From bb5aa2c854b0d8ae6629276c448ddfdbbf097726 Mon Sep 17 00:00:00 2001
From: "Carsten Csiky (csicar)" <carsten.csiky@gmail.com>
Date: Fri, 16 Aug 2019 03:08:19 +0200
Subject: [PATCH 1/5] Suggest import for name causing a UnknownName error

---
 src/Language/PureScript/AST/Declarations.hs |  1 +
 src/Language/PureScript/Errors.hs           | 21 ++++++++---
 src/Language/PureScript/Make.hs             |  4 ++-
 src/Language/PureScript/Suggest.hs          | 39 +++++++++++++++++++++
 4 files changed, 59 insertions(+), 6 deletions(-)
 create mode 100644 src/Language/PureScript/Suggest.hs

diff --git a/src/Language/PureScript/AST/Declarations.hs b/src/Language/PureScript/AST/Declarations.hs
index 93f8d879e5..0cce4de85d 100644
--- a/src/Language/PureScript/AST/Declarations.hs
+++ b/src/Language/PureScript/AST/Declarations.hs
@@ -205,6 +205,7 @@ data ErrorMessageHint
   | ErrorInTypeClassDeclaration (ProperName 'ClassName)
   | ErrorInForeignImport Ident
   | ErrorSolvingConstraint SourceConstraint
+  | ErrorMissingImport (NEL.NonEmpty (ModuleName, DeclarationRef)) -- List of possible import matching the expected name
   | PositionedError (NEL.NonEmpty SourceSpan)
   deriving (Show)
 
diff --git a/src/Language/PureScript/Errors.hs b/src/Language/PureScript/Errors.hs
index cb4f460952..f2f5a45ac3 100644
--- a/src/Language/PureScript/Errors.hs
+++ b/src/Language/PureScript/Errors.hs
@@ -338,12 +338,12 @@ errorSuggestion err =
     emptySuggestion = Just $ ErrorSuggestion ""
     suggest = Just . ErrorSuggestion
 
-    importSuggestion :: ModuleName -> [ DeclarationRef ] -> Maybe ModuleName -> Text
-    importSuggestion mn refs qual =
-      "import " <> runModuleName mn <> " (" <> T.intercalate ", " (mapMaybe prettyPrintRef refs) <> ")" <> qstr qual
-
+importSuggestion :: ModuleName -> [ DeclarationRef ] -> Maybe ModuleName -> Text
+importSuggestion mn refs qual =
+    "import " <> runModuleName mn <> " (" <> T.intercalate ", " (mapMaybe prettyPrintRef refs) <> ")" <> qstr qual
+  where
     qstr :: Maybe ModuleName -> Text
-    qstr (Just mn) = " as " <> runModuleName mn
+    qstr (Just moduleName) = " as " <> runModuleName moduleName
     qstr Nothing = ""
 
 suggestionSpan :: ErrorMessage -> Maybe SourceSpan
@@ -1185,6 +1185,17 @@ prettyPrintSingleError (PPEOptions codeColor full level showDocs relPath) e = fl
       paras [ line $ "at " <> displaySourceSpan relPath (NEL.head srcSpan)
             , detail
             ]
+    renderHint (ErrorMissingImport importOptions) detail =
+      paras [ detail
+            , line $ "Perhaps you want to add it to the import list? " <> message
+            , markCodeBox $ indent $ Box.vcat Box.left $ (line . renderImport) <$> importOptions
+            ]
+      where
+        renderImport (mn, (ReExportRef _ _ ref)) = importSuggestion mn [ref] Nothing
+        renderImport (mn, ref) = importSuggestion mn [ref] Nothing
+        message = case length importOptions of
+          1 -> "1 possible import was found:"
+          n -> T.pack (show n) <> " possible imports were found:"
 
     printRow :: (Int -> Type a -> Box.Box) -> Type a -> Box.Box
     printRow f t = markCodeBox $ indent $ f prettyDepth t
diff --git a/src/Language/PureScript/Make.hs b/src/Language/PureScript/Make.hs
index f983266420..7db95a43db 100644
--- a/src/Language/PureScript/Make.hs
+++ b/src/Language/PureScript/Make.hs
@@ -34,6 +34,7 @@ import           Language.PureScript.Environment
 import           Language.PureScript.Errors
 import           Language.PureScript.Externs
 import           Language.PureScript.Linter
+import           Language.PureScript.Suggest
 import           Language.PureScript.ModuleDependencies
 import           Language.PureScript.Names
 import           Language.PureScript.Renamer
@@ -125,7 +126,8 @@ make ma@MakeActions{..} ms = do
   results <- BuildPlan.collectResults buildPlan
 
