Explicitly tell 'getNameToInstances' mods to load

Calculating which modules to load based on the InteractiveContext means
maintaining a potentially very large GblRdrEnv.

In Haddock's case, it is much cheaper (from a memory perspective) to
just keep track of which modules interfaces we want loaded then hand
these off explicitly to 'getNameToInstancesIndex'.

Bumps haddock submodule.

Reviewers: alexbiehl, bgamari

Reviewed By: alexbiehl

Subscribers: rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D5003

1 files changed, 13 insertions, 5 deletions

diff --git a/compiler/main/GHC.hs b/compiler/main/GHC.hs
index 0e20e21fdb..29921de8cd 100644
--- a/compiler/main/GHC.hs
+++ b/compiler/main/GHC.hs
@@ -300,7 +300,8 @@ import HscMain
 import GhcMake
 import DriverPipeline   ( compileOne' )
 import GhcMonad
-import TcRnMonad        ( finalSafeMode, fixSafeInstances )
+import TcRnMonad        ( finalSafeMode, fixSafeInstances, initIfaceTcRn )
+import LoadIface        ( loadSysInterface )
 import TcRnTypes
 import Packages
 import NameSet
@@ -1247,13 +1248,20 @@ getGRE = withSession $ \hsc_env-> return $ ic_rn_gbl_env (hsc_IC hsc_env)
 -- by 'Name'. Each name's lists will contain every instance in which that name
 -- is mentioned in the instance head.
 getNameToInstancesIndex :: GhcMonad m
-  => [Module]  -- ^ visible modules. An orphan instance will be returned if and
-               -- only it is visible from at least one module in the list.
+  => [Module]        -- ^ visible modules. An orphan instance will be returned
+                     -- if it is visible from at least one module in the list.
+  -> Maybe [Module]  -- ^ modules to load. If this is not specified, we load
+                     -- modules for everything that is in scope unqualified.
   -> m (Messages, Maybe (NameEnv ([ClsInst], [FamInst])))
-getNameToInstancesIndex visible_mods = do
+getNameToInstancesIndex visible_mods mods_to_load = do
   hsc_env <- getSession
   liftIO $ runTcInteractive hsc_env $
-    do { loadUnqualIfaces hsc_env (hsc_IC hsc_env)
+    do { case mods_to_load of
+           Nothing -> loadUnqualIfaces hsc_env (hsc_IC hsc_env)
+           Just mods ->
+             let doc = text "Need interface for reporting instances in scope"
+             in initIfaceTcRn $ mapM_ (loadSysInterface doc) mods
+
        ; InstEnvs {ie_global, ie_local} <- tcGetInstEnvs
        ; let visible_mods' = mkModuleSet visible_mods
        ; (pkg_fie, home_fie) <- tcGetFamInstEnvs