part 2 of the dependent method refactoring: imp...

part 2 of the dependent method refactoring: improved interaction with
implicit search (needed for oopsla paper)

more to come in this area, see e.g. #3346 (stanford edsl stuff)

reopens #13, which wasn't fixed properly before imo, anyway (have a look at -Xprint:typer output before this commit: a type that's not expressible in surface syntax is inferred -- also removed duplicate test file)

closes #3731: co-evolve type alias type symbols when their rhs is
updated and they are referenced by type selections (see typemap)

review by odersky

1 files changed, 44 insertions, 0 deletions

diff --git a/test/files/pos/depmet_implicit_oopsla_zipwith.scala b/test/files/pos/depmet_implicit_oopsla_zipwith.scala
new file mode 100644
index 0000000000..c76d02c1ae
--- /dev/null
+++ b/test/files/pos/depmet_implicit_oopsla_zipwith.scala
@@ -0,0 +1,44 @@
+case class Zero()
+case class Succ[N](x: N)
+import Stream.{cons, continually}
+
+trait ZipWith[N, S] {
+  type T
+
+  def manyApp: N => Stream[S] => T
+  def zipWith: N => S => T = n => f => manyApp(n)(continually(f))
+}
+object ZipWith {
+  implicit def ZeroZipWith[S] = new ZipWith[Zero, S] {
+    type T = Stream[S]
+
+    def manyApp = n => xs => xs
+  }
+
+  implicit def SuccZipWith[N, S, R](implicit zw: ZipWith[N, R]) =
+    new ZipWith[Succ[N],S => R] {
+      type T = Stream[S] => zw.T
+
+      def zapp[A, B](xs: Stream[A => B], ys: Stream[A]): Stream[B] = (xs, ys) match {
+        case (cons(f, fs), cons(s, ss)) => cons(f(s),zapp(fs, ss))
+        case (_, _) => Stream.empty
+      }
+
+      def manyApp = n => xs => ss => n match {
+        case Succ(i) => zw.manyApp(i)(zapp(xs, ss))
+      }
+    }
+}
+
+object Test {
+  def zWith[N, S](n: N, s: S)(implicit zw: ZipWith[N, S]): zw.T = zw.zipWith(n)(s)
+
+  def zipWith0: Stream[Int] = zWith(Zero(),0)
+
+// (Stream[A]) => java.lang.Object with ZipWith[Zero,B]{type T = Stream[B]}#T
+// should normalise to: Stream[A] => Stream[B]
+  def map[A, B](f: A => B) = zWith(Succ(Zero()),f)
+
+  def zipWith3[A, B, C, D](f: A => B => C => D) = //: Stream[A] => Stream[B] => Stream[C] => Stream[D] = // BUG why do we need a return type?
+    zWith(Succ(Succ(Succ(Zero()))),f)
+}
\ No newline at end of file