-- There will be a node for each source module, plus a node for each hi-boot
-- module.
--
--- The graph is not necessarily stored in topologically-sorted order.
+-- The graph is not necessarily stored in topologically-sorted order. Use
+-- 'GHC.topSortModuleGraph' and 'Digraph.flattenSCC' to achieve this.
type ModuleGraph = [ModSummary]
emptyMG :: ModuleGraph