[Git][ghc/ghc][wip/sand-witch/modern-STV-extension-shuffling] Extension shuffling (#23291)
Andrei Borzenkov (@sand-witch)
gitlab at gitlab.haskell.org
Wed Jun 7 07:23:02 UTC 2023
Andrei Borzenkov pushed to branch wip/sand-witch/modern-STV-extension-shuffling at Glasgow Haskell Compiler / GHC
Commits:
83a32273 by Andrei Borzenkov at 2023-06-07T11:22:35+04:00
Extension shuffling (#23291)
Where introduced 3 new extensions:
- PatternSignatures
- ExtendedForAllScope
- MethodTypeVariables
Tasks of ScopedTypeVariables extension were distributed between
PatternSignatures, ExtendedForAllScope and MethodTypeVariables according
to the proposal. Now ScopedTypeVaribles only implies these three exntesions.
- - - - -
29 changed files:
- compiler/GHC/Driver/DynFlags.hs
- compiler/GHC/Driver/Session.hs
- compiler/GHC/Hs/Type.hs
- compiler/GHC/Rename/Bind.hs
- compiler/GHC/Rename/HsType.hs
- compiler/GHC/Rename/Module.hs
- compiler/GHC/Tc/Deriv.hs
- compiler/GHC/Tc/Deriv/Generate.hs
- compiler/GHC/Tc/Errors/Ppr.hs
- compiler/GHC/Tc/Errors/Types.hs
- docs/users_guide/9.8.1-notes.rst
- docs/users_guide/expected-undocumented-flags.txt
- docs/users_guide/exts/explicit_forall.rst
- docs/users_guide/exts/gadt.rst
- docs/users_guide/exts/scoped_type_variables.rst
- docs/users_guide/exts/type_abstractions.rst
- libraries/ghc-boot-th/GHC/LanguageExtensions/Type.hs
- testsuite/tests/driver/T4437.hs
- testsuite/tests/rename/should_fail/T11663.stderr
- testsuite/tests/showIface/DocsInHiFile1.stdout
- testsuite/tests/showIface/DocsInHiFileTH.stdout
- testsuite/tests/showIface/HaddockIssue849.stdout
- testsuite/tests/showIface/HaddockOpts.stdout
- testsuite/tests/showIface/LanguageExts.stdout
- testsuite/tests/showIface/MagicHashInHaddocks.stdout
- testsuite/tests/showIface/NoExportList.stdout
- testsuite/tests/showIface/PragmaDocs.stdout
- testsuite/tests/showIface/ReExports.stdout
- testsuite/tests/typecheck/should_fail/PatSynExistential.stderr
Changes:
=====================================
compiler/GHC/Driver/DynFlags.hs
=====================================
@@ -1417,7 +1417,13 @@ languageExtensions (Just GHC2021)
LangExt.PostfixOperators,
LangExt.RankNTypes,
LangExt.ScopedTypeVariables,
- LangExt.TypeAbstractions, -- implied by ScopedTypeVariables according to GHC Proposal #448 "Modern Scoped Type Variables"
+
+ -- implied by ScopedTypeVariables according to GHC Proposal #448 "Modern Scoped Type Variables"
+ LangExt.TypeAbstractions,
+ LangExt.PatternSignatures,
+ LangExt.MethodTypeVariables,
+ LangExt.ExtendedForAllScope,
+
LangExt.StandaloneDeriving,
LangExt.StandaloneKindSignatures,
LangExt.TupleSections,
=====================================
compiler/GHC/Driver/Session.hs
=====================================
@@ -2673,8 +2673,9 @@ xFlagsDeps = [
flagSpec "ParallelListComp" LangExt.ParallelListComp,
flagSpec "PartialTypeSignatures" LangExt.PartialTypeSignatures,
flagSpec "PatternGuards" LangExt.PatternGuards,
- depFlagSpec' "PatternSignatures" LangExt.ScopedTypeVariables
- (deprecatedForExtension "ScopedTypeVariables"),
+ flagSpec "PatternSignatures" LangExt.PatternSignatures,
+ flagSpec "MethodTypeVariables" LangExt.MethodTypeVariables,
+ flagSpec "ExtendedForAllScope" LangExt.ExtendedForAllScope,
flagSpec "PatternSynonyms" LangExt.PatternSynonyms,
flagSpec "PolyKinds" LangExt.PolyKinds,
flagSpec "PolymorphicComponents" LangExt.RankNTypes,
@@ -2767,6 +2768,9 @@ impliedXFlags
-- In accordance with GHC Proposal #448 "Modern Scoped Type Variables"
, (LangExt.ScopedTypeVariables, turnOn, LangExt.TypeAbstractions)
+ , (LangExt.ScopedTypeVariables, turnOn, LangExt.PatternSignatures)
+ , (LangExt.ScopedTypeVariables, turnOn, LangExt.MethodTypeVariables)
+ , (LangExt.ScopedTypeVariables, turnOn, LangExt.ExtendedForAllScope)
, (LangExt.RebindableSyntax, turnOff, LangExt.ImplicitPrelude) -- NB: turn off!