   -- All threads have completed, rethrow any caught errors.
-  let errors = mapMaybe buildJobFailure $ M.elems results
+  let errors = decorateSuggestions (M.elems results) $ mapMaybe buildJobFailure $ M.elems results
+  
   unless (null errors) $ throwError (mconcat errors)
 
   -- Here we return all the ExternsFile in the ordering of the topological sort,
diff --git a/src/Language/PureScript/Suggest.hs b/src/Language/PureScript/Suggest.hs
new file mode 100644
index 0000000000..18e72e01ff
--- /dev/null
+++ b/src/Language/PureScript/Suggest.hs
@@ -0,0 +1,39 @@
+-- |
+-- This module implements a simple linting pass on the PureScript AST.
+--
+module Language.PureScript.Suggest where
+
+import Prelude.Compat
+
+import Data.Maybe (catMaybes, maybeToList)
+
+import qualified Data.List.NonEmpty as NEL
+
+import Language.PureScript.Make.BuildPlan
+import           Language.PureScript.Errors
+import           Language.PureScript.Externs
+import Language.PureScript.Names
+
+
+decorateSuggestions :: [BuildJobResult] -> [MultipleErrors] -> [MultipleErrors]
+decorateSuggestions jobs multipleErrors = decorateMultipleErrors <$> multipleErrors
+    where
+      compiledExterns :: [ExternsFile]
+      compiledExterns = snd <$> (catMaybes $ buildJobSuccess <$> jobs)
+
+      decorateMultipleErrors :: MultipleErrors -> MultipleErrors
+      decorateMultipleErrors (MultipleErrors errs) = MultipleErrors $ decorateErrorMessage <$> errs
+
+      decorateErrorMessage :: ErrorMessage -> ErrorMessage
+      decorateErrorMessage (ErrorMessage hints err@(UnknownName (Qualified Nothing name))) = ErrorMessage (hints ++ maybeToList (importHintsForModule name)) err
+      decorateErrorMessage others = others
+
+      importHintsForModule :: Name -> Maybe ErrorMessageHint
+      importHintsForModule name = ErrorMissingImport <$> NEL.nonEmpty qualifiedValues 
+        where qualifiedValues = findImportForName name 
+
+      findImportForName :: Name -> [(ModuleName, DeclarationRef)]
+      findImportForName name = 
+        filter ((==name) . declRefName . snd)
+        $ concat
+        $ (\extern -> (\decl -> (efModuleName extern, decl)) <$> efExports extern) <$> compiledExterns
\ No newline at end of file

From a9eeb77ab73f7f5bdd4a092968051b18ca52e2d6 Mon Sep 17 00:00:00 2001
From: "Carsten Csiky (csicar)" <carsten.csiky@gmail.com>
Date: Sun, 18 Aug 2019 11:59:29 +0200
Subject: [PATCH 2/5] move suggestion to SimpleError instead of Hint

---
 src/Language/PureScript/AST/Declarations.hs   |  4 ++--
 src/Language/PureScript/Errors.hs             | 21 +++++++------------
 src/Language/PureScript/Sugar/Names.hs        |  4 ++--
 src/Language/PureScript/Sugar/Names/Env.hs    |  2 +-
 .../PureScript/Sugar/Names/Imports.hs         |  2 +-
 src/Language/PureScript/Sugar/Operators.hs    |  6 +++---
 src/Language/PureScript/Sugar/TypeClasses.hs  |  2 +-
 src/Language/PureScript/Suggest.hs            |  8 +++----
 src/Language/PureScript/TypeChecker/Kinds.hs  |  2 +-
 src/Language/PureScript/TypeChecker/Types.hs  |  6 +++---
 10 files changed, 25 insertions(+), 32 deletions(-)

diff --git a/src/Language/PureScript/AST/Declarations.hs b/src/Language/PureScript/AST/Declarations.hs
index 0cce4de85d..5fc08867ae 100644
--- a/src/Language/PureScript/AST/Declarations.hs
+++ b/src/Language/PureScript/AST/Declarations.hs
@@ -85,7 +85,8 @@ data SimpleErrorMessage
   | OrphanTypeDeclaration Ident
   | RedefinedIdent Ident
   | OverlappingNamesInLet
-  | UnknownName (Qualified Name)
+  | UnknownName [(ModuleName, DeclarationRef)] (Qualified Name)
+  -- ^ possible imports (filled with values in Make); missing name
   | UnknownImport ModuleName Name
   | UnknownImportDataConstructor ModuleName (ProperName 'TypeName) (ProperName 'ConstructorName)
   | UnknownExport Name
@@ -205,7 +206,6 @@ data ErrorMessageHint
   | ErrorInTypeClassDeclaration (ProperName 'ClassName)
   | ErrorInForeignImport Ident
   | ErrorSolvingConstraint SourceConstraint
-  | ErrorMissingImport (NEL.NonEmpty (ModuleName, DeclarationRef)) -- List of possible import matching the expected name
   | PositionedError (NEL.NonEmpty SourceSpan)
   deriving (Show)
 
