Merge pull request #5186 from unisonweb/lsp/unused-binding-detection

unison-cli/src/Unison/LSP/Conversions.hs

@@ -49,3 +49,10 @@ annToRange = \case
   Ann.External -> Nothing
   Ann.GeneratedFrom a -> annToRange a
   Ann.Ann start end -> Just $ Range (uToLspPos start) (uToLspPos end)
+
+annToURange :: Ann.Ann -> Maybe Range.Range
+annToURange = \case
+  Ann.Intrinsic -> Nothing
+  Ann.External -> Nothing
+  Ann.GeneratedFrom a -> annToURange a
+  Ann.Ann start end -> Just $ Range.Range start end

unison-cli/src/Unison/LSP/FileAnalysis.hs

@@ -35,6 +35,7 @@ import Unison.KindInference.Error qualified as KindInference
 import Unison.LSP.Conversions
 import Unison.LSP.Conversions qualified as Cv
 import Unison.LSP.Diagnostics (DiagnosticSeverity (..), mkDiagnostic, reportDiagnostics)
+import Unison.LSP.FileAnalysis.UnusedBindings qualified as UnusedBindings
 import Unison.LSP.Orphans ()
 import Unison.LSP.Types
 import Unison.LSP.VFS qualified as VFS
@@ -111,12 +112,13 @@ checkFile doc = runMaybeT do
           & toRangeMap
   let typeSignatureHints = fromMaybe mempty (mkTypeSignatureHints <$> parsedFile <*> typecheckedFile)
   let fileSummary = FileSummary.mkFileSummary parsedFile typecheckedFile
+  let unusedBindingDiagnostics = fileSummary ^.. _Just . to termsBySymbol . folded . folding (\(topLevelAnn, _refId, trm, _type) -> UnusedBindings.analyseTerm fileUri topLevelAnn trm)
   let tokenMap = getTokenMap tokens
   conflictWarningDiagnostics <-
     fold <$> for fileSummary \fs ->
       lift $ computeConflictWarningDiagnostics fileUri fs
   let diagnosticRanges =
-        (errDiagnostics <> conflictWarningDiagnostics)
+        (errDiagnostics <> conflictWarningDiagnostics <> unusedBindingDiagnostics)
           & fmap (\d -> (d ^. range, d))
           & toRangeMap
   let fileAnalysis = FileAnalysis {diagnostics = diagnosticRanges, codeActions = codeActionRanges, fileSummary, typeSignatureHints, ..}

unison-cli/src/Unison/LSP/FileAnalysis/UnusedBindings.hs

@@ -0,0 +1,47 @@
+module Unison.LSP.FileAnalysis.UnusedBindings where
+
+import Data.Foldable qualified as Foldable
+import Data.Map qualified as Map
+import Data.Set qualified as Set
+import Data.Text qualified as Text
+import Language.LSP.Protocol.Types (Diagnostic)
+import Language.LSP.Protocol.Types qualified as Lsp
+import U.Core.ABT (ABT (..))
+import U.Core.ABT qualified as ABT
+import Unison.LSP.Conversions qualified as Cv
+import Unison.LSP.Diagnostics qualified as Diagnostic
+import Unison.Lexer.Pos qualified as Pos
+import Unison.Parser.Ann (Ann)
+import Unison.Prelude
+import Unison.Symbol (Symbol (..))
+import Unison.Term (Term)
+import Unison.Util.Range qualified as Range
+import Unison.Var qualified as Var
+
+analyseTerm :: Lsp.Uri -> Ann -> Term Symbol Ann -> [Diagnostic]
+analyseTerm fileUri topLevelTermAnn tm =
+  let (unusedVars, _) = ABT.cata alg tm
+   in Map.toList unusedVars & mapMaybe \(v, _ann) -> do
+        name <- getRelevantVarName v
+        -- Unfortunately we don't capture the annotation of the actual binding when parsing :'(, for now the least
+        -- annoying thing to do is just highlight the top of the binding.
+        urange <- Cv.annToURange topLevelTermAnn <&> (\(Range.Range start@(Pos.Pos line _col) _end) -> Range.Range start (Pos.Pos line 9999))
+        let lspRange = Cv.uToLspRange urange
+        pure $ Diagnostic.mkDiagnostic fileUri lspRange Diagnostic.DiagnosticSeverity_Warning ("Unused binding " <> tShow name <> " inside this term.\nUse the binding, or prefix it with an _ to dismiss this warning.") []
+  where
+    getRelevantVarName :: Symbol -> Maybe Text
+    getRelevantVarName = \case
+      -- We only care about user bindings which don't start with an underscore
+      Symbol _ (Var.User n) -> do
+        guard (not (Text.isPrefixOf "_" n))
+        pure n
+      _ -> Nothing
+    alg :: (Foldable f, Ord v) => Ann -> ABT f v (Map v Ann, Set v) -> (Map v Ann, Set v)
+    alg ann abt = case abt of
+      Var v -> (mempty, Set.singleton v)
+      Cycle x -> x
+      Abs v (unusedBindings, usedVars) ->
+        if v `Set.member` usedVars
+          then (unusedBindings, Set.delete v usedVars)
+          else (Map.insert v ann unusedBindings, usedVars)
+      Tm fx -> Foldable.fold fx

unison-cli/unison-cli.cabal

@@ -130,6 +130,7 @@ library
       Unison.LSP.Conversions
       Unison.LSP.Diagnostics
       Unison.LSP.FileAnalysis
+      Unison.LSP.FileAnalysis.UnusedBindings
       Unison.LSP.FoldingRange
       Unison.LSP.Formatting
       Unison.LSP.HandlerUtils