SI-6187 Make partial functions re-typable

 - `New(tpe)` doesn't survive a `resetAttrs` / typecheck; use
   a name instead.
 - Abandon the tree attachment that passed the default
   case from `typer` to `patmat`; this tree eluded the
   attribute reset performed in the macro. Instead, add it
   to the match. Apart from making the tree re-typable, it
   also exposes the true code structure to macros, which
   is important if they need to perform other code
   transformations.
 - Install original trees on the declared types of the
   parameters of the `applyOrElse` method to ensure that
   references to them within the method pick up the correct
   type parameter skolems upon retypechecking.
 - Propagate `TypeTree#original` through `copyAttrs`,
   which is called during tree duplication / `TreeCopiers`.
   Without this, the original trees that we installed were
   not visible anymore during `ResetAttrs`.

We are not able to reify partial functions yet -- the
particular sticking point is reification of the parentage
which is only available in the `ClassInfoType`.

1 files changed, 28 insertions, 0 deletions

diff --git a/test/pending/run/idempotency-partial-functions.scala b/test/pending/run/idempotency-partial-functions.scala
new file mode 100644
index 0000000000..bc0ca706dd
--- /dev/null
+++ b/test/pending/run/idempotency-partial-functions.scala
@@ -0,0 +1,28 @@
+import scala.reflect.runtime.universe._
+import scala.reflect.runtime.{currentMirror => cm}
+import scala.tools.reflect.{ToolBox, ToolBoxError}
+import scala.tools.reflect.Eval
+
+// Related to SI-6187
+//
+// Moved to pending as we are currently blocked by the inability
+// to reify the parent types of the anoymous function class,
+// which are not part of the tree, but rather only part of the
+// ClassInfoType.
+object Test extends App {
+  val partials = reify {
+    List((false,true)) collect { case (x,true) => x }
+  }
+  println(Seq(show(partials), showRaw(partials)).mkString("\n\n"))
+  try {
+    println(partials.eval)
+  } catch {
+    case e: ToolBoxError => println(e)
+  }
+  val tb = cm.mkToolBox()
+  val tpartials = tb.typeCheck(partials.tree)
+  println(tpartials)
+  val rtpartials = tb.resetAllAttrs(tpartials)
+  println(tb.eval(rtpartials))
+}
+Test.main(null)
\ No newline at end of file