/**
* Adapts the return type of the method handle with {@code explicitCastArguments} when it is an
* unboxing conversion. This will ensure that nulls are unwrapped to false or 0.
*
* @param target the target method handle
* @param newType the desired new type. Note that this method does not adapt the method handle
* completely to the new type, it only adapts the return type; this is allowed as per {@link
* DynamicLinkerFactory#setAutoConversionStrategy(MethodTypeConversionStrategy)}, which is
* what this method is used for.
* @return the method handle with adapted return type, if it required an unboxing conversion.
*/
private static MethodHandle unboxReturnType(final MethodHandle target, final MethodType newType) {
final MethodType targetType = target.type();
final Class<?> oldReturnType = targetType.returnType();
final Class<?> newReturnType = newType.returnType();
if (TypeUtilities.isWrapperType(oldReturnType)) {
if (newReturnType.isPrimitive()) {
// The contract of setAutoConversionStrategy is such that the difference between newType and
// targetType
// can only be JLS method invocation conversions.
assert TypeUtilities.isMethodInvocationConvertible(oldReturnType, newReturnType);
return MethodHandles.explicitCastArguments(
target, targetType.changeReturnType(newReturnType));
}
} else if (oldReturnType == void.class && newReturnType == Object.class) {
return MethodHandles.filterReturnValue(target, VOID_TO_OBJECT);
}
return target;
}
private static boolean canWiden(final Class<?> type) {
return TypeUtilities.isWrapperType(type) && type != Boolean.class && type != Character.class;
}