8155106: MHs.Lookup.findConstructor returns handles for array classes

Reviewed-by: shade, sundar

jdk/src/java.base/share/classes/java/lang/invoke/MethodHandleImpl.java

@@ -25,6 +25,7 @@
 
 package java.lang.invoke;
 
+import java.lang.reflect.Array;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.util.Arrays;
@@ -1892,7 +1893,8 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
             MH_tryFinallyExec        = 12,
             MH_tryFinallyVoidExec    = 13,
             MH_decrementCounter      = 14,
-            MH_LIMIT                 = 15;
+            MH_Array_newInstance     = 15,
+            MH_LIMIT                 = 16;
 
     static MethodHandle getConstantHandle(int idx) {
         MethodHandle handle = HANDLES[idx];
@@ -1965,6 +1967,9 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
                 case MH_decrementCounter:
                     return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "decrementCounter",
                             MethodType.methodType(int.class, int.class));
+                case MH_Array_newInstance:
+                    return IMPL_LOOKUP.findStatic(Array.class, "newInstance",
+                            MethodType.methodType(Object.class, Class.class, int.class));
             }
         } catch (ReflectiveOperationException ex) {
             throw newInternalError(ex);

jdk/src/java.base/share/classes/java/lang/invoke/MethodHandles.java

@@ -1010,6 +1010,9 @@ assertEquals("[x, y, z]", pb.command().toString());
          * @throws NullPointerException if any argument is null
          */
         public MethodHandle findConstructor(Class<?> refc, MethodType type) throws NoSuchMethodException, IllegalAccessException {
+            if (refc.isArray()) {
+                throw new NoSuchMethodException("no constructor for array class: " + refc.getName());
+            }
             String name = "<init>";
             MemberName ctor = resolveOrFail(REF_newInvokeSpecial, refc, name, type);
             return getDirectConstructor(refc, ctor);
@@ -2220,6 +2223,27 @@ return mh1;
         static final Lookup PUBLIC_LOOKUP = new Lookup(PUBLIC_LOOKUP_CLASS, Lookup.PUBLIC);
     }
 
+    /**
+     * Produces a method handle constructing arrays of a desired type.
+     * The return type of the method handle will be the array type.
+     * The type of its sole argument will be {@code int}, which specifies the size of the array.
+     * @param arrayClass an array type
+     * @return a method handle which can create arrays of the given type
+     * @throws NullPointerException if the argument is {@code null}
+     * @throws IllegalArgumentException if {@code arrayClass} is not an array type
+     * @see java.lang.reflect.Array#newInstance(Class, int)
+     * @since 9
+     */
+    public static
+    MethodHandle arrayConstructor(Class<?> arrayClass) throws IllegalArgumentException {
+        if (!arrayClass.isArray()) {
+            throw newIllegalArgumentException("not an array class: " + arrayClass.getName());
+        }
+        MethodHandle ani = MethodHandleImpl.getConstantHandle(MethodHandleImpl.MH_Array_newInstance).
+                bindTo(arrayClass.getComponentType());
+        return ani.asType(ani.type().changeReturnType(arrayClass));
+    }
+
     /**
      * Produces a method handle giving read access to elements of an array.
      * The type of the method handle will have a return type of the array's

jdk/test/java/lang/invoke/ArrayConstructorTest.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/* @test
+ * @bug 8155106
+ * @run testng/othervm -ea -esa test.java.lang.invoke.ArrayConstructorTest
+ */
+package test.java.lang.invoke;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+
+import static java.lang.invoke.MethodType.methodType;
+
+import static org.testng.AssertJUnit.*;
+
+import org.testng.annotations.*;
+
+
+public class ArrayConstructorTest {
+
+    static final MethodHandles.Lookup LOOKUP = MethodHandles.lookup();
+
+    @Test
+    public static void testFindConstructorArray() {
+        boolean caught = false;
+        try {
+            MethodHandle h = LOOKUP.findConstructor(Object[].class, methodType(void.class));
+        } catch (NoSuchMethodException nsme) {
+            assertEquals("no constructor for array class: [Ljava.lang.Object;", nsme.getMessage());
+            caught = true;
+        } catch (Exception e) {
+            throw new AssertionError("unexpected exception: " + e);
+        }
+        assertTrue(caught);
+    }
+
+    @DataProvider
+    static Object[][] arrayConstructorNegative() {
+        return new Object[][]{
+                {String.class, IllegalArgumentException.class, "not an array class: java.lang.String"},
+                {null, NullPointerException.class, null}
+        };
+    }
+
+    @Test(dataProvider = "arrayConstructorNegative")
+    public static void testArrayConstructorNegative(Class<?> clazz, Class<?> exceptionClass, String message) {
+        boolean caught = false;
+        try {
+            MethodHandle h = MethodHandles.arrayConstructor(clazz);
+        } catch (Exception e) {
+            assertEquals(exceptionClass, e.getClass());
+            if (message != null) {
+                assertEquals(message, e.getMessage());
+            }
+            caught = true;
+        }
+        assertTrue(caught);
+    }
+
+    @Test
+    public static void testArrayConstructor() throws Throwable {
+        MethodHandle h = MethodHandles.arrayConstructor(String[].class);
+        assertEquals(methodType(String[].class, int.class), h.type());
+        String[] a = (String[]) h.invoke(17);
+        assertEquals(17, a.length);
+    }
+
+}