=====================================
compiler/GHC/Hs/Type.hs
=====================================
@@ -819,9 +819,9 @@ enabled. For example, the following will be rejected:
instance (Eq a => Show (Maybe a)) where ...
This restriction is partly motivated by an unusual quirk of instance
-declarations. Namely, if ScopedTypeVariables is enabled, then the type
-variables from the top of an instance will scope over the bodies of the
-instance methods, /even if the type variables are implicitly quantified/.
+declarations. Namely, if MethodTypeVariables (implied by ScopedTypeVariables) is enabled,
+then the type variables from the top of an instance will scope over the bodies
+of the instance methods, /even if the type variables are implicitly quantified/.
For example, GHC will accept the following:
instance Monoid a => Monoid (Identity a) where
@@ -841,20 +841,20 @@ Somewhat surprisingly, old versions of GHC would accept the instance above.
Even though the `forall` only quantifies `a`, the outermost parentheses mean
that the `forall` is nested, and per the forall-or-nothing rule, this means
that implicit quantification would occur. Therefore, the `a` is explicitly
-bound and the `b` is implicitly bound. Moreover, ScopedTypeVariables would
-bring /both/ sorts of type variables into scope over the body of `m`.
+bound and the `b` is implicitly bound. Moreover, MethodTypeVariables
+would bring /both/ sorts of type variables into scope over the body of `m`.
How utterly confusing!
To avoid this sort of confusion, we simply disallow nested `forall`s in
instance types, which makes things like the instance above become illegal.
For the sake of consistency, we also disallow nested contexts, even though they
-don't have the same strange interaction with ScopedTypeVariables.
+don't have the same strange interaction with MethodTypeVariables.
Just as we forbid nested `forall`s and contexts in normal instance
declarations, we also forbid them in SPECIALISE instance pragmas (#18455).
-Unlike normal instance declarations, ScopedTypeVariables don't have any impact
-on SPECIALISE instance pragmas, but we use the same validity checks for
-SPECIALISE instance pragmas anyway to be consistent.
+Unlike normal instance declarations, MethodTypeVariables
+don't have any impact on SPECIALISE instance pragmas, but we use the same
+validity checks for SPECIALISE instance pragmas anyway to be consistent.
-----
-- Wrinkle: Derived instances
@@ -863,7 +863,7 @@ SPECIALISE instance pragmas anyway to be consistent.
`deriving` clauses and standalone `deriving` declarations also permit bringing
type variables into scope, either through explicit or implicit quantification.
Unlike in the tops of instance declarations, however, one does not need to
-enable ScopedTypeVariables for this to take effect.
+enable MethodTypeVariables for this to take effect.
Just as GHC forbids nested `forall`s in the top of instance declarations, it
also forbids them in types involved with `deriving`:
=====================================
compiler/GHC/Rename/Bind.hs
=====================================
@@ -920,7 +920,8 @@ rnMethodBinds is_cls_decl cls ktv_names binds sigs
-- Rename the bindings RHSs. Again there's an issue about whether the
-- type variables from the class/instance head are in scope.
