Make ValueType#getDisplayName abstract since ValueType#hasDisplayName returning true requires that any subclass must override getDisplayName.
@@ -54,6 +54,10 @@ abstract class ValueType extends JSType {
return this;
}
+ // Subclasses must override and return non-null.
+ @Override
+ public abstract String getDisplayName();
+
@Override
public boolean hasDisplayName() {
return true;
