Remove Validatable type

General cleanup, issue #46
Validatable was redundent with HeaderAppendable when using higher kinded types

core/src/main/scala/org/http4s/rho/PathBuilder.scala

@@ -18,13 +18,12 @@ import scala.reflect.runtime.universe.TypeTag
 
 /** Fully functional path building */
 final class PathBuilder[T <: HList](val method: Method, val path: PathRule)
-  extends HeaderAppendable[T]
-  with RouteExecutable[T]
+  extends RouteExecutable[T]
   with Decodable[T, Nothing]
   with UriConvertible
-  with Validatable[T]
+  with HeaderAppendable[T]
 {
-  type Self = PathBuilder[T]
+  type HeaderAppendResult[T <: HList] = Router[T]
 
   override def headers: HeaderRule = EmptyHeaderRule
 
@@ -51,9 +50,9 @@ final class PathBuilder[T <: HList](val method: Method, val path: PathRule)
   def /[T2 <: HList](t: RequestLineBuilder[T2])(implicit prep: Prepend[T2, T]): QueryBuilder[prep.Out] =
     QueryBuilder(method, PathAnd(path, t.path), t.query)
 
-  def toAction: Router[T] = validate(TypedHeader[HNil](EmptyHeaderRule))
+  def toAction: Router[T] = >>>(TypedHeader[HNil](EmptyHeaderRule))
 
-  override def validate[T1 <: HList](h2: TypedHeader[T1])(implicit prep: Prepend[T1, T]): Router[prep.Out] =
+  override def >>>[T1 <: HList](h2: TypedHeader[T1])(implicit prep: Prepend[T1, T]): Router[prep.Out] =
     Router(method, path, EmptyQuery, h2.rule)
 
   override def decoding[R](decoder: EntityDecoder[R]): CodecRouter[T, R] = CodecRouter(toAction, decoder)

core/src/main/scala/org/http4s/rho/QueryBuilder.scala

@@ -10,12 +10,13 @@ import shapeless.ops.hlist.Prepend
 import shapeless.{ ::, HList }
 
 case class QueryBuilder[T <: HList](method: Method,
-  path: PathRule,
-  query: QueryRule)
+                                      path: PathRule,
+                                     query: QueryRule)
   extends RouteExecutable[T]
   with HeaderAppendable[T]
-  with UriConvertible {
-  override type Self = QueryBuilder[T]
+  with UriConvertible
+{
+  override type HeaderAppendResult[T <: HList] = Router[T]
 
   override def makeAction[F](f: F, hf: HListToFunc[T, F]): RhoAction[T, F] =
     RhoAction(Router(method, path, query, headers), f, hf)

core/src/main/scala/org/http4s/rho/Router.scala

@@ -32,8 +32,7 @@ case class Router[T <: HList](method: Method,
                           with RoutingEntity[T]
                           with Decodable[T, Nothing]
 {
-
-  type Self = Router[T]
+  override type HeaderAppendResult[T <: HList] = Router[T]
 
   override def >>>[T2 <: HList](v: TypedHeader[T2])(implicit prep1: Prepend[T2, T]): Router[prep1.Out] =
     Router(method, path, query, HeaderAnd(headers, v.rule))
@@ -50,11 +49,14 @@ case class CodecRouter[T <: HList, R](router: Router[T], decoder: EntityDecoder[
            with RoutingEntity[R::T]
            with Decodable[T, R]
 {
-  type Self = CodecRouter[T, R]
+  override type HeaderAppendResult[T <: HList] = CodecRouter[T, R]
 
   override def >>>[T2 <: HList](v: TypedHeader[T2])(implicit prep1: Prepend[T2, T]): CodecRouter[prep1.Out,R] =
     CodecRouter(router >>> v, decoder)
 
+  /** Append the header to the builder, generating a new typed representation of the route */
+//  override def >>>[T2 <: HList](header: TypedHeader[T2])(implicit prep: Prepend[T2, T]): CodecRouter[prep.Out, R] = ???
+
   override def makeAction[F](f: F, hf: HListToFunc[R::T, F]): RhoAction[R::T, F] =
     new RhoAction(this, f, hf)
 

core/src/main/scala/org/http4s/rho/bits/HeaderAppendable.scala

@@ -1,6 +1,8 @@
 package org.http4s
 package rho.bits
 
+import scala.language.higherKinds
+
 import org.http4s.rho.bits.HeaderAST.TypedHeader
 import shapeless.HList
 import shapeless.ops.hlist.Prepend
@@ -9,8 +11,11 @@ import shapeless.ops.hlist.Prepend
   * @tparam T1 HList representation of the values to be extracted from the [[Request]]
   */
 trait HeaderAppendable[T1 <: HList] {
-  type Self <: HeaderAppendable[T1]
+  type HeaderAppendResult[T <: HList] <: HeaderAppendable[T]
 
   /** Append the header to the builder, generating a new typed representation of the route */
-  def >>>[T2 <: HList](header: TypedHeader[T2])(implicit prep: Prepend[T2, T1]): HeaderAppendable[prep.Out]
+  def >>>[T2 <: HList](header: TypedHeader[T2])(implicit prep: Prepend[T2, T1]): HeaderAppendResult[prep.Out]
+
+  final def validate[T2 <: HList](header: TypedHeader[T2])(implicit prep: Prepend[T2, T1]): HeaderAppendResult[prep.Out] =
+    >>>(header)(prep)
 }