-- Answer no in Haskell 2010, but yes if you have -XScopedTypeVariables
- ; (binds'', bind_fvs) <- bindSigTyVarsFV ktv_names $
+ -- or -XMethodTypeVariables
+ ; (binds'', bind_fvs) <- bindClassInstanceHeadTyVarsFV ktv_names $
do { binds_w_dus <- mapBagM (rnLBind (mkScopedTvFn other_sigs')) binds'
; let bind_fvs = foldr (\(_,_,fv1) fv2 -> fv1 `plusFV` fv2)
emptyFVs binds_w_dus
=====================================
compiler/GHC/Rename/HsType.hs
=====================================
@@ -31,7 +31,8 @@ module GHC.Rename.HsType (
-- Binding related stuff
bindHsOuterTyVarBndrs, bindHsForAllTelescope,
bindLHsTyVarBndr, bindLHsTyVarBndrs, WarnUnusedForalls(..),
- rnImplicitTvOccs, bindSigTyVarsFV, bindHsQTyVars,
+ rnImplicitTvOccs, bindSigTyVarsFV, bindClassInstanceHeadTyVarsFV ,
+ bindHsQTyVars,
FreeKiTyVars, filterInScopeM,
extractHsTyRdrTyVars, extractHsTyRdrTyVarsKindVars,
extractHsTysRdrTyVars, extractRdrKindSigVars,
@@ -150,20 +151,27 @@ rnHsPatSigType :: HsPatSigTypeScoping
-> (HsPatSigType GhcRn -> RnM (a, FreeVars))
-> RnM (a, FreeVars)
-- Used for
--- - Pattern type signatures, which are only allowed with ScopedTypeVariables
+-- - Pattern type signatures, which are only allowed with PatternSignatures
-- - Signatures on binders in a RULE, which are allowed even if
--- ScopedTypeVariables isn't enabled
+-- PatternSignatures isn't enabled
-- Wildcards are allowed
--
-- See Note [Pattern signature binders and scoping] in GHC.Hs.Type
rnHsPatSigType scoping ctx sig_ty thing_inside
- = do { ty_sig_okay <- xoptM LangExt.ScopedTypeVariables
+ = do { ty_sig_okay <- xoptM LangExt.PatternSignatures
+ ; free_var_should_bind <- xoptM LangExt.ExtendedForAllScope
; checkErr ty_sig_okay (unexpectedPatSigTypeErr sig_ty)
; free_vars <- filterInScopeM (extractHsTyRdrTyVars pat_sig_ty)
; (nwc_rdrs', tv_rdrs) <- partition_nwcs free_vars
; let nwc_rdrs = nubN nwc_rdrs'
implicit_bndrs = case scoping of
- AlwaysBind -> tv_rdrs
+ AlwaysBind ->
+ -- `PatternSignatures` doesn't enable binding of
+ -- free type variables in pattern signatures.
+ -- That does `ExtendedForAllScope`.
+ if free_var_should_bind
+ then tv_rdrs
+ else []
NeverBind -> []
; rnImplicitTvOccs Nothing implicit_bndrs $ \ imp_tvs ->
do { (nwcs, pat_sig_ty', fvs1) <- rnWcBody ctx nwc_rdrs pat_sig_ty
@@ -900,18 +908,25 @@ notInKinds _ _ = return ()
* *
***************************************************** -}
-bindSigTyVarsFV :: [Name]
- -> RnM (a, FreeVars)
- -> RnM (a, FreeVars)
-- Used just before renaming the defn of a function
-- with a separate type signature, to bring its tyvars into scope
--- With no -XScopedTypeVariables, this is a no-op
+-- With no -XExtendedForAllScope/-XMethodTypeVariables, this is a no-op
+bindSigTyVarsFV, bindClassInstanceHeadTyVarsFV :: [Name]
+ -> RnM (a, FreeVars)
+ -> RnM (a, FreeVars)
+
bindSigTyVarsFV tvs thing_inside
- = do { scoped_tyvars <- xoptM LangExt.ScopedTypeVariables
- ; if not scoped_tyvars then
- thing_inside
- else
- bindLocalNamesFV tvs thing_inside }
+ = do { extended_for_all_scope <- xoptM LangExt.ExtendedForAllScope
+ ; if extended_for_all_scope
+ then bindLocalNamesFV tvs thing_inside
+ else thing_inside }
+
+bindClassInstanceHeadTyVarsFV tvs thing_inside
+ = do { method_type_variables <- xoptM LangExt.MethodTypeVariables
+ ; if method_type_variables
+ then bindLocalNamesFV tvs thing_inside
+ else thing_inside }
+
---------------
bindHsQTyVars :: forall a b.
