Bug 434378

Description Jonathan Fuerth 2014-05-07 18:49:55 EDT

org.eclipse.jdt.apt.core version 3.3.500.v20120516-0617

Under JDT APT, the return value of Types.getNoType(TypeKind.VOID) does not work properly with Types.isAssignable(). isAssignable() should say the return type of a void method is assignable to the TypeMirror returned by Types.getNoType(TypeKind.VOID), but it does not. (Javac does)

Here's a recipe for reproducing the issue. Given the following annotation:

------
package ca.fuerth.junk.ap;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * An example annotation that comes with a processor that ensures the target method returns void.
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface VoidMethod {

}
------


And the following annotation processor:

------
package ca.fuerth.junk.ap;

import java.util.Set;

import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.Element;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.TypeElement;
import javax.lang.model.type.TypeKind;
import javax.lang.model.type.TypeMirror;
import javax.lang.model.util.Types;
import javax.tools.Diagnostic.Kind;

/**
 * An example annotation processor that ensures methods annotated with {@code @VoidMethod} return void.
 */
@SupportedAnnotationTypes("ca.fuerth.junk.ap.VoidMethod")
@SupportedSourceVersion(SourceVersion.RELEASE_6)
public class VoidMethodAnnotationProcessor extends AbstractProcessor {

    @Override
    public boolean process( Set<? extends TypeElement> annotations, RoundEnvironment roundEnv ) {
        final Types typeUtils = processingEnv.getTypeUtils();
        for (TypeElement annotation : annotations) {
            for (Element method : roundEnv.getElementsAnnotatedWith( annotation )) {
                TypeMirror voidType = typeUtils.getNoType( TypeKind.VOID );
                if (!typeUtils.isAssignable( ((ExecutableElement) method).getReturnType(), voidType )) {
                    processingEnv.getMessager().printMessage( Kind.ERROR, "This method has to return void", method );
                } else {
                    processingEnv.getMessager().printMessage( Kind.WARNING, "Looks good!", method );
                }
            }
        }
        return true;
    }
}
------


Then the following class (in a separate project in a separate workspace, as required by JDT APT):

------
package ca.fuerth.misc;

import ca.fuerth.junk.ap.VoidMethod;


public class HasVoidMethodAnnotation {

    @VoidMethod
    public void thisIsAVoidMethod() {
        return;
    }
}
------

gets an error marker "This method has to return void" on the annotated method.

Compiling the same file under javac results in the warning message "Looks good!"