diff --git a/src/Language/PureScript/Errors.hs b/src/Language/PureScript/Errors.hs
index f2f5a45ac3..21da2b5e4e 100644
--- a/src/Language/PureScript/Errors.hs
+++ b/src/Language/PureScript/Errors.hs
@@ -333,6 +333,7 @@ errorSuggestion err =
       HidingImport mn refs -> suggest $ importSuggestion mn refs Nothing
       MissingTypeDeclaration ident ty -> suggest $ showIdent ident <> " :: " <> T.pack (prettyPrintSuggestedType ty)
       WildcardInferredType ty _ -> suggest $ T.pack (prettyPrintSuggestedType ty)
+      UnknownName alternatives unknownName -> suggest $ T.unlines $ (\(mn, ref) -> importSuggestion mn [ref] Nothing) <$> alternatives
       _ -> Nothing
   where
     emptySuggestion = Just $ ErrorSuggestion ""
@@ -534,10 +535,12 @@ prettyPrintSingleError (PPEOptions codeColor full level showDocs relPath) e = fl
       line $ "The type declaration for " <> markCode (showIdent nm) <> " should be followed by its definition."
     renderSimpleErrorMessage (RedefinedIdent name) =
       line $ "The value " <> markCode (showIdent name) <> " has been defined multiple times"
-    renderSimpleErrorMessage (UnknownName name@(Qualified Nothing (IdentName (Ident i)))) | i `elem` [ C.bind, C.discard ] =
+    renderSimpleErrorMessage (UnknownName _ name@(Qualified Nothing (IdentName (Ident i)))) | i `elem` [ C.bind, C.discard ] =
       line $ "Unknown " <> printName name <> ". You're probably using do-notation, which the compiler replaces with calls to the " <> markCode i <> " function. Please import " <> markCode i <> " from module " <> markCode "Prelude"
-    renderSimpleErrorMessage (UnknownName name) =
-      line $ "Unknown " <> printName name
+    renderSimpleErrorMessage msg@(UnknownName _ name) =
+      paras [ line $ "Unknown " <> printName name
+            , indent $ line $ markCode $ showSuggestion msg
+            ]
     renderSimpleErrorMessage (UnknownImport mn name) =
       paras [ line $ "Cannot import " <> printName (Qualified Nothing name) <> " from module " <> markCode (runModuleName mn)
             , line "It either does not exist or the module does not export it."
@@ -1185,17 +1188,7 @@ prettyPrintSingleError (PPEOptions codeColor full level showDocs relPath) e = fl
       paras [ line $ "at " <> displaySourceSpan relPath (NEL.head srcSpan)
             , detail
             ]
-    renderHint (ErrorMissingImport importOptions) detail =
-      paras [ detail
-            , line $ "Perhaps you want to add it to the import list? " <> message
-            , markCodeBox $ indent $ Box.vcat Box.left $ (line . renderImport) <$> importOptions
-            ]
-      where
-        renderImport (mn, (ReExportRef _ _ ref)) = importSuggestion mn [ref] Nothing
-        renderImport (mn, ref) = importSuggestion mn [ref] Nothing
-        message = case length importOptions of
-          1 -> "1 possible import was found:"
-          n -> T.pack (show n) <> " possible imports were found:"
+      
 
     printRow :: (Int -> Type a -> Box.Box) -> Type a -> Box.Box
     printRow f t = markCodeBox $ indent $ f prettyDepth t
diff --git a/src/Language/PureScript/Sugar/Names.hs b/src/Language/PureScript/Sugar/Names.hs
index fcf7f469d3..2e199b55a0 100644
--- a/src/Language/PureScript/Sugar/Names.hs
+++ b/src/Language/PureScript/Sugar/Names.hs
@@ -419,11 +419,11 @@ renameInModule imports (Module modSS coms mn decls exps) =
       (Nothing, Just mn'') ->
         if mn'' `S.member` importedQualModules imports || mn'' `S.member` importedModules imports
         then throwUnknown
-        else throwError . errorMessage . UnknownName . Qualified Nothing $ ModName mn''
+        else throwError . errorMessage . UnknownName [] . Qualified Nothing $ ModName mn''
 
