Andrei Borzenkov pushed to branch wip/sand-witch/27423-gadt-parens at Glasgow Haskell Compiler / GHC

Commits:

13 changed files:

Changes:

  • changelog.d/allow-gadt-prefx-con-parens
    1 
    +section: language
    2 
    +synopsis: Allow parentheses in prefix GADT constructor declarations, as specified
    3 
    +  by GHC Proposal #402 "Stable GADT constructor syntax".
    4 
    +issues: #27423
    5 
    +mrs: !16321
    6 
    +
    7 
    +description: {
    8 
    +  Parenthesized types are now accepted in prefix GADT constructor declarations,
    9 
    +  even when they contain explicit ``forall`` quantifiers. For example:
    10 
    +
    11 
    +    data T where
    12 
    +      MkT :: (forall a. a -> b -> T)
    13 
    +
    14 
    +  This is equivalent to ``MkT :: forall {b}. (forall a. a -> b -> T)``, so the
    15 
    +  forall-or-nothing rule continues to be respected.
    16 
    +}

  • compiler/GHC/Hs/Decls.hs
    ... ... @@ -910,13 +910,28 @@ pprConDecl (ConDeclGADT { con_names = cons
    910 910 
                             , con_res_ty = res_ty, con_modifiers = mods, con_doc = doc })
    911 911 
       = pprMaybeWithDoc doc $ pprLHsModifiers mods <+> ppr_con_names (toList cons) <+> dcolon
    912 912 
         <+> (sep [pprHsOuterSigTyVarBndrs outer_bndrs
    913 
    +                <+> inner_bndrs_lguard
    913 914 
                     <+> hsep (map pprHsForAllTelescope inner_bndrs)
    914 915 
                     <+> pprLHsContext mcxt,
    915 
    -              sep (ppr_args args ++ [ppr res_ty]) ])
    916 
    +              sep (ppr_args args ++ [ppr res_ty]),
    917 
    +              inner_bndrs_rguard ])
    916 918 
       where
    917 919 
         ppr_args (PrefixConGADT _ args) = map (pprHsConDeclFieldWith (\arr tyDoc -> tyDoc <+> pprHsModifiedFunArr arr)) args
    918 920 
         ppr_args (RecConGADT _ fields) = [pprHsConDeclRecFields (unLoc fields) <+> arrow]
    919 921
    922 
    +    -- We may have inner binders without outer ones, for example:
    923 
    +    --   data D a where MkD :: forall. forall a. D a
    924 
    +    -- and
    925 
    +    --   data D a where MkD :: (forall a. D a)
    926 
    +    -- These cases have different outer_bndrs: explicit or implicit.
    927 
    +    -- We want to add an empty `forall.` or wrap type into parentheses
    928 
    +    -- to highlight the fact that binds in the question are indeed inner.
    929 
    +    (inner_bndrs_lguard, inner_bndrs_rguard)
    930 
    +      | null inner_bndrs = (empty, empty)
    931 
    +      | HsOuterImplicit{} <- outer_bndrs = (lparen, rparen)
    932 
    +      | HsOuterExplicit{hso_bndrs=[]} <- outer_bndrs = (text "forall" <+> text ".", empty)
    933 
    +      | otherwise = (empty, empty)
    934 
    +
    920 935 
     ppr_con_names :: (OutputableBndr a) => [GenLocated l a] -> SDoc
    921 936 
     ppr_con_names = pprWithCommas (pprPrefixOcc . unLoc)
    922 937

