small tree attachment refactoring: firstAttachment

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -2209,7 +2209,8 @@ trait Typers extends Modes with Adaptations with Taggings with PatMatVirtualiser
     def adaptCase(cdef: CaseDef, mode: Int, tpe: Type): CaseDef = deriveCaseDef(cdef)(adapt(_, mode, tpe))
 
     // takes untyped sub-trees of a match and type checks them
-    def typedMatch(selector0: Tree, cases: List[CaseDef], mode: Int, resTp: Type) = {
+    def typedMatch(selector0: Tree, cases: List[CaseDef], mode: Int, resTp: Type): Match = {
+      // strip off the annotation as it won't type check
       val (selector, doTranslation) = selector0 match {
         case Annotated(Ident(nme.synthSwitch), selector) => (selector, false)
         case s => (s, true)

src/library/scala/reflect/api/Trees.scala

@@ -110,13 +110,12 @@ trait Trees { self: Universe =>
     def withoutAttachment(att: Any): this.type = { detach(att); this }
     def attachment[T: ClassTag]: T = attachmentOpt[T] getOrElse { throw new Error("no attachment of type %s".format(classTag[T].erasure)) }
     def attachmentOpt[T: ClassTag]: Option[T] =
+      firstAttachment { case attachment if attachment.getClass == classTag[T].erasure => attachment.asInstanceOf[T] }
+
+    def firstAttachment[T](p: PartialFunction[Any, T]): Option[T] =
       rawatt match {
-        case NontrivialAttachment(pos, payload) =>
-          val index = payload.indexWhere(p => p.getClass == classTag[T].erasure)
-          if (index != -1) Some(payload(index).asInstanceOf[T])
-          else None
-        case _ =>
-          None
+        case NontrivialAttachment(pos, payload) => payload.collectFirst(p)
+        case _ => None
       }
 
     private[this] var rawtpe: Type = _