Test usage of SubpatternsAttachment from a macro

Author: densh

test/files/run/macro-subpatterns.check

@@ -0,0 +1,3 @@
+List((a @ Extractor((b @ Extractor((c @ _))))))
+List((b @ Extractor((c @ _))))
+List((c @ _))

test/files/run/macro-subpatterns/Macro_1.scala

@@ -0,0 +1,18 @@
+import scala.reflect.macros.WhiteboxContext
+import language.experimental.macros
+
+object Extractor {
+  def unapply(x: Any): Any = macro unapplyImpl
+  def unapplyImpl(c: WhiteboxContext)(x: c.Tree) = {
+    val st = c.universe.asInstanceOf[reflect.internal.SymbolTable]
+    import st._
+    val subpatterns = x.attachments.get[SubpatternsAttachment].get.patterns
+    q"""
+      new {
+        def isEmpty = false
+        def get = ${subpatterns.toString}
+        def unapply(x: Any) = this
+      }.unapply(${x.asInstanceOf[st.Tree]})
+    """.asInstanceOf[c.Tree]
+  }
+}

test/files/run/macro-subpatterns/Test_2.scala

@@ -0,0 +1,5 @@
+object Test extends App {
+  42 match {
+    case Extractor(a @ Extractor(b @ Extractor(c))) => println(a); println(b); println(c)
+  }
+}