Simon Jakobi pushed to branch wip/sjakobi/T27732-type-data-field-annotations at Glasgow Haskell Compiler / GHC Commits: 728dcc2e by Simon Jakobi at 2026-08-22T00:06:33+02:00 Reject `~` and UNPACK annotations on type data fields Widen restriction (R3) of Note [Type data declarations] to any strictness or unpackedness annotation — none of them make sense at the type level — and generalize the check and error message accordingly. Fixes #27732 Assisted-by: Claude Fable 5 - - - - - 15 changed files: - + changelog.d/27732 - compiler/GHC/Rename/Module.hs - compiler/GHC/Tc/Errors/Types.hs - docs/users_guide/exts/type_data.rst - + testsuite/tests/type-data/should_fail/T27732a.hs - + testsuite/tests/type-data/should_fail/T27732a.stderr - + testsuite/tests/type-data/should_fail/T27732b.hs - + testsuite/tests/type-data/should_fail/T27732b.stderr - + testsuite/tests/type-data/should_fail/T27732c.hs - + testsuite/tests/type-data/should_fail/T27732c.stderr - + testsuite/tests/type-data/should_fail/T27732d.hs - + testsuite/tests/type-data/should_fail/T27732d.stderr - testsuite/tests/type-data/should_fail/TDStrictnessGADT.stderr - testsuite/tests/type-data/should_fail/TDStrictnessH98.stderr - testsuite/tests/type-data/should_fail/all.T Changes: ===================================== changelog.d/27732 ===================================== @@ -0,0 +1,8 @@ +section: language +synopsis: Reject `~` and UNPACK annotations on type data fields +description: + ``type data`` declarations (:extension:`TypeData`) now reject any + strictness or unpackedness annotation on constructor fields. + Previously only ``!`` was rejected. +mrs: !16536 +issues: #27732 ===================================== compiler/GHC/Rename/Module.hs ===================================== @@ -71,7 +71,7 @@ import GHC.Data.Graph.Directed ( SCC, flattenSCC, Node(..) , stronglyConnCompFromEdgedVerticesUniq ) import GHC.Data.OrdList import qualified GHC.LanguageExtensions as LangExt -import GHC.Core.DataCon ( isSrcStrict ) +import GHC.Core.DataCon ( SrcStrictness(..), SrcUnpackedness(..) ) import Control.Monad import Data.Bifunctor ( first ) @@ -2116,8 +2116,8 @@ rnDataDefn doc (HsDataDefn { dd_cType = cType, dd_ctxt = context, dd_cons = cond = do { ; when (has_labelled_fields condecl) $ failWith $ TcRnTypeDataForbids TypeDataForbidsLabelledFields - ; when (has_strictness_flags condecl) $ - failWith $ TcRnTypeDataForbids TypeDataForbidsStrictnessAnnotations + ; when (has_field_annotations condecl) $ + failWith $ TcRnTypeDataForbids TypeDataForbidsFieldAnnotations } has_labelled_fields (ConDeclGADT { con_g_args = RecConGADT _ _ }) = True @@ -2125,13 +2125,16 @@ rnDataDefn doc (HsDataDefn { dd_cType = cType, dd_ctxt = context, dd_cons = cond = not (null (unLoc flds)) has_labelled_fields _ = False - has_strictness_flags condecl - = any isSrcStrict (con_arg_bangs condecl) + has_field_annotations condecl + = any is_annotated (con_arg_fields condecl) + where + is_annotated (CDF { cdf_bang = bang, cdf_unpack = unpack }) + = bang /= NoSrcStrict || unpack /= NoSrcUnpack - con_arg_bangs (ConDeclGADT { con_g_args = PrefixConGADT _ args }) = map cdf_bang args - con_arg_bangs (ConDeclH98 { con_args = PrefixCon _ args }) = map cdf_bang args - con_arg_bangs (ConDeclH98 { con_args = InfixCon _ arg1 arg2 }) = [cdf_bang arg1, cdf_bang arg2] - con_arg_bangs _ = [] + con_arg_fields (ConDeclGADT { con_g_args = PrefixConGADT _ args }) = args + con_arg_fields (ConDeclH98 { con_args = PrefixCon _ args }) = args + con_arg_fields (ConDeclH98 { con_args = InfixCon _ arg1 arg2 }) = [arg1, arg2] + con_arg_fields _ = [] {- Note [Type data declarations] @@ -2166,8 +2169,9 @@ preceded by `type`, with the following restrictions: (R2) There are no labelled fields. Perhaps these could be supported using type families, but they are omitted for now. -(R3) There are no strictness flags, because they don't make sense at - the type level. +(R3) There are no strictness or unpackedness annotations (!, ~, + {-# UNPACK #-}, {-# NOUNPACK #-}), because they don't make sense + at the type level. (R4) The types of the constructors contain no constraints. ===================================== compiler/GHC/Tc/Errors/Types.hs ===================================== @@ -2865,6 +2865,10 @@ data TcRnMessage where type-data/should_fail/TDRecordsH98 type-data/should_fail/TDStrictnessGADT type-data/should_fail/TDStrictnessH98 + type-data/should_fail/T27732a + type-data/should_fail/T27732b + type-data/should_fail/T27732c + type-data/should_fail/T27732d -} TcRnTypeDataForbids :: !TypeDataForbids -> TcRnMessage @@ -4523,15 +4527,15 @@ data ZonkerMessage where data TypeDataForbids = TypeDataForbidsDatatypeContexts | TypeDataForbidsLabelledFields - | TypeDataForbidsStrictnessAnnotations + | TypeDataForbidsFieldAnnotations | TypeDataForbidsDerivingClauses deriving Generic instance Outputable TypeDataForbids where - ppr TypeDataForbidsDatatypeContexts = text "Data type contexts" - ppr TypeDataForbidsLabelledFields = text "Labelled fields" - ppr TypeDataForbidsStrictnessAnnotations = text "Strictness flags" - ppr TypeDataForbidsDerivingClauses = text "Deriving clauses" + ppr TypeDataForbidsDatatypeContexts = text "Data type contexts" + ppr TypeDataForbidsLabelledFields = text "Labelled fields" + ppr TypeDataForbidsFieldAnnotations = text "Strictness or unpackedness annotations" + ppr TypeDataForbidsDerivingClauses = text "Deriving clauses" -- | Specifies which back ends can handle a requested foreign import or export type ExpectedBackends = [Backend] ===================================== docs/users_guide/exts/type_data.rst ===================================== @@ -33,7 +33,7 @@ either an ordinary algebraic data type or a GADT, prefixed with the keyword ``type``, except that it may not contain a datatype context (even with :extension:`DatatypeContexts`), labelled fields, -strictness flags, or +:ref:`strictness <strict-haskell>` or :ref:`unpackedness <unpack-pragma>` annotations, or a ``deriving`` clause. The only constraints permitted in the types of constructors are ===================================== testsuite/tests/type-data/should_fail/T27732a.hs ===================================== @@ -0,0 +1,4 @@ +{-# LANGUAGE TypeData, LazyFieldAnnotations #-} +module T27732a where + +type data T a = Cons ~a ===================================== testsuite/tests/type-data/should_fail/T27732a.stderr ===================================== @@ -0,0 +1,3 @@ +T27732a.hs:4:17: error: [GHC-67297] + Strictness or unpackedness annotations are not allowed in type data declarations. + ===================================== testsuite/tests/type-data/should_fail/T27732b.hs ===================================== @@ -0,0 +1,5 @@ +{-# LANGUAGE TypeData, LazyFieldAnnotations #-} +module T27732b where + +type data T a where + Cons :: ~a -> T a ===================================== testsuite/tests/type-data/should_fail/T27732b.stderr ===================================== @@ -0,0 +1,3 @@ +T27732b.hs:5:6: error: [GHC-67297] + Strictness or unpackedness annotations are not allowed in type data declarations. + ===================================== testsuite/tests/type-data/should_fail/T27732c.hs ===================================== @@ -0,0 +1,4 @@ +{-# LANGUAGE TypeData #-} +module T27732c where + +type data T a = Cons {-# UNPACK #-} a ===================================== testsuite/tests/type-data/should_fail/T27732c.stderr ===================================== @@ -0,0 +1,3 @@ +T27732c.hs:4:17: error: [GHC-67297] + Strictness or unpackedness annotations are not allowed in type data declarations. + ===================================== testsuite/tests/type-data/should_fail/T27732d.hs ===================================== @@ -0,0 +1,4 @@ +{-# LANGUAGE TypeData #-} +module T27732d where + +type data T a = Cons {-# NOUNPACK #-} a ===================================== testsuite/tests/type-data/should_fail/T27732d.stderr ===================================== @@ -0,0 +1,3 @@ +T27732d.hs:4:17: error: [GHC-67297] + Strictness or unpackedness annotations are not allowed in type data declarations. + ===================================== testsuite/tests/type-data/should_fail/TDStrictnessGADT.stderr ===================================== @@ -1,3 +1,3 @@ +TDStrictnessGADT.hs:5:6: error: [GHC-67297] + Strictness or unpackedness annotations are not allowed in type data declarations. -TDStrictnessGADT.hs:5:6: [GHC-67297] - Strictness flags are not allowed in type data declarations. ===================================== testsuite/tests/type-data/should_fail/TDStrictnessH98.stderr ===================================== @@ -1,3 +1,3 @@ +TDStrictnessH98.hs:4:17: error: [GHC-67297] + Strictness or unpackedness annotations are not allowed in type data declarations. -TDStrictnessH98.hs:4:17: [GHC-67297] - Strictness flags are not allowed in type data declarations. ===================================== testsuite/tests/type-data/should_fail/all.T ===================================== @@ -13,3 +13,7 @@ test('TDStrictnessGADT', normal, compile_fail, ['']) test('TDStrictnessH98', normal, compile_fail, ['']) test('TDTagToEnum', normal, compile_fail, ['']) test('T22332b', normal, compile_fail, ['']) +test('T27732a', normal, compile_fail, ['']) +test('T27732b', normal, compile_fail, ['']) +test('T27732c', normal, compile_fail, ['']) +test('T27732d', normal, compile_fail, ['']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/728dcc2e4be9f8d5df8b38db3e880296... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/728dcc2e4be9f8d5df8b38db3e880296... 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