Support for Pattern Synonyms

src/Haskell/Ide/Engine/Plugin/GhcMod.hs

@@ -681,21 +681,30 @@ symbolProvider uri = pluginGetFile "ghc-mod symbolProvider: " uri $
         goValD (L l (PatBind { pat_lhs = p })) =
           map (\n -> Decl LSP.SkVariable n [] l) $ hsNamessRdr p
 
+#if __GLASGOW_HASKELL__ >= 806
+        goValD (L l (PatSynBind _ idR)) = case idR of
+          XPatSynBind _ -> error "xPatSynBind"
+          PSB { psb_id = ln } ->
+#else
+        goValD (L l (PatSynBind (PSB { psb_id = ln }))) =
+#endif
+            -- We are reporting pattern synonyms as functions. There is no such
+            -- thing as pattern synonym in current LSP specification so we pick up
+            -- an (arguably) closest match.
+            pure (Decl LSP.SkFunction ln [] l)
+
 #if __GLASGOW_HASKELL__ >= 806
         goValD (L _ (FunBind _ _ (XMatchGroup _) _ _)) = error "goValD"
         goValD (L _ (VarBind _ _ _ _))                 = error "goValD"
         goValD (L _ (AbsBinds _ _ _ _ _ _ _))          = error "goValD"
-        goValD (L _ (PatSynBind _ _))                  = error "goValD"
         goValD (L _ (XHsBindsLR _))                    = error "goValD"
 #elif __GLASGOW_HASKELL__ >= 804
         goValD (L _ (VarBind _ _ _))        = error "goValD"
         goValD (L _ (AbsBinds _ _ _ _ _ _)) = error "goValD"
-        goValD (L _ (PatSynBind _))         = error "goValD"
 #else
         goValD (L _ (VarBind _ _ _))           = error "goValD"
         goValD (L _ (AbsBinds _ _ _ _ _))      = error "goValD"
         goValD (L _ (AbsBindsSig _ _ _ _ _ _)) = error "goValD"
-        goValD (L _ (PatSynBind _))            = error "goValD"
 #endif
 
         -- -----------------------------

test/functional/SymbolsSpec.hs

@@ -12,20 +12,22 @@ spec :: Spec
 spec = describe "document symbols" $ do
 
   -- Some common ranges and selection ranges in Symbols.hs
-  let fooSR = Range (Position 4 0) (Position 4 3)
-      fooR  = Range (Position 4 0) (Position 6 43)
-      barSR = Range (Position 5 8) (Position 5 11)
-      barR  = Range (Position 5 8) (Position 6 43)
-      dogSR = Range (Position 6 17) (Position 6 20)
-      dogR  = Range (Position 6 16) (Position 6 43)
-      catSR = Range (Position 6 22) (Position 6 25)
-      catR  = Range (Position 6 16) (Position 6 43)
-      myDataSR = Range (Position 8 5) (Position 8 11)
-      myDataR  = Range (Position 8 0) (Position 9 22)
-      aSR = Range (Position 8 14) (Position 8 15)
-      aR  = Range (Position 8 14) (Position 8 19)
-      bSR = Range (Position 9 14) (Position 9 15)
-      bR  = Range (Position 9 14) (Position 9 22)
+  let fooSR = Range (Position 5 0) (Position 5 3)
+      fooR  = Range (Position 5 0) (Position 7 43)
+      barSR = Range (Position 6 8) (Position 6 11)
+      barR  = Range (Position 6 8) (Position 7 43)
+      dogSR = Range (Position 7 17) (Position 7 20)
+      dogR  = Range (Position 7 16) (Position 7 43)
+      catSR = Range (Position 7 22) (Position 7 25)
+      catR  = Range (Position 7 16) (Position 7 43)
+      myDataSR = Range (Position 9 5) (Position 9 11)
+      myDataR  = Range (Position 9 0) (Position 10 22)
+      aSR = Range (Position 9 14) (Position 9 15)
+      aR  = Range (Position 9 14) (Position 9 19)
+      bSR = Range (Position 10 14) (Position 10 15)
+      bR  = Range (Position 10 14) (Position 10 22)
+      testPatternSR = Range (Position 13 8) (Position 13 19)
+      testPatternR = Range (Position 13 0) (Position 13 27)
 
   describe "3.10 hierarchical document symbols" $ do
     it "provides nested data types and constructors" $ runSession hieCommand fullCaps "test/testdata" $ do
@@ -48,6 +50,14 @@ spec = describe "document symbols" $ do
           cat = DocumentSymbol "cat" (Just "") SkVariable Nothing catR catSR (Just mempty)
 
       liftIO $ symbs `shouldContain` [foo]
+    it "provides pattern synonyms" $ runSession hieCommand fullCaps "test/testdata" $ do
+      doc <- openDoc "Symbols.hs" "haskell"
+      Left symbs <- getDocumentSymbols doc
+
+      let testPattern = DocumentSymbol "TestPattern"
+            (Just "") SkFunction Nothing testPatternR testPatternSR (Just mempty)
+
+      liftIO $ symbs `shouldContain` [testPattern]
 
     -- TODO: Test module, imports
 

test/testdata/Symbols.hs

@@ -1,3 +1,4 @@
+{-# LANGUAGE PatternSynonyms #-}
 module Symbols where
 
 import Data.Maybe
@@ -8,3 +9,6 @@ foo = bar
 
 data MyData = A Int
             | B String
+
+pattern TestPattern :: Int -> MyData
+pattern TestPattern x = A x