--- a/graal/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/typesystem/TypeSystemParser.java	Tue Jan 07 12:22:47 2014 +0100
+++ b/graal/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/typesystem/TypeSystemParser.java	Tue Jan 07 18:52:32 2014 +0100
@@ -35,7 +35,7 @@
 import com.oracle.truffle.dsl.processor.*;
 import com.oracle.truffle.dsl.processor.template.*;
 
-public class TypeSystemParser extends TemplateParser<TypeSystemData> {
+public class TypeSystemParser extends AbstractParser<TypeSystemData> {
 
     public static final List<Class<? extends Annotation>> ANNOTATIONS = Arrays.asList(TypeSystem.class, ExpectError.class);
 
@@ -115,6 +115,28 @@
         return typeSystem;
     }
 
+    protected void verifyExclusiveMethodAnnotation(Template template, Class<?>... annotationTypes) {
+        List<ExecutableElement> methods = ElementFilter.methodsIn(template.getTemplateType().getEnclosedElements());
+        for (ExecutableElement method : methods) {
+            List<AnnotationMirror> foundAnnotations = new ArrayList<>();
+            for (int i = 0; i < annotationTypes.length; i++) {
+                Class<?> annotationType = annotationTypes[i];
+                AnnotationMirror mirror = Utils.findAnnotationMirror(context.getEnvironment(), method, annotationType);
+                if (mirror != null) {
+                    foundAnnotations.add(mirror);
+                }
+            }
+            if (foundAnnotations.size() > 1) {
+                List<String> annotationNames = new ArrayList<>();
+                for (AnnotationMirror mirror : foundAnnotations) {
+                    annotationNames.add("@" + Utils.getSimpleName(mirror.getAnnotationType()));
+                }
+
+                template.addError("Non exclusive usage of annotations %s.", annotationNames);
+            }
+        }
+    }
+
     private static void verifyGenericTypeChecksAndCasts(TypeSystemData typeSystem) {
         for (TypeData type : typeSystem.getTypes()) {
             if (!type.getTypeChecks().isEmpty()) {