com.oracle.truffle.api.library

Annotation Type GenerateLibrary.Abstract

@Retention(value=CLASS)
 @Target(value=METHOD)
public static @interface GenerateLibrary.Abstract

Makes a library message abstract, but allows to keep a default implementation. By default, abstract messages throw an AbstractMethodError if they are not exported for a given receiver type. To customize this behavior the library message can specify a method body and annotate it with GenerateLibrary.Abstract to keep requiring an implementation from exports.

For example:

 @GenerateLibrary
 public abstract class ArrayLibrary extends Library {

     @Abstract(ifExported = "read")
     public boolean isArray(Object receiver) {
         return false;
     }

     @Abstract(ifExported = "isArray")
     public int read(Object receiver, int index) {
         throw new UnsupportedOperationException();
     }
 }
 

In this example a receiver that does not export the ArrayLibrary will return false for isArray and throw an UnsupportedOperationException for read calls. A message may be made conditionally abstract by specifying the GenerateLibrary.Abstract.ifExported() attribute.

Since:

19.0

See Also:

GenerateLibrary.Abstract.ifExported()

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
String[]	ifExported Specifies a message to be abstract only if another message is implemented.

Element Detail

ifExported

public abstract String[] ifExported

Specifies a message to be abstract only if another message is implemented. Multiple other messages can be specified.

For example:

 @GenerateLibrary
 public abstract class ArrayLibrary extends Library {

     @Abstract(ifExported = "read")
     public boolean isArray(Object receiver) {
         return false;
     }

     @Abstract(ifExported = "isArray")
     public int read(Object receiver, int index) {
         throw new UnsupportedOperationException();
     }
 }
 

In this example the isArray message only needs to be exported if the read message is exported and vice-versa.

Since:

19.0

Default:

{}