T] => println(s"send metric: failure for $functionName") } f } the user can send metrics for their functions which return

问题 I would like to wrap all the user defined functions in a scala project that return a certain type T , into a function that accepts a T and the function name as parameters. eg. given this function is in scope: def withMetrics[T](functionName: String)(f: => Try[T]): Try[T] = { f match { case _: Success[T] => println(s"send metric: success for $functionName") case _: Failure[T] => println(s"send metric: failure for $functionName") } f } the user can send metrics for their functions which return

问题 I would like to wrap all the user defined functions in a scala project that return a certain type T , into a function that accepts a T and the function name as parameters. eg. given this function is in scope: def withMetrics[T](functionName: String)(f: => Try[T]): Try[T] = { f match { case _: Success[T] => println(s"send metric: success for $functionName") case _: Failure[T] => println(s"send metric: failure for $functionName") } f } the user can send metrics for their functions which return

问题 I don't even know how to ask the question. I have a macro that creates an instance of IsEnum[T] for a type T . I'm doing testing for it, and want to make sure that the implicit is not found for types that are not sealed, or that, in general, don't meet the requirements of an enum. So I created this method for testing def enumOf[T](implicit isEnum:IsEnum[T] = null) = isEnum And then I ensure that enumOf[NotAnEnum] == null But instead, it fails at compile time. One thing is the macro erroring.