[Git][ghc/ghc][master] Add -Wmissing-role-annotations
Marge Bot (@marge-bot)
gitlab at gitlab.haskell.org
Tue May 16 11:28:10 UTC 2023
Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC
Commits:
bdb93cd2 by Oleg Grenrus at 2023-05-16T07:59:21+03:00
Add -Wmissing-role-annotations
Implements #22702
- - - - -
12 changed files:
- compiler/GHC/Driver/Flags.hs
- compiler/GHC/Driver/Session.hs
- compiler/GHC/Tc/Errors/Ppr.hs
- compiler/GHC/Tc/Errors/Types.hs
- compiler/GHC/Tc/TyCl.hs
- compiler/GHC/Types/Error/Codes.hs
- docs/users_guide/using-warnings.rst
- testsuite/tests/linters/notes.stdout
- + testsuite/tests/warnings/should_compile/T22702a.hs
- + testsuite/tests/warnings/should_compile/T22702a.stderr
- + testsuite/tests/warnings/should_compile/T22702b.hs
- testsuite/tests/warnings/should_compile/all.T
Changes:
=====================================
compiler/GHC/Driver/Flags.hs
=====================================
@@ -636,6 +636,7 @@ data WarningFlag =
| Opt_WarnTypeEqualityRequiresOperators -- Since 9.4
| Opt_WarnLoopySuperclassSolve -- Since 9.6
| Opt_WarnTermVariableCapture -- Since 9.8
+ | Opt_WarnMissingRoleAnnotations -- Since 9.8
deriving (Eq, Ord, Show, Enum)
-- | Return the names of a WarningFlag
@@ -742,6 +743,7 @@ warnFlagNames wflag = case wflag of
Opt_WarnTypeEqualityOutOfScope -> "type-equality-out-of-scope" :| []
Opt_WarnLoopySuperclassSolve -> "loopy-superclass-solve" :| []
Opt_WarnTypeEqualityRequiresOperators -> "type-equality-requires-operators" :| []
+ Opt_WarnMissingRoleAnnotations -> "missing-role-annotations" :| []
-- -----------------------------------------------------------------------------
-- Standard sets of warning options
=====================================
compiler/GHC/Driver/Session.hs
=====================================
@@ -2249,7 +2249,8 @@ wWarningFlagsDeps = mconcat [
warnSpec Opt_WarnGADTMonoLocalBinds,
warnSpec Opt_WarnTypeEqualityOutOfScope,
warnSpec Opt_WarnTypeEqualityRequiresOperators,
- warnSpec Opt_WarnTermVariableCapture
+ warnSpec Opt_WarnTermVariableCapture,
+ warnSpec Opt_WarnMissingRoleAnnotations
]
warningGroupsDeps :: [(Deprecation, FlagSpec WarningGroup)]
=====================================
compiler/GHC/Tc/Errors/Ppr.hs
=====================================
@@ -1338,6 +1338,9 @@ instance Diagnostic TcRnMessage where
TcRnSectionWithoutParentheses expr -> mkSimpleDecorated $
hang (text "A section must be enclosed in parentheses")
2 (text "thus:" <+> (parens (ppr expr)))
+ TcRnMissingRoleAnnotation name roles -> mkSimpleDecorated $
+ hang (text "Missing role annotation" <> colon)
+ 2 (text "type role" <+> ppr name <+> hsep (map ppr roles))
TcRnCapturedTermName tv_name shadowed_term_names
-> mkSimpleDecorated $
@@ -2547,6 +2550,8 @@ instance Diagnostic TcRnMessage where
-> ErrorWithoutFlag
TcRnGhciMonadLookupFail {}
-> ErrorWithoutFlag
+ TcRnMissingRoleAnnotation{}
+ -> WarningWithFlag Opt_WarnMissingRoleAnnotations
diagnosticHints = \case
TcRnUnknownMessage m
@@ -3226,6 +3231,8 @@ instance Diagnostic TcRnMessage where
-> noHints
TcRnGhciMonadLookupFail {}
-> noHints
+ TcRnMissingRoleAnnotation{}
+ -> noHints
diagnosticCode :: TcRnMessage -> Maybe DiagnosticCode
diagnosticCode = constructorCode
=====================================
compiler/GHC/Tc/Errors/Types.hs
=====================================
@@ -4168,6 +4168,18 @@ data TcRnMessage where
-> Maybe [GlobalRdrElt] -- ^ lookup result
-> TcRnMessage
+ {- TcRnMissingRoleAnnotation is a warning that occurs when type declaration
+ doesn't have a role annotatiosn
+
+ Controlled by flags:
+ - Wmissing-role-annotations
+
+ Test cases:
+ T22702
+
+ -}
+ TcRnMissingRoleAnnotation :: Name -> [Role] -> TcRnMessage
+
deriving Generic
-- | Things forbidden in @type data@ declarations.