       -- If neither of the above cases are true then it's an undefined or
       -- unimported symbol.
       _ -> throwUnknown
 
     where
-    throwUnknown = throwError . errorMessage . UnknownName . fmap toName $ qname
+    throwUnknown = throwError . errorMessage . UnknownName [] . fmap toName $ qname
diff --git a/src/Language/PureScript/Sugar/Names/Env.hs b/src/Language/PureScript/Sugar/Names/Env.hs
index 31a109ba0e..594b9ee927 100644
--- a/src/Language/PureScript/Sugar/Names/Env.hs
+++ b/src/Language/PureScript/Sugar/Names/Env.hs
@@ -485,7 +485,7 @@ throwExportConflict' ss new existing newName existingName =
 getExports :: MonadError MultipleErrors m => Env -> ModuleName -> m Exports
 getExports env mn =
   maybe
-    (throwError . errorMessage . UnknownName . Qualified Nothing $ ModName mn)
+    (throwError . errorMessage . UnknownName [] . Qualified Nothing $ ModName mn)
     (return . envModuleExports)
   $ M.lookup mn env
 
diff --git a/src/Language/PureScript/Sugar/Names/Imports.hs b/src/Language/PureScript/Sugar/Names/Imports.hs
index 4253709055..46dd3968a7 100644
--- a/src/Language/PureScript/Sugar/Names/Imports.hs
+++ b/src/Language/PureScript/Sugar/Names/Imports.hs
@@ -70,7 +70,7 @@ resolveModuleImport env ie (mn, imps) = foldM go ie imps
   go ie' (ss, typ, impQual) = do
     modExports <-
       maybe
-        (throwError . errorMessage' ss . UnknownName . Qualified Nothing $ ModName mn)
+        (throwError . errorMessage' ss . UnknownName [] . Qualified Nothing $ ModName mn)
         (return . envModuleExports)
         (mn `M.lookup` env)
     let impModules = importedModules ie'
diff --git a/src/Language/PureScript/Sugar/Operators.hs b/src/Language/PureScript/Sugar/Operators.hs
index 1d0bb8aec4..19018de262 100644
--- a/src/Language/PureScript/Sugar/Operators.hs
+++ b/src/Language/PureScript/Sugar/Operators.hs
@@ -149,7 +149,7 @@ rebracketFiltered pred_ externs modules = do
         Just (Qualified mn' (Right alias)) ->
           return $ Constructor pos (Qualified mn' alias)
         Nothing ->
-          throwError . errorMessage' pos . UnknownName $ fmap ValOpName op
+          throwError . errorMessage' pos . UnknownName [] $ fmap ValOpName op
     goExpr pos other = return (pos, other)
 
     goBinder :: SourceSpan -> Binder -> m (SourceSpan, Binder)
@@ -161,7 +161,7 @@ rebracketFiltered pred_ externs modules = do
         Just (Qualified mn' (Right alias)) ->
           return (pos, ConstructorBinder pos (Qualified mn' alias) [lhs, rhs])
         Nothing ->
-          throwError . errorMessage' pos . UnknownName $ fmap ValOpName op
+          throwError . errorMessage' pos . UnknownName [] $ fmap ValOpName op
     goBinder _ BinaryNoParensBinder{} =
       internalError "BinaryNoParensBinder has no OpBinder"
     goBinder pos other = return (pos, other)
@@ -172,7 +172,7 @@ rebracketFiltered pred_ externs modules = do
         Just alias ->
           return $ TypeApp ann (TypeApp ann (TypeConstructor ann2 alias) lhs) rhs
         Nothing ->
-          throwError . errorMessage' pos $ UnknownName $ fmap TyOpName op
+          throwError . errorMessage' pos $ UnknownName [] $ fmap TyOpName op
     goType _ other = return other
 
 rebracketModule
diff --git a/src/Language/PureScript/Sugar/TypeClasses.hs b/src/Language/PureScript/Sugar/TypeClasses.hs
index 761de6f631..4ed71411b6 100644
--- a/src/Language/PureScript/Sugar/TypeClasses.hs
+++ b/src/Language/PureScript/Sugar/TypeClasses.hs
@@ -303,7 +303,7 @@ typeInstanceDictionaryDeclaration sa@(ss, _) name mn deps className tys decls =
 
   -- Lookup the type arguments and member types for the type class
   TypeClassData{..} <-
-    maybe (throwError . errorMessage' ss . UnknownName $ fmap TyClassName className) return $
+    maybe (throwError . errorMessage' ss . UnknownName [] $ fmap TyClassName className) return $
       M.lookup (qualify mn className) m
 
   -- Replace the type arguments with the appropriate types in the member types
diff --git a/src/Language/PureScript/Suggest.hs b/src/Language/PureScript/Suggest.hs
index 18e72e01ff..31ae8be8ee 100644
--- a/src/Language/PureScript/Suggest.hs
+++ b/src/Language/PureScript/Suggest.hs
@@ -25,12 +25,12 @@ decorateSuggestions jobs multipleErrors = decorateMultipleErrors <$> multipleErr
       decorateMultipleErrors (MultipleErrors errs) = MultipleErrors $ decorateErrorMessage <$> errs
 
       decorateErrorMessage :: ErrorMessage -> ErrorMessage
-      decorateErrorMessage (ErrorMessage hints err@(UnknownName (Qualified Nothing name))) = ErrorMessage (hints ++ maybeToList (importHintsForModule name)) err
+      decorateErrorMessage (ErrorMessage hints err) = ErrorMessage hints (suggestionForSimpleError err)
       decorateErrorMessage others = others
 
