Bootstrap.java revision 1197:20c3aef2b4cb
1/* 2 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26package jdk.nashorn.internal.runtime.linker; 27 28import static jdk.nashorn.internal.codegen.CompilerConstants.staticCallNoLookup; 29import static jdk.nashorn.internal.runtime.ECMAErrors.typeError; 30 31import java.lang.invoke.CallSite; 32import java.lang.invoke.ConstantCallSite; 33import java.lang.invoke.MethodHandle; 34import java.lang.invoke.MethodHandles; 35import java.lang.invoke.MethodHandles.Lookup; 36import java.lang.invoke.MethodType; 37import jdk.internal.dynalink.CallSiteDescriptor; 38import jdk.internal.dynalink.DynamicLinker; 39import jdk.internal.dynalink.DynamicLinkerFactory; 40import jdk.internal.dynalink.GuardedInvocationFilter; 41import jdk.internal.dynalink.beans.BeansLinker; 42import jdk.internal.dynalink.beans.StaticClass; 43import jdk.internal.dynalink.linker.GuardedInvocation; 44import jdk.internal.dynalink.linker.LinkRequest; 45import jdk.internal.dynalink.linker.LinkerServices; 46import jdk.internal.dynalink.linker.MethodTypeConversionStrategy; 47import jdk.internal.dynalink.support.TypeUtilities; 48import jdk.nashorn.api.scripting.JSObject; 49import jdk.nashorn.internal.codegen.CompilerConstants.Call; 50import jdk.nashorn.internal.codegen.ObjectClassGenerator; 51import jdk.nashorn.internal.lookup.MethodHandleFactory; 52import jdk.nashorn.internal.lookup.MethodHandleFunctionality; 53import jdk.nashorn.internal.objects.ScriptFunctionImpl; 54import jdk.nashorn.internal.runtime.ECMAException; 55import jdk.nashorn.internal.runtime.JSType; 56import jdk.nashorn.internal.runtime.OptimisticReturnFilters; 57import jdk.nashorn.internal.runtime.ScriptFunction; 58import jdk.nashorn.internal.runtime.ScriptRuntime; 59import jdk.nashorn.internal.runtime.options.Options; 60 61/** 62 * This class houses bootstrap method for invokedynamic instructions generated by compiler. 63 */ 64public final class Bootstrap { 65 /** Reference to the seed boostrap function */ 66 public static final Call BOOTSTRAP = staticCallNoLookup(Bootstrap.class, "bootstrap", CallSite.class, Lookup.class, String.class, MethodType.class, int.class); 67 68 private static final MethodHandleFunctionality MH = MethodHandleFactory.getFunctionality(); 69 70 private static final MethodHandle VOID_TO_OBJECT = MH.constant(Object.class, ScriptRuntime.UNDEFINED); 71 72 /** 73 * The default dynalink relink threshold for megamorphisism is 8. In the case 74 * of object fields only, it is fine. However, with dual fields, in order to get 75 * performance on benchmarks with a lot of object instantiation and then field 76 * reassignment, it can take slightly more relinks to become stable with type 77 * changes swapping out an entire proprety map and making a map guard fail. 78 * Therefore the relink threshold is set to 16 for dual fields (now the default). 79 * This doesn't seem to have any other negative performance implication. 80 * 81 * See for example octane.gbemu, run with --log=fields:warning to study 82 * megamorphic behavior 83 */ 84 private static final int NASHORN_DEFAULT_UNSTABLE_RELINK_THRESHOLD = 85 ObjectClassGenerator.OBJECT_FIELDS_ONLY ? 86 8 : 87 16; 88 89 // do not create me!! 90 private Bootstrap() { 91 } 92 93 private static final DynamicLinker dynamicLinker; 94 static { 95 final DynamicLinkerFactory factory = new DynamicLinkerFactory(); 96 final NashornBeansLinker nashornBeansLinker = new NashornBeansLinker(); 97 factory.setPrioritizedLinkers( 98 new NashornLinker(), 99 new NashornPrimitiveLinker(), 100 new NashornStaticClassLinker(), 101 new BoundCallableLinker(), 102 new JavaSuperAdapterLinker(), 103 new JSObjectLinker(nashornBeansLinker), 104 new BrowserJSObjectLinker(nashornBeansLinker), 105 new ReflectionCheckLinker()); 106 factory.setFallbackLinkers(nashornBeansLinker, new NashornBottomLinker()); 107 factory.setSyncOnRelink(true); 108 factory.setPrelinkFilter(new GuardedInvocationFilter() { 109 @Override 110 public GuardedInvocation filter(final