scala-2.10

In Scala 2.9 one could implement polymorphic instantiation as def newInstance[T](implicit m: Manifest[T]) = m.erasure.newInstance.asInstanceOf[T] but as of 2.10 Manifest is being replaced with TypeTag , and it is not clear to me how to achieve something similar with TypeTag . I would prefer if the TypeTag version preserved all available type information. I know that the above only works for traits/classes that do not require constructor args, and ven then it does not always work, but it works well enough for what I need. If I can do better the new reflection APIs that would be great. TypeTag

Our library uses TypeTags, but now we need to interact with another library which requires Manifests. Is there any simple way to create a Manifest from a TypeTag? gourlaysama's anwer uses Class[_], thus type arguments are being erased. I've come up with an implementation that preserves the type arguments here: How to maintain type parameter during TypeTag to Manifest conversion? Here's the code: def toManifest[T:TypeTag]: Manifest[T] = { val t = typeTag[T] val mirror = t.mirror def toManifestRec(t: Type): Manifest[_] = { val clazz = ClassTag[T](mirror.runtimeClass(t)).runtimeClass if (t

I am working in a Scala embedded DSL and macros are becoming a main tool for achieving my purposes. I am getting an error while trying to reuse a subtree from the incoming macro expression into the resulting one. The situation is quite complex, but (I hope) I have simplified it for its understanding. Suppose we have this code: val y = transform { val x = 3 x } println(y) // prints 3 where 'transform' is the involved macro. Although it could seem it does absolutely nothing, it is really transforming the shown block into this expression: 3 match { case x => x } It is done with this macro

When compiling an application with Play2, sometimes these kind of message appears on my terminal : [info] Compiling 1 Scala source to ~/target/scala-2.10/classes... [warn] there were 1 feature warnings; re-run with -feature for details [warn] one warning found [success] Compiled in 1s How can I get more information about those warning? It must be an option of sbt but I have no idea where to search... om-nom-nom To see the exact message you need to add "feature" flag in your sbt build definition file: scalacOptions ++= Seq("-feature") Why? Scala 2.10 not only introduced new features, but also

I'm documenting a Scala class with overloaded methods . How can I distinguish them when referring to them in scaladoc comments? For example, if I have /** * The most important method is [[Doc.foo]]. */ object Doc { def foo[A]: A = throw new UnsupportedOperationException; def foo[A,B >: A](x: A): B = x; } and run sbt doc I get Doc.scala:1: warning: The link target "Doc.foo" is ambiguous. Several (possibly overloaded) members fit the target: method foo[A,B>:A](x:A):B in object Doc [chosen] method foo[A]:Nothing in object Doc Using foo[A,B >: A] etc. to the link doesn't work. The following seems

I'm digging new scala reflection api and can't figure out why the following snippet doesn't work as expected. Given hierarchy (tried to simplify as much as I can): import scala.reflect.runtime.universe._ trait TF[A] { implicit def t: TypeTag[A] def f[T <: A: TypeTag]: PartialFunction[Any, A] = { case msg: T if typeOf[T] =:= typeOf[A] => msg } } class TFilter[T: TypeTag] extends TF[T] { def t = typeTag[T] } case class Foo(x: Int) I expect method f to filter objects of given type. So the following snippet should return Seq[Foo] val messages = Seq(1, "hello", Foo(1)) val tFilter = new TFilter[Foo