=====================================
compiler/GHC/Rename/Module.hs
=====================================
@@ -198,7 +198,7 @@ rnSrcDecls group@(HsGroup { hs_valds = val_decls,
-- (H) Rename Everything else
- (rn_rule_decls, src_fvs2) <- setXOptM LangExt.ScopedTypeVariables $
+ (rn_rule_decls, src_fvs2) <- setXOptM LangExt.PatternSignatures $
rnList rnHsRuleDecls rule_decls ;
-- Inside RULES, scoped type variables are on
(rn_foreign_decls, src_fvs3) <- rnList rnHsForeignDecl foreign_decls ;
=====================================
compiler/GHC/Tc/Deriv.hs
=====================================
@@ -273,7 +273,9 @@ renameDeriv inst_infos bagBinds
setXOptM LangExt.EmptyCase $
-- Derived decls (for empty types) can have
-- case x of {}
- setXOptM LangExt.ScopedTypeVariables $
+ setXOptM LangExt.MethodTypeVariables $
+ setXOptM LangExt.PatternSignatures $
+ setXOptM LangExt.ExtendedForAllScope $
setXOptM LangExt.KindSignatures $
-- Derived decls (for newtype-deriving) can use ScopedTypeVariables &
-- KindSignatures
=====================================
compiler/GHC/Tc/Deriv/Generate.hs
=====================================
@@ -1875,9 +1875,9 @@ of the method. For example, recall:
join
In the example above, it is imperative that the `a` in the instance signature
-for `join` scope over the body of `join` by way of ScopedTypeVariables.
-This might sound obvious, but note that in gen_Newtype_binds, which is
-responsible for generating the code above, the type in `join`'s instance
+for `join` scope over the body of `join` by way of ExtendedForallScope (implied
+by ScopedTypeVariables). This might sound obvious, but note that in gen_Newtype_binds,
+which is responsible for generating the code above, the type in `join`'s instance
signature is given as a Core type, whereas gen_Newtype_binds will eventually
produce HsBinds (i.e., source Haskell) that is renamed and typechecked. We
must ensure that `a` is in scope over the body of `join` during renaming
=====================================
compiler/GHC/Tc/Errors/Ppr.hs
=====================================
@@ -1637,9 +1637,7 @@ instance Diagnostic TcRnMessage where
nest 4 (text "in the section:" <+> quotes (ppr section))]
TcRnUnexpectedPatSigType ty
- -> mkSimpleDecorated $
- hang (text "Illegal type signature:" <+> quotes (ppr ty))
- 2 (text "Type signatures are only allowed in patterns with ScopedTypeVariables")
+ -> mkSimpleDecorated $ text "Illegal type signature:" <+> quotes (ppr ty)
TcRnIllegalKindSignature ty
-> mkSimpleDecorated $ text "Illegal kind signature:" <+> quotes (ppr ty)
@@ -3011,7 +3009,7 @@ instance Diagnostic TcRnMessage where
TcRnSectionPrecedenceError{}
-> noHints
TcRnUnexpectedPatSigType{}
- -> [suggestExtension LangExt.ScopedTypeVariables]
+ -> [suggestExtension LangExt.PatternSignatures]
TcRnIllegalKindSignature{}
-> [suggestExtension LangExt.KindSignatures]
TcRnUnusedQuantifiedTypeVar{}
=====================================
compiler/GHC/Tc/Errors/Types.hs
=====================================
@@ -2381,7 +2381,7 @@ data TcRnMessage where
-> TcRnMessage
{-| TcRnUnexpectedPatSigType is an error occurring when there is
- a type signature in a pattern without -XScopedTypeVariables extension
+ a type signature in a pattern without -XPatternSignatures extension
Examples:
f (a :: Bool) = ...
