8235274: Enhance typing of methods

Reviewed-by: jrose, psandoz, skoivu

Author: Roger Riggs

src/java.base/share/classes/java/lang/invoke/MethodType.java

@@ -116,7 +116,8 @@ class MethodType
 
     // The remaining fields are caches of various sorts:
     private @Stable MethodTypeForm form; // erased form, plus cached data about primitives
-    private @Stable MethodType wrapAlt;  // alternative wrapped/unwrapped version
+    private @Stable Object wrapAlt;  // alternative wrapped/unwrapped version and
+                                     // private communication for readObject and readResolve
     private @Stable Invokers invokers;   // cache of handy higher-order adapters
     private @Stable String methodDescriptor;  // cache for toMethodDescriptorString
 
@@ -711,7 +712,7 @@ public MethodType unwrap() {
 
     private static MethodType wrapWithPrims(MethodType pt) {
         assert(pt.hasPrimitives());
-        MethodType wt = pt.wrapAlt;
+        MethodType wt = (MethodType)pt.wrapAlt;
         if (wt == null) {
             // fill in lazily
             wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP);
@@ -723,7 +724,7 @@ private static MethodType wrapWithPrims(MethodType pt) {
 
     private static MethodType unwrapWithNoPrims(MethodType wt) {
         assert(!wt.hasPrimitives());
-        MethodType uwt = wt.wrapAlt;
+        MethodType uwt = (MethodType)wt.wrapAlt;
         if (uwt == null) {
             // fill in lazily
             uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP);
@@ -1248,27 +1249,18 @@ private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOExceptio
      */
     @java.io.Serial
     private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
-        // Assign temporary defaults in case this object escapes
-        MethodType_init(void.class, NO_PTYPES);
+        // Assign defaults in case this object escapes
+        UNSAFE.putReference(this, OffsetHolder.rtypeOffset, void.class);
+        UNSAFE.putReference(this, OffsetHolder.ptypesOffset, NO_PTYPES);
 
         s.defaultReadObject();  // requires serialPersistentFields to be an empty array
 
         Class<?>   returnType     = (Class<?>)   s.readObject();
         Class<?>[] parameterArray = (Class<?>[]) s.readObject();
-        parameterArray = parameterArray.clone();  // make sure it is unshared
 
-        // Assign deserialized values
-        MethodType_init(returnType, parameterArray);
-    }
-
-    // Initialization of state for deserialization only
-    private void MethodType_init(Class<?> rtype, Class<?>[] ptypes) {
-        // In order to communicate these values to readResolve, we must
-        // store them into the implementation-specific final fields.
-        checkRtype(rtype);
-        checkPtypes(ptypes);
-        UNSAFE.putReference(this, OffsetHolder.rtypeOffset, rtype);
-        UNSAFE.putReference(this, OffsetHolder.ptypesOffset, ptypes);
+        // Verify all operands, and make sure ptypes is unshared
+        // Cache the new MethodType for readResolve
+        wrapAlt = new MethodType[]{MethodType.methodType(returnType, parameterArray)};
     }
 
     // Support for resetting final fields while deserializing. Implement Holder
@@ -1291,12 +1283,10 @@ private Object readResolve() {
         // Do not use a trusted path for deserialization:
         //    return makeImpl(rtype, ptypes, true);
         // Verify all operands, and make sure ptypes is unshared:
-        try {
-            return methodType(rtype, ptypes);
-        } finally {
-            // Re-assign defaults in case this object escapes
-            MethodType_init(void.class, NO_PTYPES);
-        }
+        // Return a new validated MethodType for the rtype and ptypes passed from readObject.
+        MethodType mt = ((MethodType[])wrapAlt)[0];
+        wrapAlt = null;
+        return mt;
     }
 
     /**