Collections: remove redundant calls to .seq

Students of Scala's history might recall that at introduction of
parallel collections, GenIterable et al were *not* added; instead
the parallel collections inherited from the existing interfaces.

This of course was an invitation to widespread disaster as any
existing code that foreach-ed over a collection might now experience
unwanted concurrency.

The first attempt to fix this was to add the `.seq` method to
convert a parallel colleciton to a sequential one. This was added
in e579152f732, and call sites in the standard library with
side-effecting foreach calls were changed to use that.

But this was (rightly) deemed inadequate, as we could hardly expect
people to change existing code or remember to do this in new code.

So later, in 3de96153e5b, GenIterable was sprouted, and parallel
collections were re-parented.

This commit removes residual needless calls to .seq when the static
type of the receiver is already a plain Iterable, which are no-ops.

2 files changed, 2 insertions, 2 deletions

diff --git a/src/library/scala/collection/generic/Growable.scala b/src/library/scala/collection/generic/Growable.scala
index 254d4566be..a223c0c8a8 100644
--- a/src/library/scala/collection/generic/Growable.scala
+++ b/src/library/scala/collection/generic/Growable.scala
@@ -54,7 +54,7 @@ trait Growable[-A] extends Clearable {
         loop(xs.tail)
       }
     }
-    xs.seq match {
+    xs match {
       case xs: scala.collection.LinearSeq[_] => loop(xs)
       case xs                                => xs foreach +=
     }
diff --git a/src/library/scala/collection/generic/Shrinkable.scala b/src/library/scala/collection/generic/Shrinkable.scala
index b5ec568667..dea5bb7217 100644
--- a/src/library/scala/collection/generic/Shrinkable.scala
+++ b/src/library/scala/collection/generic/Shrinkable.scala
@@ -46,5 +46,5 @@ trait Shrinkable[-A] {
    *  @param xs   the iterator producing the elements to remove.
    *  @return the $coll itself
    */
-  def --=(xs: TraversableOnce[A]): this.type = { xs.seq foreach -= ; this }
+  def --=(xs: TraversableOnce[A]): this.type = { xs foreach -= ; this }
 }