  • compiler/GHC/Hs/Type.hs
    ... ... @@ -898,12 +898,11 @@ splitLHsGadtTy (L _ sig_ty)
    898 898 
       | (outer_bndrs, sigma_ty) <- split_outer_bndrs sig_ty
    899 899 
       , (inner_bndrs, phi_ty)   <- split_inner_bndrs sigma_ty
    900 900 
       , (mb_ctxt, rho_ty)       <- splitLHsQualTy_KP phi_ty
    901 
    -  = case rho_ty of
    902 
    -      L _ (HsFunTy _ _ (L _ (XHsType HsRecTy{})) _) | not (null inner_bndrs)
    901 
    +  = if is_gadt_rec_ty rho_ty && not (null inner_bndrs)
    903 902 
             -- Bad! Record GADTs are not allowed to have inner_bndrs,
    904 903 
             -- undo the split to get a proper error message later
    905 
    -        -> (outer_bndrs, [], Nothing, sigma_ty)
    906 
    -      _ -> (outer_bndrs, inner_bndrs, mb_ctxt, rho_ty)
    904 
    +      then (outer_bndrs, [], Nothing, sigma_ty)
    905 
    +      else (outer_bndrs, inner_bndrs, mb_ctxt, rho_ty)
    907 906 
       where
    908 907 
         split_outer_bndrs :: HsSigType GhcPs -> (HsOuterSigTyVarBndrs GhcPs, LHsType GhcPs)
    909 908 
         split_outer_bndrs (HsSig{sig_bndrs = outer_bndrs, sig_body = body_ty}) =
    ... ... @@ -914,8 +913,17 @@ splitLHsGadtTy (L _ sig_ty)
    914 913 
                                           , hst_body = body })
    915 914 
           = let ~(teles, t) = split_inner_bndrs body
    916 915 
             in (tele:teles, t)
    916 
    +    split_inner_bndrs t@(L _ (HsParTy _ ty))
    917 
    +      | not (is_gadt_rec_ty ty)
    918 
    +      = split_inner_bndrs ty
    919 
    +      | otherwise
    920 
    +      = ([], t)
    917 921 
         split_inner_bndrs t = ([], t)
    918 922
    923 
    +    -- type of form {fld :: ty, ...} -> ResTy
    924 
    +    is_gadt_rec_ty (L _ (HsFunTy _ _ (L _ (XHsType HsRecTy{})) _)) = True
    925 
    +    is_gadt_rec_ty _ = False
    926 
    +
    919 927 
     -- | Decompose a type of the form @forall <tvs>. body@ into its constituent
    920 928 
     -- parts. Only splits type variable binders that
    921 929 
     -- were quantified invisibly (e.g., @forall a.@, with a dot).

  • testsuite/tests/gadt/T14320.stderr deleted
    1 
    -
    2 
    -T14320.hs:17:14: error: [GHC-71492]
    3 
    -    GADT constructor type signature cannot contain nested ‘forall’s or contexts
    4 
    -    In the definition of data constructor ‘TEBad’

  • testsuite/tests/gadt/T18191.hs
    ... ... @@ -2,15 +2,6 @@
    2 2 
     {-# LANGUAGE RankNTypes #-}
    3 3 
     module T18191 where
    4 4
    5 
    -data T where
    6 
    -  MkT :: (forall a. a -> b -> T)
    7 
    -
    8 
    -data S a where
    9 
    -  MkS :: (forall a. S a)
    10 
    -
    11 
    -data U a where
    12 
    -  MkU :: (Show a => U a)
    13 
    -
    14 5 
     data Z a where
    15 6 
       MkZ1 :: forall a. forall b. { unZ1 :: (a, b) } -> Z (a, b)
    16 7 
       MkZ2 :: Eq a => Eq b => { unZ1 :: (a, b) } -> Z (a, b)

