Vladislav Zavialov pushed to branch wip/int-index/visible-forall-gadts at Glasgow Haskell Compiler / GHC
Commits:
-
79866e89
by Vladislav Zavialov at 2025-06-10T12:01:53+03:00
3 changed files:
- compiler/Language/Haskell/Syntax/Decls.hs
- docs/users_guide/9.14.1-notes.rst
- docs/users_guide/exts/required_type_arguments.rst
Changes:
| ... | ... | @@ -970,9 +970,10 @@ data ConDecl pass |
| 970 | 970 | -- The following fields describe the type after the '::'
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| 971 | 971 | -- See Note [GADT abstract syntax]
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| 972 | 972 | , con_outer_bndrs :: XRec pass (HsOuterSigTyVarBndrs pass)
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| 973 | - -- ^ The outermost type variable binders, be they explicit or
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| 974 | - -- implicit. The 'XRec' is used to anchor exact print
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| 975 | - -- annotations, AnnForall and AnnDot.
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| 973 | + -- ^ The outermost type variable binders, be they explicit or implicit;
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| 974 | + -- cf. HsSigType that also stores the outermost sig_bndrs separately
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| 975 | + -- from the forall telescopes in sig_body.
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| 976 | + -- See Note [Representing type signatures] in Language.Haskell.Syntax.Type
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| 976 | 977 | , con_inner_bndrs :: [HsForAllTelescope pass]
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| 977 | 978 | -- ^ The forall telescopes other than the outermost invisible forall.
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| 978 | 979 | , con_mb_cxt :: Maybe (LHsContext pass) -- ^ User-written context (if any)
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| ... | ... | @@ -72,6 +72,18 @@ Language |
| 72 | 72 | |
| 73 | 73 | * The :extension:`MonadComprehensions` extension now implies :extension:`ParallelListComp` as was originally intended (see `Monad Comprehensions <https://ghc.gitlab.haskell.org/ghc/doc/users_guide/exts/monad_comprehensions.html>`_).
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| 74 | 74 | |
| 75 | +* In accordance with `GHC Proposal #281 <https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0281-visible-forall.rst>`_,
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| 76 | + section 4.7 "Data constructors", the :extension:`RequiredTypeArguments`
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| 77 | + extension now allows visible forall in types of data constructors
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| 78 | + (:ghc-ticket:`25127`). The following declaration is now accepted by GHC:
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| 79 | + |
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| 80 | + ::
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| 81 | + |
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| 82 | + data T a where
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| 83 | + Typed :: forall a -> a -> T a
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| 84 | + |
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| 85 | + See :ref:`visible-forall-in-gadts` for details.
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| 86 | + |
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| 75 | 87 | Compiler
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| 76 | 88 | ~~~~~~~~
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| 77 | 89 |
| ... | ... | @@ -428,6 +428,8 @@ The :extension:`RequiredTypeArguments` extension does not add dependent |
| 428 | 428 | functions, which would be a much bigger step. Rather :extension:`RequiredTypeArguments`
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| 429 | 429 | just makes it possible for the type arguments of a function to be compulsory.
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| 430 | 430 | |
| 431 | +.. _visible-forall-in-gadts:
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| 432 | + |
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| 431 | 433 | Visible forall in GADTs
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| 432 | 434 | ~~~~~~~~~~~~~~~~~~~~~~~
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| 433 | 435 |