=====================================
docs/users_guide/9.8.1-notes.rst
=====================================
@@ -10,6 +10,11 @@ Language
sized primitive literals, e.g. ``123#Int8`` is a literal of type ``Int8#``.
See the GHC proposal `#451 <https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0451-sized-literals.rst>`_.
+- :extension:`ScopedTypeVariables` was split into several new extensions:
+ :extension:`PatternSignatures`, :extension:`ExtendedForAllScope`, :extension:`MethodTypeVariables`.
+ You can set :extension:`ScopedTypeVariables` to enable them all or enable them individually
+ for more fine-grained control of features that you want to have.
+
Compiler
~~~~~~~~
=====================================
docs/users_guide/expected-undocumented-flags.txt
=====================================
@@ -14,7 +14,6 @@
-XMonomorphismRestriction
-XParallelArrays
-XPatternGuards
--XPatternSignatures
-XPolymorphicComponents
-XRecordPuns
-XRelaxedLayout
=====================================
docs/users_guide/exts/explicit_forall.rst
=====================================
@@ -114,7 +114,7 @@ The ``forall``-or-nothing rule takes effect in the following places:
Notes:
-- :ref:`pattern-type-sigs` are a notable example of a place where
+- :extension:`PatternSignatures` are a notable example of a place where
types do *not* obey the ``forall``-or-nothing rule. For example, GHC will
accept the following: ::
=====================================
docs/users_guide/exts/gadt.rst
=====================================
@@ -194,7 +194,7 @@ also sets :extension:`GADTSyntax` and :extension:`MonoLocalBinds`.
In the function clause for ``g``, GHC first checks ``MkF``, the outermost
pattern, followed by the inner ``Nothing`` pattern. This outside-in order
- can interact somewhat counterintuitively with :ref:`pattern-type-sigs`.
+ can interact somewhat counterintuitively with :extension:`PatternSignatures`.
Consider the following variation of ``g``: ::
g2 :: F a a -> a
=====================================
docs/users_guide/exts/scoped_type_variables.rst
=====================================
@@ -6,9 +6,13 @@ Lexically scoped type variables
===============================
.. extension:: ScopedTypeVariables
- :shortdesc: Enable lexically-scoped type variables.
+ :shortdesc: Enable lexically-scoped type variables everywhere.
- :implies: :extension:`ExplicitForAll`
+ :implies: :extension:`ExplicitForAll`,
+ :extension:`PatternSignatures`,
+ :extension:`ExtendedForAllScope`,
+ :extension:`MethodTypeVariables`,
+ :extension:`TypeAbstractions`
:since: 6.8.1
@@ -26,7 +30,7 @@ Lexically scoped type variables
To trigger those forms of :extension:`ScopedTypeVariables`, the ``forall`` must appear against the top-level signature (or outer expression)
but *not* against nested signatures referring to the same type variables.
- Explicit ``forall`` is not always required -- see :ref:`pattern signature equivalent <pattern-equiv-form>` for the example in this section, or :ref:`pattern-type-sigs`.
+ Explicit ``forall`` is not always required -- see :ref:`pattern signature equivalent <pattern-equiv-form>` for the example in this section, or :extension:`PatternSignatures`.
GHC supports *lexically scoped type variables*, without which some type
signatures are simply impossible to write. For example: ::
@@ -48,7 +52,7 @@ possible to do so.
