fix: include the field selector when looking for missing symbol

In GHC >= 9.8, the namespace for record selector changed and is now part
of a new namespace. This allows for duplicated record field names in the
same module.

This hence generated a few issues in HLS when looking for a symbol using
`lookupOccEnv`: the current implementation was only doing lookup in
type, data and var namespaces.

This commit uses `lookupOccEnv_AllNameSpaces`, so it may be more
efficient (one lookup instead of two), but it also incluse the symbols
from record field selectors and this will actually fix most import
suggestion logic when a record field selector is not found.

Note that the function is not available in `ghc` <= 9.6, hence the `CPP`
and fallsback implementation, which uses the previous implementation.

See https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.8#new-namespace-for-record-fields

Author: guibou

plugins/hls-refactor-plugin/src/Development/IDE/Plugin/CodeAction.hs

@@ -1476,8 +1476,6 @@ suggestNewOrExtendImportForClassMethod packageExportsMap ps fileContents Diagnos
 suggestNewImport :: DynFlags -> ExportsMap -> ParsedSource -> T.Text -> Diagnostic -> [(T.Text, CodeActionKind, TextEdit)]
 suggestNewImport df packageExportsMap ps fileContents Diagnostic{..}
   | msg <- unifySpaces _message
-  , Just thingMissing <- extractNotInScopeName msg
-  , qual <- extractQualifiedModuleName msg
   , qual' <-
       extractDoesNotExportModuleName msg
         >>= (findImportDeclByModuleName hsmodImports . T.unpack)
@@ -1574,13 +1572,34 @@ extractQualifiedModuleNameFromMissingName (T.strip -> missing)
         modNameP = fmap snd $ RE.withMatched $ conIDP `sepBy1` RE.sym '.'
 
 
+-- | A Backward compatible implementation of `lookupOccEnv_AllNameSpaces` for
+-- GHC <=9.6
+--
+-- It looks for a symbol name in all known namespaces, including types,
+-- variables, and fieldnames.
+--
+-- Note that on GHC >= 9.8, the record selectors are not in the `mkVarOrDataOcc`
+-- anymore, but are in a custom namespace, see
+-- https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.8#new-namespace-for-record-fields,
+-- hence we need to use this "AllNamespaces" implementation, otherwise we'll
+-- miss them.
+lookupOccEnvAllNamespaces :: ExportsMap -> T.Text -> [IdentInfo]
+#if MIN_VERSION_ghc(9,7,0)
+lookupOccEnvAllNamespaces exportsMap name = Set.toList $ mconcat (lookupOccEnv_AllNameSpaces (getExportsMap exportsMap) (mkTypeOcc name))
+#else
+lookupOccEnvAllNamespaces exportsMap name = maybe [] Set.toList $
+                            lookupOccEnv (getExportsMap exportsMap) (mkVarOrDataOcc name)
+                          <> lookupOccEnv (getExportsMap exportsMap) (mkTypeOcc name) -- look up the modified unknown name in the export map
+#endif
+
+
 constructNewImportSuggestions
   :: ExportsMap -> (Maybe T.Text, NotInScope) -> Maybe [T.Text] -> QualifiedImportStyle -> [ImportSuggestion]
 constructNewImportSuggestions exportsMap (qual, thingMissing) notTheseModules qis = nubOrdBy simpleCompareImportSuggestion
   [ suggestion
   | Just name <- [T.stripPrefix (maybe "" (<> ".") qual) $ notInScope thingMissing] -- strip away qualified module names from the unknown name
-  , identInfo <- maybe [] Set.toList $ lookupOccEnv (getExportsMap exportsMap) (mkVarOrDataOcc name)
-                                    <> lookupOccEnv (getExportsMap exportsMap) (mkTypeOcc name) -- look up the modified unknown name in the export map
+
+  , identInfo <- lookupOccEnvAllNamespaces exportsMap name -- look up the modified unknown name in the export map
   , canUseIdent thingMissing identInfo                                              -- check if the identifier information retrieved can be used
   , moduleNameText identInfo `notElem` fromMaybe [] notTheseModules                 -- check if the module of the identifier is allowed
   , suggestion <- renderNewImport identInfo                                         -- creates a list of import suggestions for the retrieved identifier information