Make WithFilter capture checked

Author: odersky

tests/pos-special/stdlib/collection/Iterable.scala

@@ -905,7 +905,7 @@ object IterableOps {
     def map[B](f: A => B): CC[B]^{this, f} =
       self.iterableFactory.from(new View.Map(filtered, f))
 
-    def flatMap[B](f: A => IterableOnce[B]): CC[B]^{this, f} =
+    def flatMap[B](f: A => IterableOnce[B]^): CC[B]^{this, f} =
       self.iterableFactory.from(new View.FlatMap(filtered, f))
 
     def foreach[U](f: A => U): Unit = filtered.foreach(f)

tests/pos-special/stdlib/collection/Map.scala

@@ -378,13 +378,13 @@ object MapOps {
     p: ((K, V)) => Boolean
   ) extends IterableOps.WithFilter[(K, V), IterableCC](self, p) with Serializable {
 
-    def map[K2, V2](f: ((K, V)) => (K2, V2)): CC[K2, V2] =
+    def map[K2, V2](f: ((K, V)) => (K2, V2)): CC[K2, V2]^{this, f} =
       self.mapFactory.from(new View.Map(filtered, f))
 
-    def flatMap[K2, V2](f: ((K, V)) => IterableOnce[(K2, V2)]^): CC[K2, V2] =
+    def flatMap[K2, V2](f: ((K, V)) => IterableOnce[(K2, V2)]^): CC[K2, V2]^{this, f} =
       self.mapFactory.from(new View.FlatMap(filtered, f))
 
-    override def withFilter(q: ((K, V)) => Boolean): WithFilter[K, V, IterableCC, CC]^{p, q} =
+    override def withFilter(q: ((K, V)) => Boolean): WithFilter[K, V, IterableCC, CC]^{this, q} =
       new WithFilter[K, V, IterableCC, CC](self, (kv: (K, V)) => p(kv) && q(kv))
 
   }

tests/pos-special/stdlib/collection/WithFilter.scala

@@ -11,6 +11,7 @@
  */
 
 package scala.collection
+import language.experimental.captureChecking
 
 /** A template trait that contains just the `map`, `flatMap`, `foreach` and `withFilter` methods
   * of trait `Iterable`.
@@ -22,6 +23,7 @@ package scala.collection
   */
 @SerialVersionUID(3L)
 abstract class WithFilter[+A, +CC[_]] extends Serializable {
+  this: WithFilter[A, CC]^ =>
 
   /** Builds a new collection by applying a function to all elements of the
     * `filtered` outer $coll.
@@ -32,7 +34,7 @@ abstract class WithFilter[+A, +CC[_]] extends Serializable {
     *                the given function `f` to each element of the filtered outer $coll
     *                and collecting the results.
     */
-  def map[B](f: A => B): CC[B]
+  def map[B](f: A => B): CC[B]^{this, f}
 
   /** Builds a new collection by applying a function to all elements of the
     * `filtered` outer $coll containing this `WithFilter` instance that satisfy
@@ -44,7 +46,7 @@ abstract class WithFilter[+A, +CC[_]] extends Serializable {
     *                of the filtered outer $coll and
     *                concatenating the results.
     */
-  def flatMap[B](f: A => IterableOnce[B]): CC[B]
+  def flatMap[B](f: A => IterableOnce[B]^): CC[B]^{this, f}
 
   /** Applies a function `f` to all elements of the `filtered` outer $coll.
     *
@@ -65,6 +67,6 @@ abstract class WithFilter[+A, +CC[_]] extends Serializable {
     *             All these operations apply to those elements of this $coll which
     *             also satisfy both `p` and `q` predicates.
     */
-  def withFilter(q: A => Boolean): WithFilter[A, CC]
+  def withFilter(q: A => Boolean): WithFilter[A, CC]^{this, q}
 
 }