Fix data race in crosslink.

This was introduced by the previous fix for delimited inheritance, and was never released.  This fix removes all getType() calls from crosslink, where it's not safe to inspect the message type, which is still a placeholder, until after crosslinking.  Using the inferred type is not necessary since we treat messages and groups the same during crosslink.

PiperOrigin-RevId: 643394981

Author: mkruskal-google

java/core/src/main/java/com/google/protobuf/Descriptors.java

@@ -1901,7 +1901,9 @@ private void crossLink() throws DescriptorValidationException {
           }
         }
 
-        if (getJavaType() == JavaType.MESSAGE) {
+        // Use raw type since inferred type considers messageType which may not be fully cross
+        // linked yet.
+        if (type.getJavaType() == JavaType.MESSAGE) {
           if (!(typeDescriptor instanceof Descriptor)) {
             throw new DescriptorValidationException(
                 this, '\"' + proto.getTypeName() + "\" is not a message type.");
@@ -1911,7 +1913,7 @@ private void crossLink() throws DescriptorValidationException {
           if (proto.hasDefaultValue()) {
             throw new DescriptorValidationException(this, "Messages can't have default values.");
           }
-        } else if (getJavaType() == JavaType.ENUM) {
+        } else if (type.getJavaType() == JavaType.ENUM) {
           if (!(typeDescriptor instanceof EnumDescriptor)) {
             throw new DescriptorValidationException(
                 this, '\"' + proto.getTypeName() + "\" is not an enum type.");
@@ -1921,7 +1923,7 @@ private void crossLink() throws DescriptorValidationException {
           throw new DescriptorValidationException(this, "Field with primitive type has type_name.");
         }
       } else {
-        if (getJavaType() == JavaType.MESSAGE || getJavaType() == JavaType.ENUM) {
+        if (type.getJavaType() == JavaType.MESSAGE || type.getJavaType() == JavaType.ENUM) {
           throw new DescriptorValidationException(
               this, "Field with message or enum type missing type_name.");
         }
@@ -1942,7 +1944,7 @@ private void crossLink() throws DescriptorValidationException {
         }
 
         try {
-          switch (getType()) {
+          switch (type) {
             case INT32:
             case SINT32:
             case SFIXED32:
@@ -2017,7 +2019,7 @@ private void crossLink() throws DescriptorValidationException {
         if (isRepeated()) {
           defaultValue = Collections.emptyList();
         } else {
-          switch (getJavaType()) {
+          switch (type.getJavaType()) {
             case ENUM:
               // We guarantee elsewhere that an enum type always has at least
               // one possible value.
@@ -2027,7 +2029,7 @@ private void crossLink() throws DescriptorValidationException {
               defaultValue = null;
               break;
             default:
-              defaultValue = getJavaType().defaultDefault;
+              defaultValue = type.getJavaType().defaultDefault;
               break;
           }
         }