Use edit-distannce instead of handrolling

Author: crtschin

ghcide/ghcide.cabal

@@ -60,6 +60,7 @@ library
     , Diff                         ^>=0.5 || ^>=1.0.0
     , directory
     , dlist
+    , edit-distance
     , enummapset
     , exceptions
     , extra                        >=1.7.14
@@ -83,7 +84,6 @@ library
     , list-t
     , lsp                          ^>=2.7
     , lsp-types                    ^>=2.3
-    , MemoTrie
     , mtl
     , opentelemetry                >=0.6.1
     , optparse-applicative

ghcide/src/Text/Fuzzy/Levenshtein.hs

@@ -1,36 +1,16 @@
 module Text.Fuzzy.Levenshtein where
 
-import           Data.Function       (fix)
 import           Data.List           (sortOn)
-import           Data.MemoTrie
+import           Data.Text           (Text)
 import qualified Data.Text           as T
-import qualified Data.Text.Array     as T
-import           Data.Text.Internal  (Text (..))
+import           Text.EditDistance
 import           Text.Fuzzy.Parallel
 
--- | Same caveats apply w.r.t. ASCII as in 'Text.Fuzzy.Parallel'.
--- Might be worth optimizing this at some point, but it's good enoughᵗᵐ for now
-levenshtein :: Text -> Text -> Int
-levenshtein a b | T.null a = T.length b
-levenshtein a b | T.null b = T.length a
-levenshtein (Text aBuf aOff aLen) (Text bBuf bOff bLen) = do
-  let aTot = aOff + aLen
-      bTot = bOff + bLen
-      go' _ (!aIx, !bIx) | aIx >= aTot || bIx >= bTot = max (aTot - aIx) (bTot - bIx)
-      go' f (!aIx, !bIx) | T.unsafeIndex aBuf aIx == T.unsafeIndex bBuf bIx = f (aIx + 1, bIx + 1)
-      go' f (!aIx, !bIx) =
-        minimum
-          [ 2 + f (aIx + 1, bIx + 1), -- Give substitutions a heavier cost, so multiple typos cost more
-            1 + f (aIx + 1, bIx),
-            1 + f (aIx, bIx + 1)
-          ]
-      go = fix (memo . go')
-  go (aOff, bOff)
-
 -- | Sort the given list according to it's levenshtein distance relative to the
 -- given string.
 levenshteinScored :: Int -> Text -> [Text] -> [Scored Text]
-levenshteinScored chunkSize needle haystack =
+levenshteinScored chunkSize needle haystack = do
+  let levenshtein = levenshteinDistance $ defaultEditCosts {substitutionCosts=ConstantCost 2}
   sortOn score $
     matchPar chunkSize needle haystack id $
-      \a b -> Just $ levenshtein a b
+      \a b -> Just $ levenshtein (T.unpack a) (T.unpack b)