-      importHintsForModule :: Name -> Maybe ErrorMessageHint
-      importHintsForModule name = ErrorMissingImport <$> NEL.nonEmpty qualifiedValues 
-        where qualifiedValues = findImportForName name 
+      suggestionForSimpleError ::  SimpleErrorMessage -> SimpleErrorMessage
+      suggestionForSimpleError (UnknownName imports qualName@(Qualified Nothing name)) = UnknownName (imports ++ findImportForName name) qualName
+      suggestionForSimpleError others = others
 
       findImportForName :: Name -> [(ModuleName, DeclarationRef)]
       findImportForName name = 
diff --git a/src/Language/PureScript/TypeChecker/Kinds.hs b/src/Language/PureScript/TypeChecker/Kinds.hs
index 28a4009b52..6fe00611ba 100644
--- a/src/Language/PureScript/TypeChecker/Kinds.hs
+++ b/src/Language/PureScript/TypeChecker/Kinds.hs
@@ -251,7 +251,7 @@ infer' other = (, []) <$> go other
   go (TypeConstructor ann v) = do
     env <- getEnv
     case M.lookup v (types env) of
-      Nothing -> throwError . errorMessage' (fst ann) . UnknownName $ fmap TyName v
+      Nothing -> throwError . errorMessage' (fst ann) . UnknownName [] $ fmap TyName v
       Just (kind, _) -> return $ kind $> ann
   go (TypeApp ann t1 t2) = do
     k0 <- freshKind ann
diff --git a/src/Language/PureScript/TypeChecker/Types.hs b/src/Language/PureScript/TypeChecker/Types.hs
index e4491359f2..e85891e051 100644
--- a/src/Language/PureScript/TypeChecker/Types.hs
+++ b/src/Language/PureScript/TypeChecker/Types.hs
@@ -387,7 +387,7 @@ infer' (Var ss var) = do
 infer' v@(Constructor _ c) = do
   env <- getEnv
   case M.lookup c (dataConstructors env) of
-    Nothing -> throwError . errorMessage . UnknownName . fmap DctorName $ c
+    Nothing -> throwError . errorMessage . UnknownName [] . fmap DctorName $ c
     Just (_, _, ty, _) -> do (v', ty') <- sndM (introduceSkolemScope <=< replaceAllTypeSynonyms) <=< instantiatePolyTypeWithUnknowns v $ ty
                              return $ TypedValue' True v' ty'
 infer' (Case vals binders) = do
@@ -495,7 +495,7 @@ inferBinder val (ConstructorBinder ss ctor binders) = do
       unless (expected == actual) . throwError . errorMessage' ss $ IncorrectConstructorArity ctor expected actual
       unifyTypes ret val
       M.unions <$> zipWithM inferBinder (reverse args) binders
-    _ -> throwError . errorMessage' ss . UnknownName . fmap DctorName $ ctor
+    _ -> throwError . errorMessage' ss . UnknownName [] . fmap DctorName $ ctor
   where
   peelArgs :: Type a -> ([Type a], Type a)
   peelArgs = go []
@@ -731,7 +731,7 @@ check' (Accessor prop val) ty = withErrorMessageHint (ErrorCheckingAccessor val
 check' v@(Constructor _ c) ty = do
   env <- getEnv
   case M.lookup c (dataConstructors env) of
-    Nothing -> throwError . errorMessage . UnknownName . fmap DctorName $ c
+    Nothing -> throwError . errorMessage . UnknownName [] . fmap DctorName $ c
     Just (_, _, ty1, _) -> do
       repl <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
       ty' <- introduceSkolemScope ty

From 1fec7418bba0a093ea8a620fb10b1b5cf7811596 Mon Sep 17 00:00:00 2001
From: "Carsten Csiky (csicar)" <carsten.csiky@gmail.com>
Date: Tue, 20 Aug 2019 12:09:36 +0200
Subject: [PATCH 3/5] use wildcard for unused variable

---
 src/Language/PureScript/Errors.hs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Language/PureScript/Errors.hs b/src/Language/PureScript/Errors.hs
index 21da2b5e4e..e6066bd3d6 100644
--- a/src/Language/PureScript/Errors.hs
+++ b/src/Language/PureScript/Errors.hs
@@ -333,7 +333,7 @@ errorSuggestion err =
       HidingImport mn refs -> suggest $ importSuggestion mn refs Nothing
       MissingTypeDeclaration ident ty -> suggest $ showIdent ident <> " :: " <> T.pack (prettyPrintSuggestedType ty)
       WildcardInferredType ty _ -> suggest $ T.pack (prettyPrintSuggestedType ty)
-      UnknownName alternatives unknownName -> suggest $ T.unlines $ (\(mn, ref) -> importSuggestion mn [ref] Nothing) <$> alternatives
+      UnknownName alternatives _ -> suggest $ T.unlines $ (\(mn, ref) -> importSuggestion mn [ref] Nothing) <$> alternatives
       _ -> Nothing
   where
     emptySuggestion = Just $ ErrorSuggestion ""