GuardedInvocation inv, final LinkRequest request, final LinkerServices linkerServices) { 111 final CallSiteDescriptor desc = request.getCallSiteDescriptor(); 112 return OptimisticReturnFilters.filterOptimisticReturnValue(inv, desc).asType(linkerServices, desc.getMethodType()); 113 } 114 }); 115 factory.setAutoConversionStrategy(new MethodTypeConversionStrategy() { 116 @Override 117 public MethodHandle asType(final MethodHandle target, final MethodType newType) { 118 return unboxReturnType(target, newType); 119 } 120 }); 121 factory.setInternalObjectsFilter(NashornBeansLinker.createHiddenObjectFilter()); 122 final int relinkThreshold = Options.getIntProperty("nashorn.unstable.relink.threshold", NASHORN_DEFAULT_UNSTABLE_RELINK_THRESHOLD); 123 if (relinkThreshold > -1) { 124 factory.setUnstableRelinkThreshold(relinkThreshold); 125 } 126 127 // Linkers for any additional language runtimes deployed alongside Nashorn will be picked up by the factory. 128 factory.setClassLoader(Bootstrap.class.getClassLoader()); 129 130 dynamicLinker = factory.createLinker(); 131 } 132 133 /** 134 * Returns if the given object is a "callable" 135 * @param obj object to be checked for callability 136 * @return true if the obj is callable 137 */ 138 public static boolean isCallable(final Object obj) { 139 if (obj == ScriptRuntime.UNDEFINED || obj == null) { 140 return false; 141 } 142 143 return obj instanceof ScriptFunction || 144 isJSObjectFunction(obj) || 145 BeansLinker.isDynamicMethod(obj) || 146 obj instanceof BoundCallable || 147 isFunctionalInterfaceObject(obj) || 148 obj instanceof StaticClass; 149 } 150 151 /** 152 * Returns true if the given object is a strict callable 153 * @param callable the callable object to be checked for strictness 154 * @return true if the obj is a strict callable, false if it is a non-strict callable. 155 * @throws ECMAException with {@code TypeError} if the object is not a callable. 156 */ 157 public static boolean isStrictCallable(final Object callable) { 158 if (callable instanceof ScriptFunction) { 159 return ((ScriptFunction)callable).isStrict(); 160 } else if (isJSObjectFunction(callable)) { 161 return ((JSObject)callable).isStrictFunction(); 162 } else if (callable instanceof BoundCallable) { 163 return isStrictCallable(((BoundCallable)callable).getCallable()); 164 } else if (BeansLinker.isDynamicMethod(callable) || callable instanceof StaticClass) { 165 return false; 166 } 167 throw notFunction(callable); 168 } 169 170 private static ECMAException notFunction(final Object obj) { 171 return typeError("not.a.function", ScriptRuntime.safeToString(obj)); 172 } 173 174 private static boolean isJSObjectFunction(final Object obj) { 175 return obj instanceof JSObject && ((JSObject)obj).isFunction(); 176 } 177 178 /** 179 * Returns if the given object is a dynalink Dynamic method 180 * @param obj object to be checked 181 * @return true if the obj is a dynamic method 182 */ 183 public static boolean isDynamicMethod(final Object obj) { 184 return BeansLinker.isDynamicMethod(obj instanceof BoundCallable ? ((BoundCallable)obj).getCallable() : obj); 185 } 186 187 /** 188 * Returns if the given object is an instance of an interface annotated with 189 * java.lang.FunctionalInterface 190 * @param obj object to be checked 191 * @return true if the obj is an instance of @FunctionalInterface interface 192 */ 193 public static boolean isFunctionalInterfaceObject(final Object obj) { 194 return !JSType.isPrimitive(obj) && (NashornBeansLinker.getFunctionalInterfaceMethod(obj.getClass()) != null); 195 } 196 197 /** 198 * Create a call site and link it for Nashorn. This version of the method conforms to the invokedynamic bootstrap 199 * method expected signature and is referenced from Nashorn generated bytecode as the bootstrap method for all 200 * invokedynamic instructions. 201 * @param lookup MethodHandle lookup. Ignored as Nashorn only uses public lookup. 202 * @param opDesc Dynalink dynamic operation descriptor. 