Add explicit suchThat to Gen.conatainerOf combinators.

This also restricts Gen.containerOf to only handle
types that are implicitly convertible to Traversable.
This is required in order to be able to inspect
simplified containers.

src/main/scala/org/scalacheck/Arbitrary.scala

@@ -268,16 +268,18 @@ object Arbitrary {
   implicit def arbEither[T, U](implicit at: Arbitrary[T], au: Arbitrary[U]): Arbitrary[Either[T, U]] =
     Arbitrary(oneOf(arbitrary[T].map(Left(_)), arbitrary[U].map(Right(_))))
 
-  /** Arbitrary instance of any [[org.scalacheck.util.Buildable]] container (such as lists, arrays,
-   *  streams, etc). The maximum size of the container depends on the size
-   *  generation parameter. */
-  implicit def arbContainer[C[_],T](implicit a: Arbitrary[T], b: Buildable[T,C]
+  /** Arbitrary instance of any [[org.scalacheck.util.Buildable]] container
+   *  (such as lists, arrays, streams, etc). The maximum size of the container
+   *  depends on the size generation parameter. */
+  implicit def arbContainer[C[_],T](implicit
+    a: Arbitrary[T], b: Buildable[T,C], t: C[T] => Traversable[T]
   ): Arbitrary[C[T]] = Arbitrary(containerOf[C,T](arbitrary[T]))
 
-  /** Arbitrary instance of any [[org.scalacheck.util.Buildable2]] container (such as maps, etc).
-   *  The maximum size of the container depends on the size
+  /** Arbitrary instance of any [[org.scalacheck.util.Buildable2]] container
+   *  (such as maps, etc). The maximum size of the container depends on the size
    *  generation parameter. */
-  implicit def arbContainer2[C[_,_],T,U](implicit a: Arbitrary[(T,U)], b: Buildable2[T,U,C]
+  implicit def arbContainer2[C[_,_],T,U](implicit
+    a: Arbitrary[(T,U)], b: Buildable2[T,U,C], t: C[T,U] => Traversable[(T,U)]
   ): Arbitrary[C[T,U]] = Arbitrary(containerOf[C,T,U](arbitrary[(T,U)]))
 
   // Functions //

src/main/scala/org/scalacheck/Gen.scala

@@ -266,10 +266,7 @@ object Gen {
         case (rs,g) => g.doApply(p).flatMap(r => rs.map(_ :+ r))
       }
     }
-    val sieve = gs.foldLeft((_:T) => false) { case (s,g) =>
-      x:T => s(x) || g.sieveCopy(x)
-    }
-    g.map(b.fromIterable) // TODO .suchThat(_.forall(sieve))
+    g.map(b.fromIterable)
   }
 
   /** Sequences generators. If any of the given generators fails, the
@@ -280,10 +277,7 @@ object Gen {
         case (rs,g) => g.doApply(p).flatMap(r => rs.map(_ :+ r))
       }
     }
-    val sieve = gs.foldLeft((_:T) => false) { case (s,g) =>
-      x:T => s(x) || g.sieveCopy(x)
-    }
-    g.map(b.fromIterable) // TODO .suchThat(_.forall(sieve))
+    g.map(b.fromIterable)
   }
 
   /** Wraps a generator lazily. The given parameter is only evaluated once,
@@ -348,57 +342,84 @@ object Gen {
 
   //// List Generators ////
 
-  /** Generates a container of any type for which there exists an implicit
+  /** Generates a container of any Traversable type for which there exists an implicit
    *  [[org.scalacheck.util.Buildable]] instance. The elements in the container will
    *  be generated by the given generator. The size of the generated container
    *  is given by `n`. If the given generator fails generating a value, the
-   *  complete container gnerator will also fail. */
-  def containerOfN[C[_],T](n: Int, g: Gen[T])(implicit b: Buildable[T,C]
-  ): Gen[C[T]] = sequence[C,T](Traversable.fill(n)(g))
-
-  /** Generates a container of any type for which there exists an implicit
-   *  [[org.scalacheck.util.Buildable]] instance. The elements in the container
-   *  will be generated by the given generator. The size of the container is
-   *  bounded by the size parameter used when generating values. */
-  def containerOf[C[_],T](g: Gen[T])(implicit b: Buildable[T,C]): Gen[C[T]] =
-    sized(size => choose(0,size).flatMap(containerOfN[C,T](_,g)))
+   *  complete container generator will also fail. */
+  def containerOfN[C[_],T](n: Int, g: Gen[T])(implicit
+    evb: Buildable[T,C], evt: C[T] => Traversable[T]
+  ): Gen[C[T]] =
+    sequence[C,T](Traversable.fill(n)(g)) suchThat { c =>
+      c.size == n && c.forall(g.sieveCopy)
+    }
 