From be52fb956facf1d1504072e748d65c65eb74831d Mon Sep 17 00:00:00 2001
From: "Carsten Csiky (csicar)" <carsten.csiky@gmail.com>
Date: Tue, 20 Aug 2019 12:36:39 +0200
Subject: [PATCH 4/5] `errorSuggestion` allows for multiple suggestions

Previously errorSuggestion returned `(Just "")` for UnusedImport and
DuplicateImport and `Nothing` for any other ErrorMessage that has no
suggestions. Both `Just ""` and `Nothing` seem to be treated the same
and represented as `""` in the rendered versions.

The matching imports suggestions for UnknownName now are represented as
seperate suggestions, which allow for proper rendering.

The JSON represenation of multiple suggestions is still a single string,
as changing that would require changing the JSON schema.
---
 src/Language/PureScript/Errors.hs      | 39 +++++++++++++-------------
 src/Language/PureScript/Errors/JSON.hs |  4 +--
 2 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/src/Language/PureScript/Errors.hs b/src/Language/PureScript/Errors.hs
index e6066bd3d6..63c88ceeea 100644
--- a/src/Language/PureScript/Errors.hs
+++ b/src/Language/PureScript/Errors.hs
@@ -319,11 +319,11 @@ errorDocUri e = "https://github.com/purescript/documentation/blob/master/errors/
 -- TODO Other possible suggestions:
 -- WildcardInferredType - source span not small enough
 -- DuplicateSelectiveImport - would require 2 ranges to remove and 1 insert
-errorSuggestion :: SimpleErrorMessage -> Maybe ErrorSuggestion
+errorSuggestion :: SimpleErrorMessage -> [ErrorSuggestion]
 errorSuggestion err =
     case err of
-      UnusedImport{} -> emptySuggestion
-      DuplicateImport{} -> emptySuggestion
+      UnusedImport{} -> []
+      DuplicateImport{} -> []
       UnusedExplicitImport mn _ qual refs -> suggest $ importSuggestion mn refs qual
       UnusedDctorImport mn _ qual refs -> suggest $ importSuggestion mn refs qual
       UnusedDctorExplicitImport mn _ _ qual refs -> suggest $ importSuggestion mn refs qual
@@ -333,11 +333,14 @@ errorSuggestion err =
       HidingImport mn refs -> suggest $ importSuggestion mn refs Nothing
       MissingTypeDeclaration ident ty -> suggest $ showIdent ident <> " :: " <> T.pack (prettyPrintSuggestedType ty)
       WildcardInferredType ty _ -> suggest $ T.pack (prettyPrintSuggestedType ty)
-      UnknownName alternatives _ -> suggest $ T.unlines $ (\(mn, ref) -> importSuggestion mn [ref] Nothing) <$> alternatives
-      _ -> Nothing
+      UnknownName alternatives _ -> suggestMultiple $ (\(mn, ref) -> importSuggestionWithReexport mn ref) <$> alternatives
+      _ -> []
   where
-    emptySuggestion = Just $ ErrorSuggestion ""
-    suggest = Just . ErrorSuggestion
+    suggest a = [ErrorSuggestion a]
+    suggestMultiple = map ErrorSuggestion
+    importSuggestionWithReexport :: ModuleName -> DeclarationRef -> Text
+    importSuggestionWithReexport mn (ReExportRef _ _ ref) = importSuggestionWithReexport mn ref
+    importSuggestionWithReexport mn other = importSuggestion mn [other] Nothing
 
 importSuggestion :: ModuleName -> [ DeclarationRef ] -> Maybe ModuleName -> Text
 importSuggestion mn refs qual =
@@ -361,10 +364,8 @@ suggestionSpan e =
         MissingTypeDeclaration{} -> startOnly ss
         _ -> ss
 