.. _pattern-equiv-form:
-An equivalent form for that example, avoiding explicit ``forall`` uses :ref:`pattern-type-sigs`: ::
+An equivalent form for that example, avoiding explicit ``forall`` uses :extension:`PatternSignatures`: ::
f :: [a] -> [a]
f (xs :: [aa]) = xs ++ ys
@@ -84,9 +88,9 @@ A *lexically scoped type variable* can be bound by:
- An expression type signature (:ref:`exp-type-sigs`)
-- A pattern type signature (:ref:`pattern-type-sigs`)
+- A pattern type signature (:extension:`PatternSignatures`)
-- Class and instance declarations (:ref:`cls-inst-scoped-tyvars`)
+- Class and instance declarations (:extension:`MethodTypeVariables`)
In Haskell, a programmer-written type signature is implicitly quantified
over its free type variables (`Section
@@ -100,14 +104,31 @@ scope is *not* universally quantified. For example, if type variable
(e :: b -> b) means (e :: forall b. b->b)
(e :: a -> b) means (e :: forall b. a->b)
+Extended ForAll Scope
+=====================
+
+.. extension:: ExtendedForAllScope
+ :shortdesc: Enable lexically-scoped type variables in function bindings,
+ pattern synonyms and expression type signatures.
+
+ :since: 9.8.1
+
+ :implied by: :extension:`ScopedTypeVariables`
+
+ :status: Included in :extension:`GHC2021`
+
+ Enable lexical scoping of type variables explicitly introduced with
+ a ``forall`` in function bindings, pattern synonyms and expression type signatures.
+
.. _decl-type-sigs:
Declaration type signatures
---------------------------
-A declaration type signature that has *explicit* quantification (using
-``forall``) brings into scope the explicitly-quantified type variables,
-in the definition of the named function. For example: ::
+When :extension:`ExtendedForAllScope` is enabled, a declaration type signature
+that has *explicit* quantification (using ``forall``) brings into scope the
+explicitly-quantified type variables, in the definition of the named function.
+For example: ::
f :: forall a. [a] -> [a]
f (x:xs) = xs ++ [ x :: a ]
@@ -171,9 +192,9 @@ This only happens if:
Expression type signatures
--------------------------
-An expression type signature that has *explicit* quantification (using
-``forall``) brings into scope the explicitly-quantified type variables,
-in the annotated expression. For example: ::
+When :extension:`ExtendedForAllScope` is enabled, an expression type signature
+that has *explicit* quantification (using ``forall``) brings into scope the
+explicitly-quantified type variables, in the annotated expression. For example: ::
f = runST ( (op >>= \(x :: STRef s Int) -> g x) :: forall s. ST s Bool )
@@ -181,13 +202,22 @@ Here, the type signature ``forall s. ST s Bool`` brings the type
variable ``s`` into scope, in the annotated expression
``(op >>= \(x :: STRef s Int) -> g x)``.
-.. _pattern-type-sigs:
+Pattern Signatures
+==================
+
+.. extension:: PatternSignatures
+ :shortdesc: Allow type signatures in patterns.
-Pattern type signatures
------------------------
+ :since: 9.8.1
-A type signature may occur in any pattern; this is a *pattern type
-signature*. For example: ::
+ :implied by: :extension:`ScopedTypeVariables`
+
+ :status: Included in :extension:`GHC2021`
+
+ Allow type signatures and type variable bindings in patterns.
+
+When :extension:`PatternSignatures` is enabled, a type signature may occur
+in any pattern; this is a *pattern type signature*. For example: ::
-- f and g assume that 'a' is already in scope
f = \(x::Int, y::a) -> x
@@ -259,12 +289,21 @@ they are both legal whether or not ``a`` is already in scope.
They differ in that *if* ``a`` is already in scope, the signature constrains
the pattern, rather than the pattern binding the variable.
-.. _cls-inst-scoped-tyvars:
+Method Type Variables
+=====================
+
+.. extension:: MethodTypeVariables
+ :shortdesc: Enable lexically-scoped type variables in class and instance declarations.
