Spread should always copy arrays.

compiler/backend/src/org/jetbrains/kotlin/codegen/ExpressionCodegen.java

@@ -2683,14 +2683,24 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
         }
 
         if (hasSpread) {
+            boolean arrayOfReferences = KotlinBuiltIns.isArray(outType);
             if (size == 1) {
-                gen(arguments.get(0).getArgumentExpression(), type);
+                // Arrays.copyOf(array, newLength)
+                ValueArgument argument = arguments.get(0);
+                Type arrayType = arrayOfReferences ? Type.getType("[Ljava/lang/Object;")
+                                                   : Type.getType("[" + elementType.getDescriptor());
+                gen(argument.getArgumentExpression(), type);
+                v.dup();
+                v.arraylength();
+                v.invokestatic("java/util/Arrays", "copyOf", Type.getMethodDescriptor(arrayType, arrayType, Type.INT_TYPE), false);
+                if (arrayOfReferences) {
+                    v.checkcast(type);
+                }
             }
             else {
                 String owner;
                 String addDescriptor;
                 String toArrayDescriptor;
-                boolean arrayOfReferences = KotlinBuiltIns.isArray(outType);
                 if (arrayOfReferences) {
                     owner = "kotlin/jvm/internal/SpreadBuilder";
                     addDescriptor = "(Ljava/lang/Object;)V";

compiler/testData/codegen/boxWithStdlib/vararg/spreadCopiesArray.kt

@@ -0,0 +1,27 @@
+import kotlin.test.*
+
+fun <T> copyArray(vararg data: T): Array<out T> = data
+
+inline fun <reified T> reifiedCopyArray(vararg data: T): Array<out T> = data
+
+fun copyIntArray(vararg data: Int): IntArray = data
+
+fun box(): String {
+    val sarr = arrayOf("OK")
+    val sarr2 = copyArray(*sarr)
+    sarr[0] = "Array was not copied"
+    assertEquals(sarr2[0], "OK", "Failed: Array<String>")
+
+    var rsarr = arrayOf("OK")
+    var rsarr2 = reifiedCopyArray(*rsarr)
+    rsarr[0] = "Array was not copied"
+    assertEquals(rsarr2[0], "OK", "Failed: Array<String>, reified copy")
+
+    val iarr = IntArray(1)
+    iarr[0] = 1
+    val iarr2 = copyIntArray(*iarr)
+    iarr[0] = 42
+    assertEquals(iarr2[0], 1, "Failed: IntArray")
+
+    return "OK"
+}

compiler/tests/org/jetbrains/kotlin/codegen/VarArgTest.java

@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.test.ConfigurationKind;
 import java.lang.reflect.Array;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import java.util.Arrays;
 
 public class VarArgTest extends CodegenTestCase {
     @Override
@@ -89,7 +90,9 @@ public class VarArgTest extends CodegenTestCase {
         loadText("private fun asList(vararg elems: String) = elems; fun test(ts: Array<String>) = asList(*ts); ");
         Method main = generateFunction("test");
         String[] args = {"mama", "papa"};
-        assertTrue(args == main.invoke(null, new Object[]{ args } ));
+        String[] result = (String []) main.invoke(null, new Object[] {args});
+        assertTrue(args != result);
+        assertTrue(Arrays.equals(args, result));
     }
 
     public void testArrayAsVararg2() throws InvocationTargetException, IllegalAccessException {

compiler/tests/org/jetbrains/kotlin/codegen/generated/BlackBoxWithStdlibCodegenTestGenerated.java

@@ -4591,6 +4591,12 @@ public class BlackBoxWithStdlibCodegenTestGenerated extends AbstractBlackBoxCode
             JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/codegen/boxWithStdlib/vararg"), Pattern.compile("^(.+)\\.kt$"), true);
         }
 
+        @TestMetadata("spreadCopiesArray.kt")
+        public void testSpreadCopiesArray() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxWithStdlib/vararg/spreadCopiesArray.kt");
+            doTestWithStdlib(fileName);
+        }
+
         @TestMetadata("varargInFunParam.kt")
         public void testVarargInFunParam() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxWithStdlib/vararg/varargInFunParam.kt");