Hi, As you can see in http://ghc.haskell.org/trac/ghc/ticket/5144#comment:18, my implementation of pattern synonyms is now feature complete for the first two sections of http://ghc.haskell.org/trac/ghc/wiki/PatternSynonyms, namely, simple pattern synonyms and pattern-only synonyms. Bidirectional pattern synonyms using 'where' will also be easy to add and will be part of my initial submission. The current version of my code is at https://github.com/gergoerdi/ghc/compare/pattern-synonyms However, the one part I am struggling with is implementing exporting of pattern synonyms. The pipeline is pretty clear to get the pattern synonym definitions to the ModGuts, but I get lost there. Since they are a completely compile-time thing, there's nothing to put in the CgGuts (well, I guess the wrapper (i.e. the patsyn-in-an-expression-context) should be put there). However, when I look at existing stuff in ModIface/ModDetails, I don't really see a pattern for storing actual definitions there. Could someone help me with this part please? Would it make sense to put something like https://raw.github.com/gergoerdi/ghc/pattern-synonyms/compiler/basicTypes/Pa... in the interface? Or put the "psPatDef" and the "fmap snd psWrapper" parts in the CgGuts and the rest in the interface? Thanks, Gergo -- .--= ULLA! =-----------------. \ http://gergo.erdi.hu \ `---= gergo@erdi.hu =-------'