203 * @param type Method type. 204 * @param flags flags for call type, trace/profile etc. 205 * @return CallSite with MethodHandle to appropriate method or null if not found. 206 */ 207 public static CallSite bootstrap(final Lookup lookup, final String opDesc, final MethodType type, final int flags) { 208 return dynamicLinker.link(LinkerCallSite.newLinkerCallSite(lookup, opDesc, type, flags)); 209 } 210 211 /** 212 * Boostrapper for math calls that may overflow 213 * @param lookup lookup 214 * @param name name of operation 215 * @param type method type 216 * @param programPoint program point to bind to callsite 217 * 218 * @return callsite for a math instrinic node 219 */ 220 public static CallSite mathBootstrap(final MethodHandles.Lookup lookup, final String name, final MethodType type, final int programPoint) { 221 final MethodHandle mh; 222 switch (name) { 223 case "iadd": 224 mh = JSType.ADD_EXACT.methodHandle(); 225 break; 226 case "isub": 227 mh = JSType.SUB_EXACT.methodHandle(); 228 break; 229 case "imul": 230 mh = JSType.MUL_EXACT.methodHandle(); 231 break; 232 case "idiv": 233 mh = JSType.DIV_EXACT.methodHandle(); 234 break; 235 case "irem": 236 mh = JSType.REM_EXACT.methodHandle(); 237 break; 238 case "ineg": 239 mh = JSType.NEGATE_EXACT.methodHandle(); 240 break; 241 case "ladd": 242 mh = JSType.ADD_EXACT_LONG.methodHandle(); 243 break; 244 case "lsub": 245 mh = JSType.SUB_EXACT_LONG.methodHandle(); 246 break; 247 case "lmul": 248 mh = JSType.MUL_EXACT_LONG.methodHandle(); 249 break; 250 case "ldiv": 251 mh = JSType.DIV_EXACT_LONG.methodHandle(); 252 break; 253 case "lrem": 254 mh = JSType.REM_EXACT_LONG.methodHandle(); 255 break; 256 case "lneg": 257 mh = JSType.NEGATE_EXACT_LONG.methodHandle(); 258 break; 259 default: 260 throw new AssertionError("unsupported math intrinsic"); 261 } 262 return new ConstantCallSite(MH.insertArguments(mh, mh.type().parameterCount() - 1, programPoint)); 263 } 264 265 /** 266 * Returns a dynamic invoker for a specified dynamic operation using the public lookup. You can use this method to 267 * create a method handle that when invoked acts completely as if it were a Nashorn-linked call site. An overview of 268 * available dynamic operations can be found in the 269 * <a href="https://github.com/szegedi/dynalink/wiki/User-Guide-0.6">Dynalink User Guide</a>, but we'll show few 270 * examples here: 271 * <ul> 272 * <li>Get a named property with fixed name: 273 * <pre> 274 * MethodHandle getColor = Boostrap.createDynamicInvoker("dyn:getProp:color", Object.class, Object.class); 275 * Object obj = ...; // somehow obtain the object 276 * Object color = getColor.invokeExact(obj); 277 * </pre> 278 * </li> 279 * <li>Get a named property with variable name: 280 * <pre> 281 * MethodHandle getProperty = Boostrap.createDynamicInvoker("dyn:getElem", Object.class, Object.class, String.class); 282 * Object obj = ...; // somehow obtain the object 283 * Object color = getProperty.invokeExact(obj, "color"); 284 * Object shape = getProperty.invokeExact(obj, "shape"); 285 * MethodHandle getNumProperty = Boostrap.createDynamicInvoker("dyn:getElem", Object.class, Object.class, int.class); 286 * Object elem42 = getNumProperty.invokeExact(obj, 42); 287 * </pre> 288 * </li> 289 * <li>Set a named property with fixed name: 290 * <pre> 291 * MethodHandle setColor = Boostrap.createDynamicInvoker("dyn:setProp:color", void.class, Object.class, Object.class); 292 * Object obj = ...; // somehow obtain the object 293 * setColor.invokeExact(obj, Color.BLUE); 294 * </pre> 295 * </li> 296 * <li>Set a property with variable name: 297 * <pre> 298 * MethodHandle setProperty = Boostrap.createDynamicInvoker("dyn:setElem", void.class, Object.class, String.class, Object.class); 299 * Object obj = ...; // somehow obtain the object 300 * setProperty.invokeExact(obj, "color", Color.BLUE); 301 * setProperty.invokeExact(obj, "shape", Shape.CIRCLE); 302 * </pre> 303 * </li> 304 * <li>Call a function on an object; two-step variant. This is the actual variant used by Nashorn-generated