Respect java.lang.Clonable trait and throw exception on clone when it's missing

javalib/src/main/scala/java/util/regex/Matcher.scala

@@ -14,7 +14,8 @@ object Matcher {
 final class Matcher private[regex] (
     var _pattern: Pattern,
     var _inputSequence: CharSequence
-) extends MatchResult {
+) extends MatchResult
+    with Cloneable {
 
   private val underlying = new rMatcher(_pattern.compiled, _inputSequence)
 

nativelib/src/main/scala/java/lang/Object.scala

@@ -59,13 +59,18 @@ class _Object {
     addr.toInt ^ (addr >> 32).toInt
   }
 
-  protected def __clone(): _Object = {
-    val cls = __getClass()
-    val size = cls.size.toUSize
-    val clone = GC.alloc(cls.asInstanceOf[Class[_]], size)
-    val src = castObjectToRawPtr(this)
-    libc.memcpy(clone, src, size)
-    castRawPtrToObject(clone).asInstanceOf[_Object]
+  protected def __clone(): _Object = this match {
+    case _: Cloneable =>
+      val cls = __getClass()
+      val size = cls.size.toUSize
+      val clone = GC.alloc(cls.asInstanceOf[Class[_]], size)
+      val src = castObjectToRawPtr(this)
+      libc.memcpy(clone, src, size)
+      castRawPtrToObject(clone).asInstanceOf[_Object]
+    case _ =>
+      throw new CloneNotSupportedException(
+        "Doesn't implement Cloneable interface!"
+      )
   }
 
   protected def __finalize(): Unit = ()

unit-tests/shared/src/test/scala/org/scalanative/testsuite/javalib/lang/CloneableTest.scala

@@ -0,0 +1,33 @@
+package org.scalanative.testsuite.javalib.lang
+
+import java.lang._
+
+import org.junit.{Ignore, Test}
+import org.junit.Assert._
+
+class CloneableTest {
+
+  class Foo(val x: Int, val y: String) {
+    override def clone(): Foo = super.clone().asInstanceOf[Foo]
+  }
+  class CloneableFoo(val x: Int, val y: String) extends Cloneable() {
+    override def clone(): CloneableFoo =
+      super.clone().asInstanceOf[CloneableFoo]
+  }
+
+  @Test def isNotClonable(): Unit = {
+    assertThrows(
+      classOf[CloneNotSupportedException],
+      () => (new Foo(42, "*").clone())
+    )
+  }
+
+  @Test def isClonable(): Unit = {
+    val instance = new CloneableFoo(42, "*")
+    val clone = instance.clone()
+    assertEquals(instance.getClass(), clone.getClass())
+    assertEquals(instance.x, clone.x)
+    assertEquals(instance.y, clone.y)
+    assertNotSame(instance, clone)
+  }
+}

unit-tests/shared/src/test/scala/scala/ObjectCloneTest.scala

@@ -5,7 +5,7 @@ import org.junit.Assert._
 
 class ObjectCloneTest {
 
-  case class I(var i: Int) {
+  case class I(var i: Int) extends Cloneable {
     def copy(): I = this.clone().asInstanceOf[I]
   }
 
@@ -19,7 +19,7 @@ class ObjectCloneTest {
     assertTrue(clone.i == 123)
   }
 
-  case class Arr(val arr: Array[Int]) {
+  case class Arr(val arr: Array[Int]) extends Cloneable {
     def copy(): Arr = this.clone().asInstanceOf[Arr]
   }