-showSuggestion :: SimpleErrorMessage -> Text
-showSuggestion suggestion = case errorSuggestion suggestion of
-  Just (ErrorSuggestion x) -> x
-  _ -> ""
+showSuggestions :: SimpleErrorMessage -> [Text]
+showSuggestions suggestion = (\(ErrorSuggestion message) -> message) <$> errorSuggestion suggestion
 
 ansiColor :: (ANSI.ColorIntensity, ANSI.Color) -> String
 ansiColor (intesity, color) =
@@ -539,7 +540,7 @@ prettyPrintSingleError (PPEOptions codeColor full level showDocs relPath) e = fl
       line $ "Unknown " <> printName name <> ". You're probably using do-notation, which the compiler replaces with calls to the " <> markCode i <> " function. Please import " <> markCode i <> " from module " <> markCode "Prelude"
     renderSimpleErrorMessage msg@(UnknownName _ name) =
       paras [ line $ "Unknown " <> printName name
-            , indent $ line $ markCode $ showSuggestion msg
+            , indent $ Box.vcat Box.left $ line . markCode <$> showSuggestions msg
             ]
     renderSimpleErrorMessage (UnknownImport mn name) =
       paras [ line $ "Cannot import " <> printName (Qualified Nothing name) <> " from module " <> markCode (runModuleName mn)
@@ -907,20 +908,20 @@ prettyPrintSingleError (PPEOptions codeColor full level showDocs relPath) e = fl
       paras [ line $ "The import of module " <> markCode (runModuleName mn) <> " contains the following unused references:"
             , indent $ paras $ map (line . markCode . runName . Qualified Nothing) names
             , line "It could be replaced with:"
-            , indent $ line $ markCode $ showSuggestion msg ]
+            , indent $ Box.vcat Box.left $ line . markCode <$> showSuggestions msg ]
 
     renderSimpleErrorMessage msg@(UnusedDctorImport mn name _ _) =
       paras [line $ "The import of type " <> markCode (runProperName name)
                     <> " from module " <> markCode (runModuleName mn) <> " includes data constructors but only the type is used"
             , line "It could be replaced with:"
-            , indent $ line $ markCode $ showSuggestion msg ]
+            , indent $ Box.vcat Box.left $ line . markCode <$> showSuggestions msg ]
 
     renderSimpleErrorMessage msg@(UnusedDctorExplicitImport mn name names _ _) =
       paras [ line $ "The import of type " <> markCode (runProperName name)
                      <> " from module " <> markCode (runModuleName mn) <> " includes the following unused data constructors:"
             , indent $ paras $ map (line . markCode . runProperName) names
             , line "It could be replaced with:"
-            , indent $ line $ markCode $ showSuggestion msg ]
+            , indent $ Box.vcat Box.left $ line . markCode <$> showSuggestions msg ]
 
     renderSimpleErrorMessage (DuplicateSelectiveImport name) =
       line $ "There is an existing import of " <> markCode (runModuleName name) <> ", consider merging the import lists"
@@ -941,22 +942,22 @@ prettyPrintSingleError (PPEOptions codeColor full level showDocs relPath) e = fl
     renderSimpleErrorMessage msg@(ImplicitQualifiedImport importedModule asModule _) =
       paras [ line $ "Module " <> markCode (runModuleName importedModule) <> " was imported as " <> markCode (runModuleName asModule) <> " with unspecified imports."
             , line $ "As there are multiple modules being imported as " <> markCode (runModuleName asModule) <> ", consider using the explicit form:"
-            , indent $ line $ markCode $ showSuggestion msg
+            , indent $ Box.vcat Box.left $ line . markCode <$> showSuggestions msg
             ]
     renderSimpleErrorMessage msg@(ImplicitQualifiedImportReExport importedModule asModule _) =
       paras [ line $ "Module " <> markCode (runModuleName importedModule) <> " was imported as " <> markCode (runModuleName asModule) <> " with unspecified imports."
             , line $ "As this module is being re-exported, consider using the explicit form:"
-            , indent $ line $ markCode $ showSuggestion msg
+            , indent $ Box.vcat Box.left $ line . markCode <$> showSuggestions msg
             ]
 
     renderSimpleErrorMessage msg@(ImplicitImport mn _) =
       paras [ line $ "Module " <> markCode (runModuleName mn) <> " has unspecified imports, consider using the explicit form: "
-            , indent $ line $ markCode $ showSuggestion msg
+            , indent $ Box.vcat Box.left $ line . markCode <$> showSuggestions msg
             ]
 
     renderSimpleErrorMessage msg@(HidingImport mn _) =
       paras [ line $ "Module " <> markCode (runModuleName mn) <> " has unspecified imports, consider using the inclusive form: "
-            , indent $ line $ markCode $ showSuggestion msg
+            , indent $ Box.vcat Box.left $ line . markCode <$> showSuggestions msg
             ]
 
     renderSimpleErrorMessage (CaseBinderLengthDiffers l bs) =
diff --git a/src/Language/PureScript/Errors/JSON.hs b/src/Language/PureScript/Errors/JSON.hs
index f552f91f03..43aae050e8 100644
--- a/src/Language/PureScript/Errors/JSON.hs
+++ b/src/Language/PureScript/Errors/JSON.hs
@@ -70,8 +70,8 @@ toJSONError verbose level e =
   toSuggestion :: P.ErrorMessage -> Maybe ErrorSuggestion
   toSuggestion em =
     case P.errorSuggestion $ P.unwrapErrorMessage em of
-      Nothing -> Nothing
-      Just s -> Just $ ErrorSuggestion (suggestionText s) (toErrorPosition <$> P.suggestionSpan em)
+      [] -> Nothing
+      s -> Just $ ErrorSuggestion (T.unlines $ suggestionText <$> s) (toErrorPosition <$> P.suggestionSpan em)
 
