Actually force usages

In 00f4e61 we attempted to share the filepaths in GHC's usage field.
Unfortunately the `mi_usages` field is lazy and so these turned out to not actually be shared because
the thunk responsible for sharing was never evaluated.

Add the right strictness annotations to ensure these are actually shared

Author: wz1000

ghcide/src/Development/IDE/Core/Compile.hs

@@ -36,6 +36,7 @@ module Development.IDE.Core.Compile
   , TypecheckHelpers(..)
   , sourceTypecheck
   , sourceParser
+  , shareUsages
   ) where
 
 import           Control.Monad.IO.Class
@@ -469,7 +470,7 @@ filterUsages = id
 
 -- | Mitigation for https://gitlab.haskell.org/ghc/ghc/-/issues/22744
 shareUsages :: ModIface -> ModIface
-shareUsages iface = iface {mi_usages = usages}
+shareUsages iface = rnf usages `seq` iface {mi_usages = usages}
   where usages = map go (mi_usages iface)
         go usg@UsageFile{} = usg {usg_file_path = fp}
           where !fp = shareFilePath (usg_file_path usg)

ghcide/src/Development/IDE/GHC/Orphans.hs

@@ -242,3 +242,7 @@ instance NFData (HsExpr (GhcPass 'Renamed)) where
 
 instance NFData Extension where
   rnf = rwhnf
+
+instance NFData Usage where
+  rnf (UsageFile a b c) = rnf a `seq` rnf b `seq` rnf c
+  rnf x = ()