+
+ :since: 9.8.1
+
+ :implied by: :extension:`ScopedTypeVariables`
+
+ :status: Included in :extension:`GHC2021`
-Class and instance declarations
--------------------------------
+ Enable lexical scoping of type variables explicitly introduced by class and instance heads.
-:extension:`ScopedTypeVariables` allow the type variables bound by the top of a
+:extension:`MethodTypeVariables` allow the type variables bound by the top of a
``class`` or ``instance`` declaration to scope over the methods defined in the
``where`` part. Unlike :ref:`decl-type-sigs`, type variables from class and
instance declarations can be lexically scoped without an explicit ``forall``
@@ -286,11 +325,11 @@ declaration; see :ref:`explicit-foralls`). For example: ::
instance forall b. C b => C [b] where
op xs = reverse (head (xs :: [[b]]))
-While :extension:`ScopedTypeVariables` is required for type variables from the
+While :extension:`MethodTypeVariables` is required for type variables from the
top of a class or instance declaration to scope over the /bodies/ of the
methods, it is not required for the type variables to scope over the /type
signatures/ of the methods. For example, the following will be accepted without
-explicitly enabling :extension:`ScopedTypeVariables`: ::
+explicitly enabling :extension:`MethodTypeVariables`: ::
class D a where
m :: [a] -> a
@@ -302,11 +341,11 @@ explicitly enabling :extension:`ScopedTypeVariables`: ::
Note that writing ``m :: [a] -> [a]`` requires the use of the
:extension:`InstanceSigs` extension.
-Similarly, :extension:`ScopedTypeVariables` is not required for type variables
+Similarly, :extension:`MethodTypeVariables` is not required for type variables
from the top of the class or instance declaration to scope over associated type
families, which only requires the :extension:`TypeFamilies` extension. For
instance, the following will be accepted without explicitly enabling
-:extension:`ScopedTypeVariables`: ::
+:extension:`MethodTypeVariables`: ::
class E a where
type T a
=====================================
docs/users_guide/exts/type_abstractions.rst
=====================================
@@ -6,6 +6,8 @@ Type abstractions
:since: 9.8.1
+ :implied by: :extension:`ScopedTypeVariables`
+
:status: Partially implemented
Allow the use of type abstraction syntax.
=====================================
libraries/ghc-boot-th/GHC/LanguageExtensions/Type.hs
=====================================
@@ -153,6 +153,9 @@ data Extension
| OverloadedRecordUpdate
| TypeAbstractions
| ExtendedLiterals
+ | PatternSignatures
+ | ExtendedForAllScope
+ | MethodTypeVariables
deriving (Eq, Enum, Show, Generic, Bounded)
-- 'Ord' and 'Bounded' are provided for GHC API users (see discussions
-- in https://gitlab.haskell.org/ghc/ghc/merge_requests/2707 and
=====================================
testsuite/tests/driver/T4437.hs
=====================================
@@ -38,7 +38,9 @@ check title expected got
expectedGhcOnlyExtensions :: [String]
expectedGhcOnlyExtensions =
[ "TypeAbstractions",
- "ExtendedLiterals"
+ "ExtendedLiterals",
+ "MethodTypeVariables",
+ "ExtendedForAllScope"
]
expectedCabalOnlyExtensions :: [String]
=====================================
testsuite/tests/rename/should_fail/T11663.stderr
=====================================
@@ -1,20 +1,16 @@
T11663.hs:6:12: error: [GHC-74097]
Illegal type signature: ‘Int’
- Type signatures are only allowed in patterns with ScopedTypeVariables
- Suggested fix: Perhaps you intended to use ScopedTypeVariables
+ Suggested fix: Perhaps you intended to use PatternSignatures
T11663.hs:7:9: error: [GHC-74097]
Illegal type signature: ‘Int’
- Type signatures are only allowed in patterns with ScopedTypeVariables
- Suggested fix: Perhaps you intended to use ScopedTypeVariables
+ Suggested fix: Perhaps you intended to use PatternSignatures