-  /** Generates a non-empty container of any type for which there exists an
+  /** Generates a container of any Traversable type for which there exists an
    *  implicit [[org.scalacheck.util.Buildable]] instance. The elements in the
    *  container will be generated by the given generator. The size of the
    *  container is bounded by the size parameter used when generating values. */
-  def nonEmptyContainerOf[C[_],T](g: Gen[T])(implicit b: Buildable[T,C]): Gen[C[T]] =
-    sized(size => choose(1,size).flatMap(containerOfN[C,T](_,g)))
+  def containerOf[C[_],T](g: Gen[T])(implicit
+    evb: Buildable[T,C], evt: C[T] => Traversable[T]
+  ): Gen[C[T]] =
+    sized(s => choose(0,s).flatMap(containerOfN[C,T](_,g))) suchThat { c =>
+      c.forall(g.sieveCopy)
+    }
 
-  /** Generates a non-empty container of any type for which there exists an
-   *  implicit [[org.scalacheck.util.Buildable]] instance. The elements in the
-   *  container will be generated by the given generator. The size of the
-   *  container is bounded by the size parameter used when generating values. */
-  @deprecated("Use Gen.nonEmptyContainerOf instead", "1.11.0")
-  def containerOf1[C[_],T](g: Gen[T])(implicit b: Buildable[T,C]): Gen[C[T]] =
-    nonEmptyContainerOf[C,T](g)
+  /** Generates a non-empty container of any Traversable type for which there
+   *  exists an implicit [[org.scalacheck.util.Buildable]] instance. The
+   *  elements in the container will be generated by the given generator. The
+   *  size of the container is bounded by the size parameter used when
+   *  generating values. */
+  def nonEmptyContainerOf[C[_],T](g: Gen[T])(implicit
+    evb: Buildable[T,C], evt: C[T] => Traversable[T]
+  ): Gen[C[T]] =
+    sized(s => choose(1,s).flatMap(containerOfN[C,T](_,g))) suchThat { c =>
+      c.size > 0 && c.forall(g.sieveCopy)
+    }
 
-  /** Generates a container of any type for which there exists an implicit
-   *  [[org.scalacheck.util.Buildable2]] instance. The elements in the container will
-   *  be generated by the given generator. The size of the generated container
-   *  is given by `n`. If the given generator fails generating a value, the
-   *  complete container gnerator will also fail. */
-  def containerOfN[C[_,_],T,U](n: Int, g: Gen[(T,U)])(implicit b: Buildable2[T,U,C]
-  ): Gen[C[T,U]] = sequence[C,T,U](Traversable.fill(n)(g))
+  /** Generates a non-empty container of any Traversable type for which there
+   *  exists an implicit [[org.scalacheck.util.Buildable]] instance. The
+   *  elements in the container will be generated by the given generator. The
+   *  size of the container is bounded by the size parameter used when
+   *  generating values. */
+  @deprecated("Use Gen.nonEmptyContainerOf instead", "1.11.0")
+  def containerOf1[C[_],T](g: Gen[T])(implicit
+    evb: Buildable[T,C], evt: C[T] => Traversable[T]
+  ): Gen[C[T]] = nonEmptyContainerOf[C,T](g)
+
+  /** Generates a container of any Traversable type for which there exists an
+   *  implicit [[org.scalacheck.util.Buildable2]] instance. The elements in
+   *  the container will be generated by the given generator. The size of the
+   *  generated container is given by `n`. If the given generator fails
+   *  generating a value, the complete container generator will also fail. */
+  def containerOfN[C[_,_],T,U](n: Int, g: Gen[(T,U)])(implicit
+    evb: Buildable2[T,U,C], evt: C[T,U] => Traversable[(T,U)]
+  ): Gen[C[T,U]] =
+    sequence[C,T,U](Traversable.fill(n)(g)).suchThat { c =>
+      c.size == n && c.forall(g.sieveCopy)
+    }
 