  • testsuite/tests/gadt/T18191.stderr
    1 
    -
    2 
    -T18191.hs:6:11: error: [GHC-71492]
    3 
    -    • GADT constructor type signature cannot contain nested ‘forall’s or contexts
    4 
    -    • In the definition of data constructor ‘MkT’
    5 
    -
    6 
    -T18191.hs:9:11: error: [GHC-71492]
    7 
    -    • GADT constructor type signature cannot contain nested ‘forall’s or contexts
    8 
    -    • In the definition of data constructor ‘MkS’
    9 
    -
    10 
    -T18191.hs:12:11: error: [GHC-71492]
    11 
    -    • GADT constructor type signature cannot contain nested ‘forall’s or contexts
    12 
    -    • In the definition of data constructor ‘MkU’
    13 
    -
    14 
    -T18191.hs:15:21: error: [GHC-71492]
    1 
    +T18191.hs:6:21: error: [GHC-71492]
    15 2 
         • GADT constructor type signature cannot contain nested ‘forall’s or contexts
    16 3 
         • In the definition of data constructor ‘MkZ1’
    17 4
    18 
    -T18191.hs:15:31: error: [GHC-89246]
    5 
    +T18191.hs:6:31: error: [GHC-89246]
    19 6 
         • Record syntax is illegal here: {unZ1 :: (a, b)}
    20 7 
         • In the definition of data constructor ‘MkZ1’
    21 8
    22 
    -T18191.hs:16:19: error: [GHC-71492]
    9 
    +T18191.hs:7:19: error: [GHC-71492]
    23 10 
         • GADT constructor type signature cannot contain nested ‘forall’s or contexts
    24 11 
         • In the definition of data constructor ‘MkZ2’
    25 12
    26 
    -T18191.hs:16:27: error: [GHC-89246]
    13 
    +T18191.hs:7:27: error: [GHC-89246]
    27 14 
         • Record syntax is illegal here: {unZ1 :: (a, b)}
    28 15 
         • In the definition of data constructor ‘MkZ2’
    16 
    +

  • testsuite/tests/gadt/T27423a.hs
    1 
    +{-# LANGUAGE GADTs #-}
    2 
    +module T27423a where
    3 
    +
    4 
    +data G a where
    5 
    +  MkG1 :: a -> G a
    6 
    +  MkG2 :: (a -> G a)
    7 
    +  MkG3 :: forall a. a -> G a
    8 
    +  MkG4 :: forall a. (a -> G a)
    9 
    +
    10 
    +-- this is equivalent to `forall {b}. (forall a. a -> b -> T)`.
    11 
    +data T where
    12 
    +  MkT2 :: (forall a. a -> b -> T)
    13 
    +
    14 
    +-- this is equivalent to `forall. (forall a. S a)`.
    15 
    +data S a where
    16 
    +  MkS :: (forall a. S a)
    17 
    +
    18 
    +-- A forall and a context combined inside the same parentheses, with no
    19 
    +-- outer forall at all.
    20 
    +data Y a where
    21 
    +  MkY :: (forall a. Show a => a -> Y a)
    22 
    +
    23 
    +-- Multiple, redundant nested parentheses around the whole type should
    24 
    +-- be accepted.
    25 
    +data H a where
    26 
    +  MkH :: ((a -> H a))
    27 
    +
    28 
    +-- An unparenthesised outer forall together with an independent,
    29 
    +-- parenthesised inner forall.
    30 
    +data I a where
    31 
    +  MkI :: forall a. (forall b. I (b, a))

  • testsuite/tests/gadt/T27423b.hs
    1 
    +{-# LANGUAGE GADTs #-}
    2 
    +module T27423b where
    3 
    +
    4 
    +-- Record-style GADT constructors must remain unparenthesisable, per
    5 
    +-- GHC Proposal #402: this is out of scope for #27423 and should
    6 
    +-- continue to be rejected.
    7 
    +data T1 a where
    8 
    +  MkT1 :: ({ fld :: a } -> T1 a)
    9 
    +
    10 
    +data T2 a where
    11 
    +  MkT2 :: (forall a. { fld :: a } -> T2 a)
    12 
    +
    13 
    +-- Without parentheses, forall-or-nothing applies to the whole type, so
    14 
    +-- `b` is not implicitly quantified and this must be rejected.
    15 
    +data T3 where
    16 
    +  MkT3 :: forall a. a -> b -> T3

  • testsuite/tests/gadt/T27423b.stderr
    1 
    +T27423b.hs:8:12: error: [GHC-89246]
    2 
    +    • Record syntax is illegal here: {fld :: a}
    3 
    +    • In the definition of data constructor ‘MkT1’
    4 
    +
    5 
    +T27423b.hs:11:12: error: [GHC-71492]
    6 
    +    • GADT constructor type signature cannot contain nested ‘forall’s or contexts
    7 
    +    • In the definition of data constructor ‘MkT2’
    8 
    +
    9 
    +T27423b.hs:11:22: error: [GHC-89246]
    10 
    +    • Record syntax is illegal here: {fld :: a}
    11 
    +    • In the definition of data constructor ‘MkT2’
    12 
    +
    13 
    +T27423b.hs:16:26: error: [GHC-76037]
    14 
    +    Not in scope: type variable ‘b’
    15 
    +

