8057656: Improve MethodType.isCastableTo() & MethodType.isConvertibleTo() checks
Reviewed-by: vlivanov, psandoz
diff --git a/jdk/src/java.base/share/classes/java/lang/invoke/MethodHandles.java b/jdk/src/java.base/share/classes/java/lang/invoke/MethodHandles.java
index d12b7c2..47bff79 100644
--- a/jdk/src/java.base/share/classes/java/lang/invoke/MethodHandles.java
+++ b/jdk/src/java.base/share/classes/java/lang/invoke/MethodHandles.java
@@ -2024,8 +2024,11 @@
*/
public static
MethodHandle explicitCastArguments(MethodHandle target, MethodType newType) {
- if (!target.type().isCastableTo(newType)) {
- throw new WrongMethodTypeException("cannot explicitly cast "+target+" to "+newType);
+ MethodType oldType = target.type();
+ // use the asTypeCache when possible:
+ if (oldType == newType) return target;
+ if (oldType.explicitCastEquivalentToAsType(newType)) {
+ return target.asType(newType);
}
return MethodHandleImpl.makePairwiseConvert(target, newType, false);
}
diff --git a/jdk/src/java.base/share/classes/java/lang/invoke/MethodType.java b/jdk/src/java.base/share/classes/java/lang/invoke/MethodType.java
index bf592fe..2762227 100644
--- a/jdk/src/java.base/share/classes/java/lang/invoke/MethodType.java
+++ b/jdk/src/java.base/share/classes/java/lang/invoke/MethodType.java
@@ -825,29 +825,111 @@
return true;
}
/*non-public*/
- boolean isCastableTo(MethodType newType) {
- int argc = parameterCount();
- if (argc != newType.parameterCount())
- return false;
- return true;
- }
- /*non-public*/
boolean isConvertibleTo(MethodType newType) {
+ MethodTypeForm oldForm = this.form();
+ MethodTypeForm newForm = newType.form();
+ if (oldForm == newForm)
+ // same parameter count, same primitive/object mix
+ return true;
if (!canConvert(returnType(), newType.returnType()))
return false;
- int argc = parameterCount();
- if (argc != newType.parameterCount())
+ Class<?>[] srcTypes = newType.ptypes;
+ Class<?>[] dstTypes = ptypes;
+ if (srcTypes == dstTypes)
+ return true;
+ int argc;
+ if ((argc = srcTypes.length) != dstTypes.length)
return false;
- for (int i = 0; i < argc; i++) {
- if (!canConvert(newType.parameterType(i), parameterType(i)))
+ if (argc <= 1) {
+ if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0]))
return false;
+ return true;
+ }
+ if ((oldForm.primitiveParameterCount() == 0 && oldForm.erasedType == this) ||
+ (newForm.primitiveParameterCount() == 0 && newForm.erasedType == newType)) {
+ // Somewhat complicated test to avoid a loop of 2 or more trips.
+ // If either type has only Object parameters, we know we can convert.
+ assert(canConvertParameters(srcTypes, dstTypes));
+ return true;
+ }
+ return canConvertParameters(srcTypes, dstTypes);
+ }
+
+ /** Returns true if MHs.explicitCastArguments produces the same result as MH.asType.
+ * If the type conversion is impossible for either, the result should be false.
+ */
+ /*non-public*/
+ boolean explicitCastEquivalentToAsType(MethodType newType) {
+ if (this == newType) return true;
+ if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) {
+ return false;
+ }
+ Class<?>[] srcTypes = newType.ptypes;
+ Class<?>[] dstTypes = ptypes;
+ if (dstTypes == srcTypes) {
+ return true;
+ }
+ if (dstTypes.length != srcTypes.length) {
+ return false;
+ }
+ for (int i = 0; i < dstTypes.length; i++) {
+ if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) {
+ return false;
+ }
}
return true;
}
+
+ /** Reports true if the src can be converted to the dst, by both asType and MHs.eCE,
+ * and with the same effect.
+ * MHs.eCA has the following "upgrades" to MH.asType:
+ * 1. interfaces are unchecked (that is, treated as if aliased to Object)
+ * Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics
+ * 2. the full matrix of primitive-to-primitive conversions is supported
+ * Narrowing like {@code long->byte} and basic-typing like {@code boolean->int}
+ * are not supported by asType, but anything supported by asType is equivalent
+ * with MHs.eCE.
+ * 3a. unboxing conversions can be followed by the full matrix of primitive conversions
+ * 3b. unboxing of null is permitted (creates a zero primitive value)
+ * Most unboxing conversions, like {@code Object->int}, has potentially
+ * different behaviors for asType vs. MHs.eCE, because the dynamic value
+ * might be a wrapper of a type that requires narrowing, like {@code (Object)1L->byte}.
+ * The equivalence is only certain if the static src type is a wrapper,
+ * and the conversion will be a widening one.
+ * Other than interfaces, reference-to-reference conversions are the same.
+ * Boxing primitives to references is the same for both operators.
+ */
+ private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) {
+ if (src == dst || dst == Object.class || dst == void.class) return true;
+ if (src.isPrimitive()) {
+ // Could be a prim/prim conversion, where casting is a strict superset.
+ // Or a boxing conversion, which is always to an exact wrapper class.
+ return canConvert(src, dst);
+ } else if (dst.isPrimitive()) {
+ Wrapper dw = Wrapper.forPrimitiveType(dst);
+ // Watch out: If src is Number or Object, we could get dynamic narrowing conversion.
+ // The conversion is known to be widening only if the wrapper type is statically visible.
+ return (Wrapper.isWrapperType(src) &&
+ dw.isConvertibleFrom(Wrapper.forWrapperType(src)));
+ } else {
+ // R->R always works, but we have to avoid a check-cast to an interface.
+ return !dst.isInterface() || dst.isAssignableFrom(src);
+ }
+ }
+
+ private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) {
+ for (int i = 0; i < srcTypes.length; i++) {
+ if (!canConvert(srcTypes[i], dstTypes[i])) {
+ return false;
+ }
+ }
+ return true;
+ }
+
/*non-public*/
static boolean canConvert(Class<?> src, Class<?> dst) {
// short-circuit a few cases:
- if (src == dst || dst == Object.class) return true;
+ if (src == dst || src == Object.class || dst == Object.class) return true;
// the remainder of this logic is documented in MethodHandle.asType
if (src.isPrimitive()) {
// can force void to an explicit null, a la reflect.Method.invoke