smarter bridges to unapplies

wraps the call to a bridged synthetic unapply(Seq) in a defensive
if-test:

if (x.isInstanceOf[expectedType])
real.unapply(x.asInstanceOf[expectedType]) else None

NOTE: the test is WRONG, but it has to be due to #1697/#2337 -- once those are fixed, this one should generate the expected output

1 files changed, 39 insertions, 0 deletions

diff --git a/test/files/run/patmat_unapp_abstype.scala b/test/files/run/patmat_unapp_abstype.scala
new file mode 100644
index 0000000000..e5adec5c16
--- /dev/null
+++ b/test/files/run/patmat_unapp_abstype.scala
@@ -0,0 +1,39 @@
+// abstract types and extractors, oh my!
+trait TypesAPI {
+  trait Type
+
+  // an alternative fix (implemented in the virtual pattern matcher, is to replace the isInstanceOf by a manifest-based run-time test)
+  // that's what typeRefMani is for
+  type TypeRef <: Type //; implicit def typeRefMani: Manifest[TypeRef]
+  val TypeRef: TypeRefExtractor; trait TypeRefExtractor {
+    def apply(x: Int): TypeRef
+    def unapply(x: TypeRef): Option[(Int)]
+  }
+
+  // just for illustration, should follow the same pattern as TypeRef
+  case class MethodType(n: Int) extends Type
+}
+
+// user should not be exposed to the implementation
+trait TypesUser extends TypesAPI {
+  def shouldNotCrash(tp: Type): Unit = {
+    tp match {
+      case TypeRef(x) => println("TypeRef") 
+      case MethodType(x) => println("MethodType")
+      case _ => println("none of the above")
+    }
+  }
+}
+
+trait TypesImpl extends TypesAPI {
+  object TypeRef extends TypeRefExtractor  // this will have a bridged unapply(x: Type) = unapply(x.asInstanceOf[TypeRef])
+  case class TypeRef(n: Int) extends Type // this has a bridge from TypesAPI#Type to TypesImpl#TypeRef 
+  // --> the cast in the bridge will fail because the pattern matcher can't type test against the abstract types in TypesUser
+  //lazy val typeRefMani = manifest[TypeRef]
+}
+
+object Test extends TypesImpl with TypesUser with App {
+  shouldNotCrash(TypeRef(10)) // should and does print "TypeRef"
+  // once  #1697/#2337 are fixed, this should generate the correct output
+  shouldNotCrash(MethodType(10)) // should print "MethodType" but prints "none of the above" -- good one, pattern matcher!
+}
\ No newline at end of file