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
@@ -468,6 +469,8 @@ filterUsages = id
 #endif
 
 -- | Mitigation for https://gitlab.haskell.org/ghc/ghc/-/issues/22744
+-- Important to do this immediately after reading the unit before
+-- anything else has a chance to read `mi_usages`
 shareUsages :: ModIface -> ModIface
 shareUsages iface = iface {mi_usages = usages}
   where usages = map go (mi_usages iface)
@@ -1479,11 +1482,23 @@ loadInterface session ms linkableNeeded RecompilationInfo{..} = do
             | source_version <= dest_version -> SourceUnmodified
             | otherwise -> SourceModified
 
+    old_iface <- case mb_old_iface of
+      Just iface -> pure (Just iface)
+      Nothing -> do
+        let ncu = hsc_NC sessionWithMsDynFlags
+            dflags = hsc_dflags sessionWithMsDynFlags
+        read_result <- readIface read_dflags ncu mod iface_file
+        case read_result of
+          Failed _err -> return Nothing
+          -- important to call `shareUsages` here before checkOldIface
+          -- consults `mi_usages`
+          Just iface -> return $ Just (shareUsages iface)
+
     -- If mb_old_iface is nothing then checkOldIface will load it for us
     -- given that the source is unmodified
     (recomp_iface_reqd, mb_checked_iface)
 #if MIN_VERSION_ghc(9,3,0)
-      <- liftIO $ checkOldIface sessionWithMsDynFlags ms mb_old_iface >>= \case
+      <- liftIO $ checkOldIface sessionWithMsDynFlags ms old_iface >>= \case
         UpToDateItem x -> pure (UpToDate, Just x)
         OutOfDateItem reason x -> pure (NeedsRecompile reason, x)
 #else
@@ -1498,7 +1513,6 @@ loadInterface session ms linkableNeeded RecompilationInfo{..} = do
 
     case (mb_checked_iface, recomp_iface_reqd) of
       (Just iface', UpToDate) -> do
-             let iface = shareUsages iface'
              details <- liftIO $ mkDetailsFromIface sessionWithMsDynFlags iface
              -- parse the runtime dependencies from the annotations
              let runtime_deps