  • testsuite/tests/gadt/all.T
    ... ... @@ -114,7 +114,7 @@ test('T7558', normal, compile, [''])
    114 114 
     test('T9380', normal, compile_and_run, [''])
    115 115 
     test('T12087', normal, compile_fail, [''])
    116 116 
     test('T12468', normal, compile_fail, [''])
    117 
    -test('T14320', normal, compile_fail, [''])
    117 
    +test('T14320', normal, compile, [''])
    118 118 
     test('T14719', normal, compile_fail, ['-fdiagnostics-show-caret'])
    119 119 
     test('T14808', normal, compile, [''])
    120 120 
     test('T15009', normal, compile, [''])
    ... ... @@ -132,3 +132,6 @@ test('T19847b', normal, compile, [''])
    132 132 
     test('T23022', normal, compile, ['-dcore-lint'])
    133 133 
     test('T23023', normal, compile_fail, ['-O -dcore-lint']) # todo: move this test?
    134 134 
     test('T23298', normal, compile_fail, [''])
    135 
    +
    136 
    +test('T27423a', normal, compile, [''])
    137 
    +test('T27423b', normal, compile_fail, [''])

  • testsuite/tests/printer/Makefile
    ... ... @@ -932,3 +932,8 @@ PprModifiers:
    932 932 
     PprQualifiedStrings:
    933 933 
     	$(CHECK_PPR)   $(LIBDIR) PprQualifiedStrings.hs
    934 934 
     	$(CHECK_EXACT) $(LIBDIR) PprQualifiedStrings.hs
    935 
    +
    936 
    +.PHONY: T27423c
    937 
    +T27423c:
    938 
    +	$(CHECK_PPR)   $(LIBDIR) T27423c.hs
    939 
    +	$(CHECK_EXACT) $(LIBDIR) T27423c.hs

  • testsuite/tests/printer/T27423c.hs
    1 
    +{-# LANGUAGE GADTs #-}
    2 
    +module T27423c where
    3 
    +
    4 
    +-- Exact-printing regression test
    5 
    +-- Not every declaration there would pass renamer without errors
    6 
    +data G a where
    7 
    +  MkG1 :: a -> G a
    8 
    +  MkG2 :: (a -> G a)
    9 
    +  MkG3 :: forall a. a -> G a
    10 
    +  MkG4 :: forall a. (a -> G a)
    11 
    +
    12 
    +data T where
    13 
    +  MkT1 :: forall a. a -> b -> T
    14 
    +  MkT2 :: (forall a. a -> b -> T)
    15 
    +
    16 
    +data S a where
    17 
    +  MkS :: (forall a. S a)
    18 
    +
    19 
    +data U a where
    20 
    +  MkU :: (Show a => U a)
    21 
    +
    22 
    +data V a where
    23 
    +  MkV1 :: ((a -> V a))
    24 
    +  MkV2 :: forall a. (forall b. V (b, a))
    25 
    +  MkV3 :: (forall a. Show a => a -> V a)
    26 
    +  MkV4 :: forall a. ((forall b. (Show a => a -> (b -> V a))))

  • testsuite/tests/printer/all.T
    ... ... @@ -223,3 +223,5 @@ test('TestLevelImports', [ignore_stderr, req_ppr_deps], makefile_test, ['TestLev
    223 223 
     test('TestNamedDefaults', [ignore_stderr, req_ppr_deps], makefile_test, ['TestNamedDefaults'])
    224 224 
     test('PprModifiers', [ignore_stderr,req_ppr_deps], makefile_test, ['PprModifiers'])
    225 225 
     test('PprQualifiedStrings', [ignore_stderr,req_ppr_deps], makefile_test, ['PprQualifiedStrings'])
    226 
    +
    227 
    +test('T27423c', [ignore_stderr,req_ppr_deps], makefile_test, ['T27423c'])

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