   -- TODO: Adding a newline because source spans chomp everything up to the next character
   suggestionText (P.ErrorSuggestion s) = if T.null s then s else s <> "\n"

From d94ae1c707dafc59b39bc040c6b96bd93194a69f Mon Sep 17 00:00:00 2001
From: "Carsten Csiky (csicar)" <carsten.csiky@gmail.com>
Date: Tue, 20 Aug 2019 12:47:05 +0200
Subject: [PATCH 5/5] rename showSuggestion and errorSuggestion to plural

to reflect the changed return type. Imports and shadowing were also
cleaned up.
---
 src/Language/PureScript/Errors.hs      | 6 +++---
 src/Language/PureScript/Errors/JSON.hs | 2 +-
 src/Language/PureScript/Suggest.hs     | 5 +----
 3 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/src/Language/PureScript/Errors.hs b/src/Language/PureScript/Errors.hs
index 63c88ceeea..5661fb1669 100644
--- a/src/Language/PureScript/Errors.hs
+++ b/src/Language/PureScript/Errors.hs
@@ -319,8 +319,8 @@ errorDocUri e = "https://github.com/purescript/documentation/blob/master/errors/
 -- TODO Other possible suggestions:
 -- WildcardInferredType - source span not small enough
 -- DuplicateSelectiveImport - would require 2 ranges to remove and 1 insert
-errorSuggestion :: SimpleErrorMessage -> [ErrorSuggestion]
-errorSuggestion err =
+errorSuggestions :: SimpleErrorMessage -> [ErrorSuggestion]
+errorSuggestions err =
     case err of
       UnusedImport{} -> []
       DuplicateImport{} -> []
@@ -365,7 +365,7 @@ suggestionSpan e =
         _ -> ss
 
 showSuggestions :: SimpleErrorMessage -> [Text]
-showSuggestions suggestion = (\(ErrorSuggestion message) -> message) <$> errorSuggestion suggestion
+showSuggestions simpleError = (\(ErrorSuggestion message) -> message) <$> errorSuggestions simpleError
 
 ansiColor :: (ANSI.ColorIntensity, ANSI.Color) -> String
 ansiColor (intesity, color) =
diff --git a/src/Language/PureScript/Errors/JSON.hs b/src/Language/PureScript/Errors/JSON.hs
index 43aae050e8..458179689d 100644
--- a/src/Language/PureScript/Errors/JSON.hs
+++ b/src/Language/PureScript/Errors/JSON.hs
@@ -69,7 +69,7 @@ toJSONError verbose level e =
                   (P.sourcePosColumn (P.spanEnd   ss))
   toSuggestion :: P.ErrorMessage -> Maybe ErrorSuggestion
   toSuggestion em =
-    case P.errorSuggestion $ P.unwrapErrorMessage em of
+    case P.errorSuggestions $ P.unwrapErrorMessage em of
       [] -> Nothing
       s -> Just $ ErrorSuggestion (T.unlines $ suggestionText <$> s) (toErrorPosition <$> P.suggestionSpan em)
 
diff --git a/src/Language/PureScript/Suggest.hs b/src/Language/PureScript/Suggest.hs
index 31ae8be8ee..e84393921d 100644
--- a/src/Language/PureScript/Suggest.hs
+++ b/src/Language/PureScript/Suggest.hs
@@ -5,9 +5,7 @@ module Language.PureScript.Suggest where
 
 import Prelude.Compat
 
-import Data.Maybe (catMaybes, maybeToList)
-
-import qualified Data.List.NonEmpty as NEL
+import Data.Maybe (catMaybes)
 
 import Language.PureScript.Make.BuildPlan
 import           Language.PureScript.Errors
@@ -26,7 +24,6 @@ decorateSuggestions jobs multipleErrors = decorateMultipleErrors <$> multipleErr
 
       decorateErrorMessage :: ErrorMessage -> ErrorMessage
       decorateErrorMessage (ErrorMessage hints err) = ErrorMessage hints (suggestionForSimpleError err)
-      decorateErrorMessage others = others
 
       suggestionForSimpleError ::  SimpleErrorMessage -> SimpleErrorMessage
       suggestionForSimpleError (UnknownName imports qualName@(Qualified Nothing name)) = UnknownName (imports ++ findImportForName name) qualName