-  /** Generates a container of any type for which there exists an implicit
-   *  <code>Buildable2</code> instance. The elements in the container will
-   *  be generated by the given generator. The size of the container is
-   *  bounded by the size parameter used when generating values. */
-  def containerOf[C[_,_],T,U](g: Gen[(T,U)])(implicit b: Buildable2[T,U,C]): Gen[C[T,U]] =
-    sized(size => for(n <- choose(0,size); c <- containerOfN[C,T,U](n,g)) yield c)
+  /** Generates a container of any Traversable type for which there exists
+   *  an implicit <code>Buildable2</code> instance. The elements in the
+   *  container will be generated by the given generator. The size of the
+   *  container is bounded by the size parameter used when generating values. */
+  def containerOf[C[_,_],T,U](g: Gen[(T,U)])(implicit
+    evb: Buildable2[T,U,C], evt: C[T,U] => Traversable[(T,U)]
+  ): Gen[C[T,U]] =
+    sized(s => choose(0,s).flatMap(containerOfN[C,T,U](_,g))) suchThat { c =>
+      c.forall(g.sieveCopy)
+    }
 
   /** Generates a non-empty container of any type for which there exists an
    *  implicit <code>Buildable2</code> instance. The elements in the container
    *  will be generated by the given generator. The size of the container is
    *  bounded by the size parameter used when generating values. */
-  def nonEmptyContainerOf[C[_,_],T,U](g: Gen[(T,U)])(implicit b: Buildable2[T,U,C]): Gen[C[T,U]] =
-    sized(size => for(n <- choose(1,size); c <- containerOfN[C,T,U](n,g)) yield c)
+  def nonEmptyContainerOf[C[_,_],T,U](g: Gen[(T,U)])(implicit
+    evb: Buildable2[T,U,C], evt: C[T,U] => Traversable[(T,U)]
+  ): Gen[C[T,U]] =
+    sized(s => choose(1,s).flatMap(containerOfN[C,T,U](_,g))) suchThat { c =>
+      c.size > 0 && c.forall(g.sieveCopy)
+    }
 
   /** Generates a list of random length. The maximum length depends on the
    *  size parameter. This method is equal to calling
@@ -482,16 +503,18 @@ object Gen {
 
   /* Generates a string that starts with a lower-case alpha character,
    * and only contains alphanumerical characters */
-  def identifier: Gen[String] = for {
+  def identifier: Gen[String] = (for {
     c <- alphaLowerChar
     cs <- listOf(alphaNumChar)
-  } yield (c::cs).mkString // TODO suchThat
+  } yield (c::cs).mkString).suchThat(_.forall(c => c.isLetter || c.isDigit))
 
   /* Generates a string of alpha characters */
-  def alphaStr: Gen[String] = listOf(alphaChar).map(_.mkString) // TODO suchThat
+  def alphaStr: Gen[String] =
+    listOf(alphaChar).map(_.mkString).suchThat(_.forall(_.isLetter))
 
   /* Generates a string of digits */
-  def numStr: Gen[String] = listOf(numChar).map(_.mkString) // TODO suchThat
+  def numStr: Gen[String] =
+    listOf(numChar).map(_.mkString).suchThat(_.forall(_.isDigit))
 
 
   //// Number Generators ////

src/main/scala/org/scalacheck/util/Buildable.scala

@@ -18,7 +18,6 @@ trait Buildable[T,C[_]] {
     b ++= it
     b.result()
   }
-  // TODO def toIterable
 }
 
 trait Buildable2[T,U,C[_,_]] {

src/test/scala/org/scalacheck/util/BuildableSpecification.scala

@@ -13,8 +13,10 @@ package util
 import collection._
 
 object BuildableSpecification {
-  def container[C[_]](implicit ev: Buildable[String, C]) =
-    Gen.containerOf[C, String](Gen.alphaStr)
+  def container[C[_]](implicit
+    evb: Buildable[String, C],
+    evt: C[String] => Traversable[String]
+  ) = Gen.containerOf[C, String](Gen.alphaStr)
 
   implicit val listGen: Gen[List[String]] = container[List]
 
@@ -41,4 +43,4 @@ object BuildableSpecification {
   implicit val iterableGen: Gen[immutable.Iterable[String]] = container[immutable.Iterable]
 
   implicit val trieIteratorGen: Gen[immutable.Queue[String]] = container[immutable.Queue]
-}
+}