Implement alternative desugaring of for-if to filter.

Fallback to .filter if a .withFilter is not available, but do this
only for .withFilter calls generated from for expressions (this is
different from what scalac does; the latter can also rewrite
.withFilter calls given in source, which is not desirable.

1 files changed, 12 insertions, 0 deletions

diff --git a/tests/pos/for-filter.scala b/tests/pos/for-filter.scala
new file mode 100644
index 000000000..3baac4f0c
--- /dev/null
+++ b/tests/pos/for-filter.scala
@@ -0,0 +1,12 @@
+object Test {
+
+  case class C[T](xs: List[T]) {
+    def filter(p: T => Boolean) = new C(xs.filter(p))
+    def map[U](f: T => U) = new C(xs.map(f))
+  }
+
+  def main(args: Array[String]): Unit =
+    println(for (x <- C(List(1, 2, 3)) if x % 2 == 0) yield x)
+    // println(C(List(1, 2, 3)).withFilter(_ % 2 == 0))    // error
+
+}