SI-5903 extractor macros do work

Apparently it is already possible to use macros to customize pattern
matching as described in the comments to the aforementioned JIRA issue.

What's even better - with the incoming addition of c.introduceTopLevel
it becomes possible to generate arbitrarily complex unappliers, even
with heterogeneous types of arguments varying from expansion to expansion

8 files changed, 72 insertions, 0 deletions

diff --git a/test/files/run/macro-expand-unapply-a.check b/test/files/run/macro-expand-unapply-a.check
new file mode 100644
index 0000000000..7c2976e51e
--- /dev/null
+++ b/test/files/run/macro-expand-unapply-a.check
@@ -0,0 +1,2 @@
+(1,2)
+(1,2,3)
diff --git a/test/files/run/macro-expand-unapply-a.flags b/test/files/run/macro-expand-unapply-a.flags
new file mode 100644
index 0000000000..cd66464f2f
--- /dev/null
+++ b/test/files/run/macro-expand-unapply-a.flags
@@ -0,0 +1 @@
+-language:experimental.macros
\ No newline at end of file
diff --git a/test/files/run/macro-expand-unapply-a/Impls_Macros_1.scala b/test/files/run/macro-expand-unapply-a/Impls_Macros_1.scala
new file mode 100644
index 0000000000..61d6345f16
--- /dev/null
+++ b/test/files/run/macro-expand-unapply-a/Impls_Macros_1.scala
@@ -0,0 +1,15 @@
+import scala.reflect.macros.Context
+
+object Helper {
+  def unapplySeq[T](x: List[T]): Option[Seq[T]] = List.unapplySeq[T](x)
+}
+
+object Macros {
+  def impl[T: c.WeakTypeTag](c: Context)(x: c.Expr[List[T]]) = {
+    c.universe.reify(Helper.unapplySeq(x.splice))
+  }
+
+  object UnapplyMacro {
+    def unapplySeq[T](x: List[T]): Option[Seq[T]] = macro impl[T]
+  }
+}
\ No newline at end of file
diff --git a/test/files/run/macro-expand-unapply-a/Test_2.scala b/test/files/run/macro-expand-unapply-a/Test_2.scala
new file mode 100644
index 0000000000..6169d86b19
--- /dev/null
+++ b/test/files/run/macro-expand-unapply-a/Test_2.scala
@@ -0,0 +1,6 @@
+import Macros._
+
+object Test extends App {
+  List(1, 2) match { case UnapplyMacro(x, y) => println((x, y)) }
+  List(1, 2, 3) match { case UnapplyMacro(x, y, z) => println((x, y, z)) }
+}
\ No newline at end of file
diff --git a/test/files/run/macro-expand-unapply-b.check b/test/files/run/macro-expand-unapply-b.check
new file mode 100644
index 0000000000..5272f0d00a
--- /dev/null
+++ b/test/files/run/macro-expand-unapply-b.check
@@ -0,0 +1,2 @@
+(1,List(2))
+List(1)
diff --git a/test/files/run/macro-expand-unapply-b.flags b/test/files/run/macro-expand-unapply-b.flags
new file mode 100644
index 0000000000..cd66464f2f
--- /dev/null
+++ b/test/files/run/macro-expand-unapply-b.flags
@@ -0,0 +1 @@
+-language:experimental.macros
\ No newline at end of file
diff --git a/test/files/run/macro-expand-unapply-b/Impls_Macros_1.scala b/test/files/run/macro-expand-unapply-b/Impls_Macros_1.scala
new file mode 100644
index 0000000000..d0300bdf7e
--- /dev/null
+++ b/test/files/run/macro-expand-unapply-b/Impls_Macros_1.scala
@@ -0,0 +1,37 @@
+import language.experimental.macros
+import scala.reflect.macros.Context
+
+object Macros {
+  implicit class ContextExtensions(c: StringContext) {
+    object q {
+      def unapply(x: Any): Option[Any] = macro impl
+    }
+  }
+
+  def impl(c: Context)(x: c.Expr[Any]): c.Expr[Option[Any]] = {
+    import c.universe._
+    import Flag._
+
+    // parts here will be string literals - static parts of the string interpolation
+    // e.g. for q"$x, $y" parts will be Literal(Constant("")), Literal(Constant(", ")) and Literal(Constant(""))
+    val Apply(Select(Select(Apply(_, List(Apply(_, parts))), _), _), _) = c.macroApplication
+    val nresults = parts.length - 1
+
+    def results() =
+      ((1 to (nresults - 1)).toList map (i => Literal(Constant(i)))) :+  // (n - 1) results of type Int
+      Apply(Ident(TermName("List")), List(Literal(Constant(nresults))))  // and also one result of a different type
+    def extractorBody() =
+      if (nresults == 0) Literal(Constant(true))
+      else if (nresults == 1) Apply(Ident(TermName("Some")), results())
+      else Apply(Ident(TermName("Some")), List(Apply(Ident(TermName("Tuple" + nresults)), results())))
+
+    val name = TermName(java.util.UUID.randomUUID().toString.replace("-", ""))
+    val mdef = ModuleDef(NoMods, name, Template(List(Select(Ident(TermName("scala")), TypeName("AnyRef"))), emptyValDef, List(
+      DefDef(Modifiers(), nme.CONSTRUCTOR, List(), List(List()), TypeTree(),
+        Block(List(pendingSuperCall), Literal(Constant(())))),
+      DefDef(Modifiers(), TermName("unapply"), List(), List(List(ValDef(Modifiers(PARAM), TermName("x"), Ident(TypeName("Any")), EmptyTree))), TypeTree(),
+        extractorBody()))))
+    c.introduceTopLevel(nme.EMPTY_PACKAGE_NAME.toString, mdef)
+    c.Expr[Option[Any]](Apply(Select(Ident(name), TermName("unapply")), List(x.tree)))
+  }
+}
\ No newline at end of file
diff --git a/test/files/run/macro-expand-unapply-b/Test_2.scala b/test/files/run/macro-expand-unapply-b/Test_2.scala
new file mode 100644
index 0000000000..5352160dfe
--- /dev/null
+++ b/test/files/run/macro-expand-unapply-b/Test_2.scala
@@ -0,0 +1,8 @@
+object Test extends App {
+  import Macros._
+  def whatever() = null
+  val q"$x1, $y1" = whatever()
+  println(x1, y1)
+  val q"$x2" = whatever()
+  println(x2)
+}