=====================================
compiler/GHC/Tc/TyCl.hs
=====================================
@@ -4976,9 +4976,13 @@ checkValidRoleAnnots role_annots tc
| isVisibleTyConBinder tvb = Just (role, binderVar tvb)
| otherwise = Nothing
- check_roles
- = whenIsJust role_annot_decl_maybe $
- \decl@(L loc (RoleAnnotDecl _ _ the_role_annots)) ->
+ check_roles = case role_annot_decl_maybe of
+ Nothing ->
+ setSrcSpan (getSrcSpan name) $
+ -- See Note [Missing role annotations warning]
+ warnIf (not (isClassTyCon tc) && not (null vis_roles)) $
+ TcRnMissingRoleAnnotation name vis_roles
+ Just (decl@(L loc (RoleAnnotDecl _ _ the_role_annots))) ->
addRoleAnnotCtxt name $
setSrcSpanA loc $ do
{ role_annots_ok <- xoptM LangExt.RoleAnnotations
@@ -5001,6 +5005,39 @@ checkValidRoleAnnots role_annots tc
check_no_roles
= whenIsJust role_annot_decl_maybe illegalRoleAnnotDecl
+-- Note [Missing role annotations warning]
+--
+-- We warn about missing role annotations for tycons
+-- 1. not type-classes:
+-- type classes are nominal by default, which is most conservative
+-- choice. E.g. we cannot have a type-class with an (accidentally)
+-- phantom or representational type variable, as we can with
+-- data types.
+-- 2. with visible roles
+--
+-- We don't make any exceptions for other data types.
+-- In particular we explicitly warn about omitted (default and common)
+-- representational roles. That is the point of the warning.
+-- For example the default representational role for `Map`s key type parameter
+-- would be wrong, and this warning is there to warn about it,
+-- asking users to be explicit.
+--
+-- If the default roles have been nominal, i.e. as conservative as possible,
+-- the warning would still be valuable, as most types can be `representational`
+-- (c.f. type-classes, which usually cannot).
+--
+-- We don't warn about types with invisible roles only, because users cannot
+-- specify them:
+--
+-- type Foo :: forall {k}. Type
+-- data Foo = Foo Int
+-- type role Foo phantom
+--
+-- is incorrect, GHC complains:
+-- Wrong number of roles listed in role annotation;
+-- Expected 0, got 1:
+--
+
checkRoleAnnot :: TyVar -> LocatedAn NoEpAnns (Maybe Role) -> Role -> TcM ()
checkRoleAnnot _ (L _ Nothing) _ = return ()
checkRoleAnnot tv (L _ (Just r1)) r2
=====================================
compiler/GHC/Types/Error/Codes.hs
=====================================
@@ -439,6 +439,7 @@ type family GhcDiagnosticCode c = n | n -> c where
GhcDiagnosticCode "TcRnUnexpectedKindVar" = 12875
GhcDiagnosticCode "TcRnNegativeNumTypeLiteral" = 93632
GhcDiagnosticCode "TcRnUnusedQuantifiedTypeVar" = 54180
+ GhcDiagnosticCode "TcRnMissingRoleAnnotation" = 65490
GhcDiagnosticCode "TcRnUntickedPromotedThing" = 49957
GhcDiagnosticCode "TcRnIllegalBuiltinSyntax" = 39716
=====================================
docs/users_guide/using-warnings.rst
=====================================
@@ -2393,6 +2393,28 @@ of ``-W(no-)*``.
When :ghc-flag:`-Wterm-variable-capture` is enabled, GHC warns against implicit quantification
that would stop working under ``RequiredTypeArguments``.
+.. ghc-flag:: -Wmissing-role-annotations
+ :shortdesc: warn when type declarations don't have role annotations
+ :type: dynamic
+ :reverse: -Wno-role-annotations-signatures
+ :category:
+
+ :since: 9.8
+ :default: off
+
+ .. index::
+ single: roles, missing
+
+ If you would like GHC to check that every data type definition
+ has a :ref:`role annotation <role-annotations>`, use the
+ :ghc-flag:`-Wmissing-role-annotations` option.