code: 305 * <pre> 306 * MethodHandle findFooFunction = Boostrap.createDynamicInvoker("dyn:getMethod:foo", Object.class, Object.class); 307 * Object obj = ...; // somehow obtain the object 308 * Object foo_fn = findFooFunction.invokeExact(obj); 309 * MethodHandle callFunctionWithTwoArgs = Boostrap.createDynamicInvoker("dyn:call", Object.class, Object.class, Object.class, Object.class, Object.class); 310 * // Note: "call" operation takes a function, then a "this" value, then the arguments: 311 * Object foo_retval = callFunctionWithTwoArgs.invokeExact(foo_fn, obj, arg1, arg2); 312 * </pre> 313 * </li> 314 * <li>Call a function on an object; single-step variant. Although Nashorn doesn't use this variant and never 315 * emits any INVOKEDYNAMIC instructions with {@code dyn:getMethod}, it still supports this standard Dynalink 316 * operation: 317 * <pre> 318 * MethodHandle callFunctionFooWithTwoArgs = Boostrap.createDynamicInvoker("dyn:callMethod:foo", Object.class, Object.class, Object.class, Object.class); 319 * Object obj = ...; // somehow obtain the object 320 * Object foo_retval = callFunctionFooWithTwoArgs.invokeExact(obj, arg1, arg2); 321 * </pre> 322 * </li> 323 * </ul> 324 * Few additional remarks: 325 * <ul> 326 * <li>Just as Nashorn works with any Java object, the invokers returned from this method can also be applied to 327 * arbitrary Java objects in addition to Nashorn JavaScript objects.</li> 328 * <li>For invoking a named function on an object, you can also use the {@link InvokeByName} convenience class.</li> 329 * <li>For Nashorn objects {@code getElem}, {@code getProp}, and {@code getMethod} are handled almost identically, 330 * since JavaScript doesn't distinguish between different kinds of properties on an object. Either can be used with 331 * fixed property name or a variable property name. The only significant difference is handling of missing 332 * properties: {@code getMethod} for a missing member will link to a potential invocation of 333 * {@code __noSuchMethod__} on the object, {@code getProp} for a missing member will link to a potential invocation 334 * of {@code __noSuchProperty__}, while {@code getElem} for a missing member will link to an empty getter.</li> 335 * <li>In similar vein, {@code setElem} and {@code setProp} are handled identically on Nashorn objects.</li> 336 * <li>There's no rule that the variable property identifier has to be a {@code String} for {@code getProp/setProp} 337 * and {@code int} for {@code getElem/setElem}. You can declare their type to be {@code int}, {@code double}, 338 * {@code Object}, and so on regardless of the kind of the operation.</li> 339 * <li>You can be as specific in parameter types as you want. E.g. if you know that the receiver of the operation 340 * will always be {@code ScriptObject}, you can pass {@code ScriptObject.class} as its parameter type. If you happen 341 * to link to a method that expects different types, (you can use these invokers on POJOs too, after all, and end up 342 * linking with their methods that have strongly-typed signatures), all necessary conversions allowed by either Java 343 * or JavaScript will be applied: if invoked methods specify either primitive or wrapped Java numeric types, or 344 * {@code String} or {@code boolean/Boolean}, then the parameters might be subjected to standard ECMAScript 345 * {@code ToNumber}, {@code ToString}, and {@code ToBoolean} conversion, respectively. Less obviously, if the 346 * expected parameter type is a SAM type, and you pass a JavaScript function, a proxy object implementing the SAM 347 * type and delegating to the function will be passed. Linkage can often be optimized when linkers have more 348 * specific type information than "everything can be an object".