Haddock support for bundled pattern synonyms (#627)

* Haddock support for bundled pattern synonyms

* Add fixities to bundled pattern synonyms

* Add bundled pattern synonyms to the synopsis

* Store bundled pattern fixities in expItemFixities

* Add test for bundled pattern synonyms

* Stop threading fixities

* Include bundled pattern synonyms for re-exported data types

Sadly, fixity information isn't found for re-exported data types

* Support for pattern synonyms

* Modify tests after #631

* Test some reexport variations

* Also lookup bundled pattern synonyms from `InstalledInterface`s

* Check isExported for bundled pattern synonyms

* Pattern synonym is exported check

* Always look for pattern synonyms in the current module

Another overlooked cornercase

* Account for types named twice in export lists

Also introduce a fast function for nubbing on a `Name` and use it
throughout the code base.

* correct fixities for reexported pattern synonyms

* Fuse concatMap and map

* Remove obsolete import

* Add pattern synonyms to visible exports

* Fix test

* Remove corner case

1 files changed, 7 insertions, 4 deletions

diff --git a/haddock-api/src/Haddock/Interface/AttachInstances.hs b/haddock-api/src/Haddock/Interface/AttachInstances.hs
index d5d74819..7a3182b8 100644
--- a/haddock-api/src/Haddock/Interface/AttachInstances.hs
+++ b/haddock-api/src/Haddock/Interface/AttachInstances.hs
@@ -21,7 +21,6 @@ import Haddock.GhcUtils
 import Control.Arrow hiding ((<+>))
 import Data.List
 import Data.Ord (comparing)
-import Data.Function (on)
 import Data.Maybe ( maybeToList, mapMaybe )
 import qualified Data.Map as Map
 import qualified Data.Set as Set
@@ -109,13 +108,17 @@ attachToExportItem expInfo iface ifaceMap instIfaceMap export =
       return $ e { expItemInstances = insts }
     e -> return e
   where
-    attachFixities e@ExportDecl{ expItemDecl = L _ d } = e { expItemFixities =
-      nubBy ((==) `on` fst) $ expItemFixities e ++
+    attachFixities e@ExportDecl{ expItemDecl = L _ d
+                               , expItemPats = patsyns
+                               } = e { expItemFixities =
+      nubByName fst $ expItemFixities e ++
       [ (n',f) | n <- getMainDeclBinder d
               , Just subs <- [instLookup instSubMap n iface ifaceMap instIfaceMap]
-              , n' <- n : subs
+              , n' <- n : (subs ++ patsyn_names)
               , Just f <- [instLookup instFixMap n' iface ifaceMap instIfaceMap]
       ] }
+      where
+        patsyn_names = concatMap (getMainDeclBinder . fst) patsyns
 
     attachFixities e = e
     -- spanName: attach the location to the name that is the same file as the instance location