+Note [Annotations]
+~~~~~~~~~~~~~~~~~~
+A Core-to-Core pass that wants to make use of annotations calls
+getAnnotations or getFirstAnnotations at the beginning to obtain a UniqFM with
+annotations of a specific type. This produces all annotations from interface
+files read so far. However, annotations from interface files read during the
+pass will not be visible until getAnnotations is called again. This is similar
+to how rules work and probably isn't too bad.
+
+The current implementation could be optimised a bit: when looking up
+annotations for a thing from the HomePackageTable, we could search directly in
+the module where the thing is defined rather than building one UniqFM which
+contains all annotations we know of. This would work because annotations can
+only be given to things defined in the same module. However, since we would
+only want to deserialise every annotation once, we would have to build a cache
+for every module in the HTP. In the end, it's probably not worth it as long as
+we aren't using annotations heavily.