Minor performance optimizations (#1432)

* Use a newtype

* Avoid O(n) operation in loop

HMS.size is O(n) and getPathId gets called in the rawDependencyInformation loop

Co-authored-by: Junyoung/Clare Jang <jjc9310@gmail.com>

Author: pepeiborra

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

@@ -250,7 +250,7 @@ type instance RuleResult GetModIfaceWithoutLinkable = HiFileResult
 type instance RuleResult GetFileContents = (FileVersion, Maybe Text)
 
 -- The Shake key type for getModificationTime queries
-data GetModificationTime = GetModificationTime_
+newtype GetModificationTime = GetModificationTime_
     { missingFileDiagnostics :: Bool
       -- ^ If false, missing file diagnostics are not reported
     }

ghcide/src/Development/IDE/Import/DependencyInformation.hs

@@ -76,25 +76,29 @@ type FilePathIdSet = IntSet
 data PathIdMap = PathIdMap
   { idToPathMap :: !(FilePathIdMap ArtifactsLocation)
   , pathToIdMap :: !(HashMap NormalizedFilePath FilePathId)
+  , nextFreshId :: !Int
   }
   deriving (Show, Generic)
 
 instance NFData PathIdMap
 
 emptyPathIdMap :: PathIdMap
-emptyPathIdMap = PathIdMap IntMap.empty HMS.empty
+emptyPathIdMap = PathIdMap IntMap.empty HMS.empty 0
 
 getPathId :: ArtifactsLocation -> PathIdMap -> (FilePathId, PathIdMap)
 getPathId path m@PathIdMap{..} =
     case HMS.lookup (artifactFilePath path) pathToIdMap of
         Nothing ->
-            let !newId = FilePathId $ HMS.size pathToIdMap
+            let !newId = FilePathId nextFreshId
             in (newId, insertPathId path newId m)
         Just id -> (id, m)
-
-insertPathId :: ArtifactsLocation -> FilePathId -> PathIdMap -> PathIdMap
-insertPathId path id PathIdMap{..} =
-    PathIdMap (IntMap.insert (getFilePathId id) path idToPathMap) (HMS.insert (artifactFilePath path) id pathToIdMap)
+  where
+    insertPathId :: ArtifactsLocation -> FilePathId -> PathIdMap -> PathIdMap
+    insertPathId path id PathIdMap{..} =
+        PathIdMap
+            (IntMap.insert (getFilePathId id) path idToPathMap)
+            (HMS.insert (artifactFilePath path) id pathToIdMap)
+            (succ nextFreshId)
 
 insertImport :: FilePathId -> Either ModuleParseError ModuleImports -> RawDependencyInformation -> RawDependencyInformation
 insertImport (FilePathId k) v rawDepInfo = rawDepInfo { rawImports = IntMap.insert k v (rawImports rawDepInfo) }