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| author | Vladislav Zavialov <vlad.z.4096@gmail.com> | 2023-01-09 21:45:15 +0300 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2023-01-11 00:58:03 -0500 |
| commit | bc1257750f507218059ac6bad05d9c96a8b88d67 (patch) | |
| tree | 25890b5ab5dc528f0907816d1d0e1a4895011378 /compiler | |
| parent | 5f17e21af6368ec0e615af7de714a3194181f46a (diff) | |
| download | haskell-bc1257750f507218059ac6bad05d9c96a8b88d67.tar.gz | |
Introduce the TypeAbstractions language flag
GHC Proposals #448 "Modern scoped type variables"
and #425 "Invisible binders in type declarations"
introduce a new language extension flag: TypeAbstractions.
Part of the functionality guarded by this flag has already been
implemented, namely type abstractions in constructor patterns, but it
was guarded by a combination of TypeApplications and ScopedTypeVariables
instead of a dedicated language extension flag.
This patch does the following:
* introduces a new language extension flag TypeAbstractions
* requires TypeAbstractions for @a-syntax in constructor patterns
instead of TypeApplications and ScopedTypeVariables
* creates a User's Guide page for TypeAbstractions and
moves the "Type Applications in Patterns" section there
To avoid a breaking change, the new flag is implied by
ScopedTypeVariables and is retroactively added to GHC2021.
Metric Decrease:
MultiLayerModulesTH_OneShot
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/GHC/Driver/Session.hs | 5 | ||||
| -rw-r--r-- | compiler/GHC/Rename/Pat.hs | 8 |
2 files changed, 8 insertions, 5 deletions
diff --git a/compiler/GHC/Driver/Session.hs b/compiler/GHC/Driver/Session.hs index 29dff3650f..57d89a15b1 100644 --- a/compiler/GHC/Driver/Session.hs +++ b/compiler/GHC/Driver/Session.hs @@ -1412,6 +1412,7 @@ languageExtensions (Just GHC2021) LangExt.PostfixOperators, LangExt.RankNTypes, LangExt.ScopedTypeVariables, + LangExt.TypeAbstractions, -- implied by ScopedTypeVariables according to GHC Proposal #448 "Modern Scoped Type Variables" LangExt.StandaloneDeriving, LangExt.StandaloneKindSignatures, LangExt.TupleSections, @@ -3766,6 +3767,7 @@ xFlagsDeps = [ flagSpec "TraditionalRecordSyntax" LangExt.TraditionalRecordSyntax, flagSpec "TransformListComp" LangExt.TransformListComp, flagSpec "TupleSections" LangExt.TupleSections, + flagSpec "TypeAbstractions" LangExt.TypeAbstractions, flagSpec "TypeApplications" LangExt.TypeApplications, flagSpec "TypeData" LangExt.TypeData, depFlagSpec' "TypeInType" LangExt.TypeInType @@ -3902,6 +3904,9 @@ impliedXFlags , (LangExt.MultiParamTypeClasses, turnOn, LangExt.ConstrainedClassMethods) -- c.f. #7854 , (LangExt.TypeFamilyDependencies, turnOn, LangExt.TypeFamilies) + -- In accordance with GHC Proposal #448 "Modern Scoped Type Variables" + , (LangExt.ScopedTypeVariables, turnOn, LangExt.TypeAbstractions) + , (LangExt.RebindableSyntax, turnOff, LangExt.ImplicitPrelude) -- NB: turn off! , (LangExt.DerivingVia, turnOn, LangExt.DerivingStrategies) diff --git a/compiler/GHC/Rename/Pat.hs b/compiler/GHC/Rename/Pat.hs index 9c4f3dd9fb..169c2e508c 100644 --- a/compiler/GHC/Rename/Pat.hs +++ b/compiler/GHC/Rename/Pat.hs @@ -640,16 +640,14 @@ rnConPatAndThen mk con (PrefixCon tyargs pats) where check_lang_exts :: RnM () check_lang_exts = do - scoped_tyvars <- xoptM LangExt.ScopedTypeVariables - type_app <- xoptM LangExt.TypeApplications - unless (scoped_tyvars && type_app) $ + type_abs <- xoptM LangExt.TypeAbstractions + unless type_abs $ case listToMaybe tyargs of Nothing -> pure () Just tyarg -> addErr $ mkTcRnUnknownMessage $ mkPlainError noHints $ hang (text "Illegal visible type application in a pattern:" <+> quotes (ppr tyarg)) - 2 (text "Both ScopedTypeVariables and TypeApplications are" - <+> text "required to use this feature") + 2 (text "Perhaps you intended to use TypeAbstractions") rnConPatTyArg (HsConPatTyArg at t) = do t' <- liftCpsWithCont $ rnHsPatSigTypeBindingVars HsTypeCtx t return (HsConPatTyArg at t') |