support for TYPE_USE @nullable

value/src/main/java/com/google/auto/value/processor/AutoValueProcessor.java

@@ -216,6 +216,10 @@ private ImmutableList<String> buildAnnotations(TypeSimplifier typeSimplifier) {
         builder.add(annotationOutput.sourceFormForAnnotation(annotationMirror));
       }
 
+      for (AnnotationMirror annotationMirror : Java8Support.getAnnotationMirrors(method.getReturnType())) {
+        AnnotationOutput annotationOutput = new AnnotationOutput(typeSimplifier);
+        builder.add(annotationOutput.sourceFormForAnnotation(annotationMirror));
+      }
       return builder.build();
     }
 
@@ -541,6 +545,9 @@ private Set<TypeMirror> allMethodAnnotationTypes(Iterable<ExecutableElement> met
       for (AnnotationMirror annotationMirror : method.getAnnotationMirrors()) {
         annotationTypes.add(annotationMirror.getAnnotationType());
       }
+      for (AnnotationMirror annotationMirror : Java8Support.getAnnotationMirrors(method.getReturnType())) {
+        annotationTypes.add(annotationMirror.getAnnotationType());
+      }
     }
     return annotationTypes;
   }

value/src/main/java/com/google/auto/value/processor/Java8Support.java

@@ -0,0 +1,51 @@
+package com.google.auto.value.processor;
+
+import java.lang.reflect.Method;
+import java.util.Collections;
+import java.util.List;
+
+import javax.lang.model.element.AnnotationMirror;
+import javax.lang.model.type.TypeMirror;
+
+/**
+ * this class provides access to java 8 type annotations via reflection (to
+ * still allow running on older java versions).
+ * 
+ * @author Till Brychcy
+ */
+public class Java8Support {
+    private static Method determineAnnotationsMirrorsMethod() {
+        try {
+            return Class.forName("javax.lang.model.AnnotatedConstruct")
+                    .getMethod("getAnnotationMirrors");
+        } catch (Exception e) {
+            // method and type only exist on java 8 and later
+            return null;
+        }
+    }
+
+    static Method getAnnotationsMirrorsMethod = determineAnnotationsMirrorsMethod();
+
+    /**
+     * provides access to
+     * {@link javax.lang.model.AnnotatedConstruct#getAnnotationMirrors()} via
+     * reflection
+     * 
+     * @param typeMirror
+     * @return if possible, the result of typeMirror.getAnnotationMirrors(),
+     *         otherwise an empty list.
+     */
+    @SuppressWarnings("unchecked")
+    static List<? extends AnnotationMirror> getAnnotationMirrors(TypeMirror typeMirror) {
+        try {
+            if (getAnnotationsMirrorsMethod != null) {
+                return (List<? extends AnnotationMirror>) getAnnotationsMirrorsMethod
+                        .invoke(typeMirror);
+            } else {
+                return Collections.emptyList();
+            }
+        } catch (Exception e) {
+            throw new RuntimeException("exception during invocation of getAnnotationMirrors", e);
+        }
+    }
+}