</li> 349 * <li>You can also be as specific in return types as you want. For return types any necessary type conversion 350 * available in either Java or JavaScript will be automatically applied, similar to the process described for 351 * parameters, only in reverse direction: if you specify any either primitive or wrapped Java numeric type, or 352 * {@code String} or {@code boolean/Boolean}, then the return values will be subjected to standard ECMAScript 353 * {@code ToNumber}, {@code ToString}, and {@code ToBoolean} conversion, respectively. Less obviously, if the return 354 * type is a SAM type, and the return value is a JavaScript function, a proxy object implementing the SAM type and 355 * delegating to the function will be returned.</li> 356 * </ul> 357 * @param opDesc Dynalink dynamic operation descriptor. 358 * @param rtype the return type for the operation 359 * @param ptypes the parameter types for the operation 360 * @return MethodHandle for invoking the operation. 361 */ 362 public static MethodHandle createDynamicInvoker(final String opDesc, final Class<?> rtype, final Class<?>... ptypes) { 363 return createDynamicInvoker(opDesc, MethodType.methodType(rtype, ptypes)); 364 } 365 366 /** 367 * Returns a dynamic invoker for a specified dynamic operation using the public lookup. Similar to 368 * {@link #createDynamicInvoker(String, Class, Class...)} but with an additional parameter to 369 * set the call site flags of the dynamic invoker. 370 * @param opDesc Dynalink dynamic operation descriptor. 371 * @param flags the call site flags for the operation 372 * @param rtype the return type for the operation 373 * @param ptypes the parameter types for the operation 374 * @return MethodHandle for invoking the operation. 375 */ 376 public static MethodHandle createDynamicInvoker(final String opDesc, final int flags, final Class<?> rtype, final Class<?>... ptypes) { 377 return bootstrap(MethodHandles.publicLookup(), opDesc, MethodType.methodType(rtype, ptypes), flags).dynamicInvoker(); 378 } 379 380 /** 381 * Returns a dynamic invoker for a specified dynamic operation using the public lookup. Similar to 382 * {@link #createDynamicInvoker(String, Class, Class...)} but with return and parameter types composed into a 383 * method type in the signature. See the discussion of that method for details. 384 * @param opDesc Dynalink dynamic operation descriptor. 385 * @param type the method type for the operation 386 * @return MethodHandle for invoking the operation. 387 */ 388 public static MethodHandle createDynamicInvoker(final String opDesc, final MethodType type) { 389 return bootstrap(MethodHandles.publicLookup(), opDesc, type, 0).dynamicInvoker(); 390 } 391 392 /** 393 * Binds any object Nashorn can use as a [[Callable]] to a receiver and optionally arguments. 394 * @param callable the callable to bind 395 * @param boundThis the bound "this" value. 396 * @param boundArgs the bound arguments. Can be either null or empty array to signify no arguments are bound. 397 * @return a bound callable. 398 * @throws ECMAException with {@code TypeError} if the object is not a callable. 399 */ 400 public static Object bindCallable(final Object callable, final Object boundThis, final Object[] boundArgs) { 401 if (callable instanceof ScriptFunctionImpl) { 402 return ((ScriptFunctionImpl)callable).makeBoundFunction(boundThis, boundArgs); 403 } else if (callable instanceof BoundCallable) { 404 return ((BoundCallable)callable).bind(boundArgs); 405 } else if (isCallable(callable)) { 406 return new BoundCallable(callable, boundThis, boundArgs); 407 } 408 throw notFunction(callable); 409 } 410 411 /** 412 * Creates a super-adapter for an adapter, that is, an adapter to the adapter that allows invocation of superclass 413 * methods on it. 414 * @param adapter the original adapter 415 * @return a new adapter that can be used to invoke super methods on the original adapter. 416 */ 417 public static Object createSuperAdapter(final Object adapter) { 418 return new JavaSuperAdapter(adapter); 419 } 420 421 /** 422 * If the given class is a reflection-specific class (anything in {@code java.lang.reflect} and 423 * {@code java.lang.invoke} package, as well a {@link Class} and any subclass of {@link ClassLoader}) and there is 424 * a security manager in the system, then it checks the {@code nashorn.JavaReflection} {@code RuntimePermission}. 