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, 28 insertions, 0 deletions

diff --git a/test/files/pos/depmet_implicit_chaining_zw.scala b/test/files/pos/depmet_implicit_chaining_zw.scala
new file mode 100644
index 0000000000..e3a145ab38
--- /dev/null
+++ b/test/files/pos/depmet_implicit_chaining_zw.scala
@@ -0,0 +1,28 @@
+trait Zero
+trait Succ[N]
+
+trait ZipWith[N, S] {
+  type T
+  val x: T = error("")
+}
+
+object ZipWith {
+  implicit def ZeroZipWith[S] = new ZipWith[Zero, S] {
+    type T = Stream[S]
+  }
+
+  implicit def SuccZipWith[N, S, R](implicit zWith : ZipWith[N, R]) = new ZipWith[Succ[N], S => R] {
+    type T = Stream[S] => zWith.T // dependent types replace the associated types functionality
+  }
+
+  // can't use implicitly[ZipWith[Succ[Succ[Zero]], Int => String => Boolean]],
+  // since that will chop of the {type T = ... } refinement in adapt (pt = ZipWith[Succ[Succ[Zero]], Int => String => Boolean])
+  // this works
+  // def zipWith(implicit zw: ZipWith[Succ[Succ[Zero]], Int => String => Boolean]): zw.T = zw.x
+  // thus, I present ?: implicitly on steroids!
+  def ?[T <: AnyRef](implicit w: T): w.type = w
+
+  type _2 = Succ[Succ[Zero]]
+  val zw = ?[ZipWith[_2, Int => String => Boolean]].x // : Stream[Int] => Stream[String] => Stream[Boolean]
+  // val zw = implicitly[ZipWith[Succ[Succ[Zero]], Int => String => Boolean]{type T = Stream[Int] => Stream[String] => Stream[Boolean]}].x
+}
\ No newline at end of file