1 files changed, 112 insertions, 8 deletions
diff --git a/compiler/GHC/Driver/Errors/Ppr.hs b/compiler/GHC/Driver/Errors/Ppr.hs
index 06ebe0be96..74c3d4bf21 100644
--- a/compiler/GHC/Driver/Errors/Ppr.hs
+++ b/compiler/GHC/Driver/Errors/Ppr.hs
@@ -5,11 +5,26 @@ module GHC.Driver.Errors.Ppr where
 
 import GHC.Prelude
 
-import GHC.Types.Error
 import GHC.Driver.Errors.Types
-import GHC.Parser.Errors.Ppr
-import GHC.Tc.Errors.Ppr ()
+import GHC.Driver.Flags
+import GHC.Driver.Session
 import GHC.HsToCore.Errors.Ppr ()
+import GHC.Parser.Errors.Ppr (pprPsError)
+import GHC.Tc.Errors.Ppr ()
+import GHC.Types.Error
+import GHC.Unit.Types
+import GHC.Utils.Outputable
+import GHC.Unit.Module
+
+--
+-- Suggestions
+--
+
+-- | Suggests a list of 'InstantiationSuggestion' for the '.hsig' file to the user.
+suggestInstantiatedWith :: ModuleName -> GenInstantiations UnitId -> [InstantiationSuggestion]
+suggestInstantiatedWith pi_mod_name insts =
+  [ InstantiationSuggestion k v | (k,v) <- ((pi_mod_name, mkHoleModule pi_mod_name) : insts) ]
+
 
 instance Diagnostic GhcMessage where
   diagnosticMessage = \case
@@ -37,9 +52,98 @@ instance Diagnostic GhcMessage where
       -> diagnosticReason m
 
 instance Diagnostic DriverMessage where
-  diagnosticMessage (DriverUnknownMessage m)  = diagnosticMessage m
-  diagnosticMessage (DriverPsHeaderMessage desc hints)
-    = mkSimpleDecorated $ pprPsError desc hints
+  diagnosticMessage = \case
+    DriverUnknownMessage m
+      -> diagnosticMessage m
+    DriverPsHeaderMessage desc hints
+      -> mkSimpleDecorated $ pprPsError desc hints
+    DriverMissingHomeModules missing buildingCabalPackage
+      -> let msg | buildingCabalPackage == YesBuildingCabalPackage
+                 = hang
+                     (text "These modules are needed for compilation but not listed in your .cabal file's other-modules: ")
+                     4
+                     (sep (map ppr missing))
+                 | otherwise
+                 =
+                   hang
+                     (text "Modules are not listed in command line but needed for compilation: ")
+                     4
+                     (sep (map ppr missing))
+         in mkSimpleDecorated msg
+    DriverUnusedPackages unusedArgs
+      -> let msg = vcat [ text "The following packages were specified" <+>
+                          text "via -package or -package-id flags,"
+                        , text "but were not needed for compilation:"
+                        , nest 2 (vcat (map (withDash . pprUnusedArg) unusedArgs))
+                        ]
+         in mkSimpleDecorated msg
+         where
+            withDash :: SDoc -> SDoc
+            withDash = (<+>) (text "-")
+
+            pprUnusedArg :: PackageArg -> SDoc
+            pprUnusedArg (PackageArg str) = text str
+            pprUnusedArg (UnitIdArg uid) = ppr uid
+    DriverUnnecessarySourceImports mod
+      -> mkSimpleDecorated (text "{-# SOURCE #-} unnecessary in import of " <+> quotes (ppr mod))
+    DriverDuplicatedModuleDeclaration mod files
+      -> mkSimpleDecorated $
+           text "module" <+> quotes (ppr mod) <+>
+           text "is defined in multiple files:" <+>
+           sep (map text files)
+    DriverModuleNotFound mod
+      -> mkSimpleDecorated (text "module" <+> quotes (ppr mod) <+> text "cannot be found locally")
+    DriverFileModuleNameMismatch actual expected
+      -> mkSimpleDecorated $
+           text "File name does not match module name:"
+           $$ text "Saw     :" <+> quotes (ppr actual)
+           $$ text "Expected:" <+> quotes (ppr expected)
 
-  diagnosticReason (DriverUnknownMessage m)   = diagnosticReason m
-  diagnosticReason (DriverPsHeaderMessage {}) = ErrorWithoutFlag
+    DriverUnexpectedSignature pi_mod_name buildingCabalPackage suggestions
+      -> let suggested_instantiated_with =
+               hcat (punctuate comma $
+                   [ ppr k <> text "=" <> ppr v
+                   | InstantiationSuggestion k v <- suggestions
+                   ])
+             msg = text "Unexpected signature:" <+> quotes (ppr pi_mod_name)
+                   $$ if buildingCabalPackage == YesBuildingCabalPackage
+                       then parens (text "Try adding" <+> quotes (ppr pi_mod_name)
+                               <+> text "to the"
+                               <+> quotes (text "signatures")
+                               <+> text "field in your Cabal file.")
+                       else parens (text "Try passing -instantiated-with=\"" <>
+                                    suggested_instantiated_with <> text "\"" $$
+                                       text "replacing <" <> ppr pi_mod_name <> text "> as necessary.")
+         in mkSimpleDecorated msg
+    DriverFileNotFound hsFilePath
+      -> mkSimpleDecorated (text "Can't find" <+> text hsFilePath)
+    DriverStaticPointersNotSupported
+      -> mkSimpleDecorated (text "StaticPointers is not supported in GHCi interactive expressions.")
+    DriverBackpackModuleNotFound modname
+      -> mkSimpleDecorated (text "module" <+> ppr modname <+> text "was not found")
+
+  diagnosticReason = \case
+    DriverUnknownMessage m
+      -> diagnosticReason m
+    DriverPsHeaderMessage {}
+      -> ErrorWithoutFlag
+    DriverMissingHomeModules{}
+      -> WarningWithFlag Opt_WarnMissingHomeModules
+    DriverUnusedPackages{}
+      -> WarningWithFlag Opt_WarnUnusedPackages
+    DriverUnnecessarySourceImports{}
+      -> WarningWithFlag Opt_WarnUnusedImports
+    DriverDuplicatedModuleDeclaration{}
+      -> ErrorWithoutFlag
+    DriverModuleNotFound{}
+      -> ErrorWithoutFlag
+    DriverFileModuleNameMismatch{}
+      -> ErrorWithoutFlag
+    DriverUnexpectedSignature{}
+      -> ErrorWithoutFlag
+    DriverFileNotFound{}
+      -> ErrorWithoutFlag
+    DriverStaticPointersNotSupported
+      -> WarningWithoutFlag
+    DriverBackpackModuleNotFound{}
+      -> ErrorWithoutFlag