[Git][ghc/ghc][master] Add a hint to enable ExplicitNamespaces for type operator imports (Fixes/Enhances #20007)

[Marge Bot (@marge-bot)]

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
8e11630e by jade at 2023-07-10T16:58:40-04:00
Add a hint to enable ExplicitNamespaces for type operator imports (Fixes/Enhances #20007)

As suggested in #20007 and implemented in !8895, trying to import type operators
will suggest a fix to use the 'type' keyword, without considering whether
ExplicitNamespaces is enabled. This patch will query whether ExplicitNamespaces
is enabled and add a hint to suggest enabling ExplicitNamespaces if it isn't enabled,
alongside the suggestion of adding the 'type' keyword.

- - - - -


7 changed files:

- compiler/GHC/Rename/Names.hs
- compiler/GHC/Tc/Errors/Ppr.hs
- compiler/GHC/Tc/Errors/Types.hs
- compiler/GHC/Types/Hint/Ppr.hs
- + testsuite/tests/module/T20007.hs
- + testsuite/tests/module/T20007.stderr
- testsuite/tests/module/all.T


Changes:

=====================================
compiler/GHC/Rename/Names.hs
=====================================
@@ -2139,11 +2139,12 @@ badImportItemErr
   -> TcRn ImportLookupReason
 badImportItemErr iface decl_spec ie sub avails = do
   patsyns_enabled <- xoptM LangExt.PatternSynonyms
-  pure (ImportLookupBad importErrorKind iface decl_spec ie patsyns_enabled)
+  expl_ns_enabled <- xoptM LangExt.ExplicitNamespaces
+  pure (ImportLookupBad (importErrorKind expl_ns_enabled) iface decl_spec ie patsyns_enabled)
   where
-    importErrorKind
+    importErrorKind expl_ns_enabled
       | any checkIfTyCon avails = case sub of
-          BadImportIsParent -> BadImportAvailTyCon
+          BadImportIsParent -> BadImportAvailTyCon expl_ns_enabled
           BadImportIsSubordinate -> BadImportNotExportedSubordinates unavailableChildren
       | any checkIfVarName avails = BadImportAvailVar
       | Just con <- find checkIfDataCon avails = BadImportAvailDataCon (availOccName con)


=====================================
compiler/GHC/Tc/Errors/Ppr.hs
=====================================
@@ -3108,7 +3108,9 @@ instance Diagnostic TcRnMessage where
       in case k of
         BadImportAvailVar         -> [ImportSuggestion occ $ CouldRemoveTypeKeyword mod_name]
         BadImportNotExported      -> noHints
-        BadImportAvailTyCon       -> [ImportSuggestion occ $ CouldAddTypeKeyword mod_name]
+        BadImportAvailTyCon ex_ns ->
+          [useExtensionInOrderTo empty LangExt.ExplicitNamespaces | not ex_ns]
+          ++ [ImportSuggestion occ $ CouldAddTypeKeyword mod_name]
         BadImportAvailDataCon par -> [ImportSuggestion occ $ ImportDataCon (Just (mod_name, patsyns_enabled)) par]
         BadImportNotExportedSubordinates{} -> noHints
     TcRnImportLookup{}


=====================================
compiler/GHC/Tc/Errors/Types.hs
=====================================
@@ -5263,7 +5263,9 @@ data BadImportKind
   -- | Module does not export...
   = BadImportNotExported
   -- | Missing @type@ keyword when importing a type.
-  | BadImportAvailTyCon
+  -- e.g.  `import TypeLits( (+) )`, where TypeLits exports a /type/ (+), not a /term/ (+)
+  -- Then we want to suggest using `import TypeLits( type (+) )`
+  | BadImportAvailTyCon Bool -- ^ is ExplicitNamespaces enabled?
   -- | Trying to import a data constructor directly, e.g.
   -- @import Data.Maybe (Just)@ instead of @import Data.Maybe (Maybe(Just))@
   | BadImportAvailDataCon OccName


=====================================
compiler/GHC/Types/Hint/Ppr.hs
=====================================
@@ -310,12 +310,12 @@ pprImportSuggestion occ_name (CouldUnhideFrom mods)
         | (mod,imv) <- NE.toList mods
         ])
 pprImportSuggestion occ_name (CouldAddTypeKeyword mod)
- = vcat [ text "Add the" <+> quotes (text "type")
+  = vcat [ text "Add the" <+> quotes (text "type")
           <+> text "keyword to the import statement:"
-        , nest 2 $ text "import"
+         , nest 2 $ text "import"
             <+> ppr mod
             <+> parens_sp (text "type" <+> pprPrefixOcc occ_name)
-        ]
+         ]
   where
     parens_sp d = parens (space <> d <> space)
 pprImportSuggestion occ_name (CouldRemoveTypeKeyword mod)


=====================================
testsuite/tests/module/T20007.hs
=====================================
@@ -0,0 +1 @@
+import Data.Type.Equality ( (~) )


=====================================
testsuite/tests/module/T20007.stderr
=====================================
@@ -0,0 +1,8 @@
+
+T20007.hs:1:29: [GHC-56449]
+    In the import of ‘Data.Type.Equality’:
+      an item called ‘(~)’ is exported, but it is a type.
+    Suggested fixes:
+       Use ExplicitNamespaces
+       Add the ‘type’ keyword to the import statement:
+          import Data.Type.Equality ( type (~) )


=====================================
testsuite/tests/module/all.T
=====================================
@@ -298,3 +298,4 @@ test('T21752', [extra_files(['T21752A.hs', 'T21752.hs'])], multimod_compile, ['T
 
 test('TupleTyConUserSyntax', [extra_files(['TupleTyConUserSyntaxA.hs', 'TupleTyConUserSyntax.hs'])], multimod_compile, ['TupleTyConUserSyntax', '-v0'])
 test('T21826', normal, compile_fail, [''])
+test('T20007', normal, compile_fail, [''])



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/8e11630ec9669414b0b37a3097fb509d60702b0a

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/8e11630ec9669414b0b37a3097fb509d60702b0a
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