Merge pull request #324 from pbatko/null-isas-instanceof

Fix null.isInstanceOf

tools/src/main/scala/scala/scalanative/compiler/pass/IsLowering.scala

@@ -8,7 +8,44 @@ import nir._, Inst.Let
 
 /** Translates instance checks to range checks on type ids. */
 class IsLowering(implicit fresh: Fresh, top: Top) extends Pass {
-  override def preInst = {
+
+  override def preInst = eliminateIs
+
+  private def eliminateIs: PartialFunction[Inst, Seq[Inst]] = {
+    case Let(n, Op.Is(_, Val.Zero(_))) =>
+      Seq(Let(n, Op.Copy(Val.False)))
+
+    case isInst @ Let(n, Op.Is(ty, obj)) =>
+      val isNullV = Val.Local(fresh(), Type.Bool)
+      val isIsV   = Val.Local(fresh(), Type.Bool)
+
+      val thenL = fresh()
+      val elseL = fresh()
+      val contL = fresh()
+
+      val thenResultV = Val.Local(fresh(), Type.Bool)
+      val elseResultV = Val.Local(fresh(), Type.Bool)
+
+      Seq(
+          // if
+          Let(isNullV.name,
+              Op.Comp(Comp.Ieq, Type.Ptr, obj, Val.Zero(Type.Ptr))),
+          Inst.If(isNullV, Next(thenL), Next(elseL)),
+          // then
+          Inst.Label(thenL, Seq.empty),
+          Let(thenResultV.name, Op.Copy(Val.False)),
+          Inst.Jump(Next.Label(contL, Seq(thenResultV))),
+          // else
+          Inst.Label(elseL, Seq.empty)) ++
+      doEliminateIs(Let(elseResultV.name, Op.Is(ty, obj))) ++
+      Seq(Inst.Jump(Next.Label(contL, Seq(elseResultV))),
+          // cont
+          Inst.Label(contL, Seq(isIsV)),
+          Let(n, Op.Copy(isIsV)))
+    case other => Seq(other)
+  }
+
+  private def doEliminateIs: PartialFunction[Inst, Seq[Inst]] = {
     case Let(n, Op.Is(ClassRef(cls), obj)) if cls.range.length == 1 =>
       val typeptr = Val.Local(fresh(), Type.Ptr)
 
@@ -53,6 +90,7 @@ class IsLowering(implicit fresh: Fresh, top: Top) extends Pass {
                       Seq(Val.I32(0), id, Val.I32(trt.id)))),
           Let(n, Op.Load(Type.Bool, boolptr))
       )
+    case other => Seq(other)
   }
 }
 

unit-tests/src/main/scala/scala/scalanative/native/InstanceOfSuite.scala

@@ -0,0 +1,79 @@
+package scala.scalanative.native
+
+object InstanceOfSuite extends tests.Suite {
+
+  // asInstanceOf
+
+//  test("expects anyRef.asInstanceOf[String] fail") {
+//    shouldNotGetHere((new AnyRef).asInstanceOf[String])
+//  }
+
+  test("expects \"\".asInstanceOf[String] succeed") {
+    assertNotNull("".asInstanceOf[String])
+  }
+
+  test("expects null.asInstanceOf[String] should succeed") {
+    assertNull(null.asInstanceOf[String])
+  }
+
+  test("expects a.asInstanceOf[String], where a = null should succeed") {
+    castNullToString(null)
+  }
+
+  def castNullToString(x: AnyRef): Unit = {
+    if (x.isInstanceOf[String]) {
+      assertNull(x.asInstanceOf[String])
+    }
+
+  }
+
+  def assertNull(s: String): Unit = {
+    assert(s == null)
+  }
+
+  def assertNotNull(s: String): Unit = {
+    assert(s != null)
+  }
+
+  def shouldNotGetHere(s: String): Unit = {
+    assert(false)
+  }
+
+  // isInstanceOf
+
+  test("expects (new AnyRef).asInstanceOf[AnyRef] should succeeds") {
+    (new AnyRef).asInstanceOf[AnyRef]
+  }
+
+  test("expects anyRef.isInstanceOf[String] == false") {
+    val anyRef = new AnyRef
+    assert(!anyRef.isInstanceOf[String])
+  }
+
+  test("expects literal null.isInstanceOf[String] == false") {
+    assert(!null.isInstanceOf[String])
+  }
+
+  test("expects \"\".isInstanceOf[String] == true") {
+    assert("".isInstanceOf[String])
+  }
+
+  test("expects a.isInstanceOf[String] == true, where a = \"\"") {
+    assertIsInstanceOfString("", "")
+  }
+
+  test("expects a.isInstanceOf[String] == false, where a = null") {
+    assertNullIsNotInstanceOfString(null, null)
+  }
+
+  def assertNullIsNotInstanceOfString(a: AnyRef, b: AnyRef): Unit = {
+    assert(!a.isInstanceOf[String])
+    assert(!b.isInstanceOf[String])
+  }
+
+  def assertIsInstanceOfString(a: AnyRef, b: AnyRef): Unit = {
+    assert(a.isInstanceOf[String])
+    assert(b.isInstanceOf[String])
+  }
+
+}

unit-tests/src/main/scala/tests/Main.scala

@@ -12,6 +12,7 @@ object Main {
       scala.scalanative.issues._337,
       scala.scalanative.native.CStringSuite,
       scala.scalanative.native.CInteropSuite,
+      scala.scalanative.native.InstanceOfSuite,
       scala.ArrayIntCopySuite,
       scala.ArrayDoubleCopySuite,
       scala.ArrayObjectCopySuite