+ You can specify the role via :extension:`RoleAnnotations`.
+
+ GHC will not warn about type class definitions with missing role annotations,
+ as their default roles are the strictest: all nominal.
+ In other words the type-class role cannot be accidentally left
+ representational or phantom, which could affected the code correctness.
+
If you're feeling really paranoid, the :ghc-flag:`-dcore-lint` option is a good choice.
It turns on heavyweight intra-pass sanity-checking within GHC. (It checks GHC's
=====================================
testsuite/tests/linters/notes.stdout
=====================================
@@ -34,6 +34,8 @@ ref compiler/GHC/Tc/Instance/Family.hs:474:35: Note [Constrained family i
ref compiler/GHC/Tc/Module.hs:711:15: Note [Extra dependencies from .hs-boot files]
ref compiler/GHC/Tc/Solver/Rewrite.hs:1009:7: Note [Stability of rewriting]
ref compiler/GHC/Tc/TyCl.hs:1130:6: Note [Unification variables need fresh Names]
+ref compiler/GHC/Tc/TyCl.hs:4982:17: Note [Missing role annotations warning]
+ref compiler/GHC/Tc/TyCl.hs:5008:3: Note [Missing role annotations warning]
ref compiler/GHC/Tc/Types.hs:692:33: Note [Extra dependencies from .hs-boot files]
ref compiler/GHC/Tc/Types.hs:1423:47: Note [Care with plugin imports]
ref compiler/GHC/Tc/Types/Constraint.hs:226:34: Note [NonCanonical Semantics]
=====================================
testsuite/tests/warnings/should_compile/T22702a.hs
=====================================
@@ -0,0 +1,25 @@
+{-# OPTIONS_GHC -Wmissing-role-annotations #-}
+{-# LANGUAGE RoleAnnotations #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE StandaloneKindSignatures #-}
+module T22702a where
+
+import Data.Kind (Type)
+
+-- type with parameters
+-- warns
+type Foo :: Type -> Type -> Type
+data Foo x y = Foo x
+
+-- type without parameters
+-- doesn't warn
+data Quu = Quu1 | Quu2
+
+-- polykinded type
+-- warns, no role for `k`
+type Bar :: (k -> Type) -> k -> Type
+data Bar f a = Bar (f a)
+
+-- type-class may have roles as well
+-- doesn't warn
+class C a where
=====================================
testsuite/tests/warnings/should_compile/T22702a.stderr
=====================================
@@ -0,0 +1,6 @@
+
+T22702a.hs:12:1: warning: [GHC-65490] [-Wmissing-role-annotations]
+ Missing role annotation: type role Foo representational phantom
+
+T22702a.hs:21:1: warning: [GHC-65490] [-Wmissing-role-annotations]
+ Missing role annotation: type role Bar representational nominal
=====================================
testsuite/tests/warnings/should_compile/T22702b.hs
=====================================
@@ -0,0 +1,23 @@
+{-# OPTIONS_GHC -Wmissing-role-annotations #-}
+{-# LANGUAGE RoleAnnotations #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE StandaloneKindSignatures #-}
+module T22702b where
+
+import Data.Kind (Type)
+
+-- type with parameters
+type Foo :: Type -> Type -> Type
+type role Foo representational phantom
+data Foo x y = Foo x
+
+-- type without parameters
+data Quu = Quu1 | Quu2
+
+-- polykinded type
+type Bar :: (k -> Type) -> k -> Type
+type role Bar representational nominal
+data Bar f a = Bar (f a)
+
+-- type-class may have roles as well
+class C a where
=====================================
testsuite/tests/warnings/should_compile/all.T
=====================================
@@ -62,3 +62,5 @@ test('T22759', normal, compile, [''])
test('T22676', [extra_files(['src'])], multimod_compile, ['src.hs', '-working-dir src -Wmissing-home-modules -v0'])
test('DodgyImports', normal, compile, ['-Wdodgy-imports'])
test('DodgyImports_hiding', normal, compile, ['-Wdodgy-imports'])
+test('T22702a', normal, compile, [''])
+test('T22702b', normal, compile, [''])
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/bdb93cd28f4a40e9a9f28b0976ca8fa4f250cad2
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/bdb93cd28f4a40e9a9f28b0976ca8fa4f250cad2
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