425 * @param clazz the class being tested 426 * @param isStatic is access checked for static members (or instance members) 427 */ 428 public static void checkReflectionAccess(final Class<?> clazz, final boolean isStatic) { 429 ReflectionCheckLinker.checkReflectionAccess(clazz, isStatic); 430 } 431 432 /** 433 * Returns the Nashorn's internally used dynamic linker's services object. Note that in code that is processing a 434 * linking request, you will normally use the {@code LinkerServices} object passed by whatever top-level linker 435 * invoked the linking (if the call site is in Nashorn-generated code, you'll get this object anyway). You should 436 * only resort to retrieving a linker services object using this method when you need some linker services (e.g. 437 * type converter method handles) outside of a code path that is linking a call site. 438 * @return Nashorn's internal dynamic linker's services object. 439 */ 440 public static LinkerServices getLinkerServices() { 441 return dynamicLinker.getLinkerServices(); 442 } 443 444 /** 445 * Takes a guarded invocation, and ensures its method and guard conform to the type of the call descriptor, using 446 * all type conversions allowed by the linker's services. This method is used by Nashorn's linkers as a last step 447 * before returning guarded invocations. Most of the code used to produce the guarded invocations does not make an 448 * effort to coordinate types of the methods, and so a final type adjustment before a guarded invocation is returned 449 * to the aggregating linker is the responsibility of the linkers themselves. 450 * @param inv the guarded invocation that needs to be type-converted. Can be null. 451 * @param linkerServices the linker services object providing the type conversions. 452 * @param desc the call site descriptor to whose method type the invocation needs to conform. 453 * @return the type-converted guarded invocation. If input is null, null is returned. If the input invocation 454 * already conforms to the requested type, it is returned unchanged. 455 */ 456 static GuardedInvocation asTypeSafeReturn(final GuardedInvocation inv, final LinkerServices linkerServices, final CallSiteDescriptor desc) { 457 return inv == null ? null : inv.asTypeSafeReturn(linkerServices, desc.getMethodType()); 458 } 459 460 /** 461 * Adapts the return type of the method handle with {@code explicitCastArguments} when it is an unboxing 462 * conversion. This will ensure that nulls are unwrapped to false or 0. 463 * @param target the target method handle 464 * @param newType the desired new type. Note that this method does not adapt the method handle completely to the 465 * new type, it only adapts the return type; this is allowed as per 466 * {@link DynamicLinkerFactory#setAutoConversionStrategy(MethodTypeConversionStrategy)}, which is what this method 467 * is used for. 468 * @return the method handle with adapted return type, if it required an unboxing conversion. 469 */ 470 private static MethodHandle unboxReturnType(final MethodHandle target, final MethodType newType) { 471 final MethodType targetType = target.type(); 472 final Class<?> oldReturnType = targetType.returnType(); 473 final Class<?> newReturnType = newType.returnType(); 474 if (TypeUtilities.isWrapperType(oldReturnType)) { 475 if (newReturnType.isPrimitive()) { 476 // The contract of setAutoConversionStrategy is such that the difference between newType and targetType 477 // can only be JLS method invocation conversions. 478 assert TypeUtilities.isMethodInvocationConvertible(oldReturnType, newReturnType); 479 return MethodHandles.explicitCastArguments(target, targetType.changeReturnType(newReturnType)); 480 } 481 } else if (oldReturnType == void.class && newReturnType == Object.class) { 482 return MethodHandles.filterReturnValue(target, VOID_TO_OBJECT); 483 } 484 return target; 485 } 486} 487