T11663.hs:8:22: error: [GHC-74097]
Illegal type signature: ‘Int’
- Type signatures are only allowed in patterns with ScopedTypeVariables
- Suggested fix: Perhaps you intended to use ScopedTypeVariables
+ Suggested fix: Perhaps you intended to use PatternSignatures
T11663.hs:9:32: error: [GHC-74097]
Illegal type signature: ‘Int’
- Type signatures are only allowed in patterns with ScopedTypeVariables
- Suggested fix: Perhaps you intended to use ScopedTypeVariables
+ Suggested fix: Perhaps you intended to use PatternSignatures
=====================================
testsuite/tests/showIface/DocsInHiFile1.stdout
=====================================
@@ -144,5 +144,7 @@ docs:
StandaloneKindSignatures
FieldSelectors
TypeAbstractions
+ PatternSignatures
+ ExtendedForAllScope
+ MethodTypeVariables
extensible fields:
-
=====================================
testsuite/tests/showIface/DocsInHiFileTH.stdout
=====================================
@@ -287,5 +287,7 @@ docs:
StandaloneKindSignatures
FieldSelectors
TypeAbstractions
+ PatternSignatures
+ ExtendedForAllScope
+ MethodTypeVariables
extensible fields:
-
=====================================
testsuite/tests/showIface/HaddockIssue849.stdout
=====================================
@@ -67,5 +67,7 @@ docs:
StandaloneKindSignatures
FieldSelectors
TypeAbstractions
+ PatternSignatures
+ ExtendedForAllScope
+ MethodTypeVariables
extensible fields:
-
=====================================
testsuite/tests/showIface/HaddockOpts.stdout
=====================================
@@ -59,5 +59,7 @@ docs:
StandaloneKindSignatures
FieldSelectors
TypeAbstractions
+ PatternSignatures
+ ExtendedForAllScope
+ MethodTypeVariables
extensible fields:
-
=====================================
testsuite/tests/showIface/LanguageExts.stdout
=====================================
@@ -23,4 +23,3 @@ docs:
CUSKs
FieldSelectors
extensible fields:
-
=====================================
testsuite/tests/showIface/MagicHashInHaddocks.stdout
=====================================
@@ -69,5 +69,7 @@ docs:
StandaloneKindSignatures
FieldSelectors
TypeAbstractions
+ PatternSignatures
+ ExtendedForAllScope
+ MethodTypeVariables
extensible fields:
-
=====================================
testsuite/tests/showIface/NoExportList.stdout
=====================================
@@ -95,5 +95,7 @@ docs:
StandaloneKindSignatures
FieldSelectors
TypeAbstractions
+ PatternSignatures
+ ExtendedForAllScope
+ MethodTypeVariables
extensible fields:
-
=====================================
testsuite/tests/showIface/PragmaDocs.stdout
=====================================
@@ -69,5 +69,7 @@ docs:
StandaloneKindSignatures
FieldSelectors
TypeAbstractions
+ PatternSignatures
+ ExtendedForAllScope
+ MethodTypeVariables
extensible fields:
-
=====================================
testsuite/tests/showIface/ReExports.stdout
=====================================
@@ -66,5 +66,7 @@ docs:
StandaloneKindSignatures
FieldSelectors
TypeAbstractions
+ PatternSignatures
+ ExtendedForAllScope
+ MethodTypeVariables
extensible fields:
-
=====================================
testsuite/tests/typecheck/should_fail/PatSynExistential.stderr
=====================================
@@ -1,4 +1,5 @@
-PatSynExistential.hs:6:1: [GHC-33973]
- The result type of the signature for ‘P’, namely ‘x -> Maybe x’
+
+PatSynExistential.hs:6:1: error: [GHC-33973]
+ • The result type of the signature for ‘P’, namely ‘x -> Maybe x’
mentions existential type variable ‘x’
- In the declaration for pattern synonym ‘P’
+ • In the declaration for pattern synonym ‘P’
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/83a32273ddca0d6c85db846be5e8fe9a37435d4d
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/83a32273ddca0d6c85db846be5e8fe9a37435d4d
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