diff options
| -rw-r--r-- | compiler/GHC/Driver/Hooks.hs | 33 | ||||
| -rw-r--r-- | compiler/GHC/HsToCore/Types.hs | 10 |
2 files changed, 37 insertions, 6 deletions
diff --git a/compiler/GHC/Driver/Hooks.hs b/compiler/GHC/Driver/Hooks.hs index f6aca818f9..36b97502cb 100644 --- a/compiler/GHC/Driver/Hooks.hs +++ b/compiler/GHC/Driver/Hooks.hs @@ -3,7 +3,7 @@ -- NB: this module is SOURCE-imported by DynFlags, and should primarily -- refer to *types*, rather than *code* -{-# LANGUAGE CPP, RankNTypes #-} +{-# LANGUAGE CPP, RankNTypes, TypeFamilies #-} module GHC.Driver.Hooks ( Hooks @@ -11,6 +11,7 @@ module GHC.Driver.Hooks , lookupHook , getHooked -- the hooks: + , DsForeignsHook , dsForeignsHook , tcForeignImportsHook , tcForeignExportsHook @@ -36,9 +37,7 @@ import GHC.Driver.Types import GHC.Hs.Decls import GHC.Hs.Binds import GHC.Hs.Expr -import GHC.Data.OrdList import GHC.Tc.Types -import GHC.HsToCore.Types import GHC.Data.Bag import GHC.Types.Name.Reader import GHC.Types.Name @@ -59,6 +58,7 @@ import GHC.Hs.Extension import GHC.StgToCmm.Types (ModuleLFInfos) import Data.Maybe +import qualified Data.Kind {- ************************************************************************ @@ -90,9 +90,32 @@ emptyHooks = Hooks , cmmToRawCmmHook = Nothing } +{- Note [The Decoupling Abstract Data Hack] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The "Abstract Data" idea is due to Richard Eisenberg in +https://gitlab.haskell.org/ghc/ghc/-/merge_requests/1957, where the pattern is +described in more detail. + +Here we use it as a temporary measure to break the dependency from the Parser on +the Desugarer until the parser is free of DynFlags. We introduced a nullary type +family @DsForeignsook@, whose single definition is in GHC.HsToCore.Types, where +we instantiate it to + + [LForeignDecl GhcTc] -> DsM (ForeignStubs, OrdList (Id, CoreExpr)) + +In doing so, the Hooks module (which is an hs-boot dependency of DynFlags) can +be decoupled from its use of the DsM definition in GHC.HsToCore.Types. Since +both DsM and the definition of @ForeignsHook@ live in the same module, there is +virtually no difference for plugin authors that want to write a foreign hook. +-} + +-- See Note [The Decoupling Abstract Data Hack] +type family DsForeignsHook :: Data.Kind.Type + data Hooks = Hooks - { dsForeignsHook :: Maybe ([LForeignDecl GhcTc] - -> DsM (ForeignStubs, OrdList (Id, CoreExpr))) + { dsForeignsHook :: Maybe DsForeignsHook + -- ^ Actual type: + -- @Maybe ([LForeignDecl GhcTc] -> DsM (ForeignStubs, OrdList (Id, CoreExpr)))@ , tcForeignImportsHook :: Maybe ([LForeignDecl GhcRn] -> TcM ([Id], [LForeignDecl GhcTc], Bag GlobalRdrElt)) , tcForeignExportsHook :: Maybe ([LForeignDecl GhcRn] diff --git a/compiler/GHC/HsToCore/Types.hs b/compiler/GHC/HsToCore/Types.hs index 26f6a6af79..b99970f55f 100644 --- a/compiler/GHC/HsToCore/Types.hs +++ b/compiler/GHC/HsToCore/Types.hs @@ -1,3 +1,5 @@ +{-# LANGUAGE TypeFamilies, UndecidableInstances #-} + -- | Various types used during desugaring. module GHC.HsToCore.Types ( DsM, DsLclEnv(..), DsGblEnv(..), @@ -10,13 +12,17 @@ import GHC.Types.CostCentre.State import GHC.Types.Name.Env import GHC.Types.SrcLoc import GHC.Types.Var -import GHC.Hs (HsExpr, GhcTc) +import GHC.Hs (LForeignDecl, HsExpr, GhcTc) import GHC.Tc.Types (TcRnIf, IfGblEnv, IfLclEnv, CompleteMatches) import {-# SOURCE #-} GHC.HsToCore.PmCheck.Types (Nablas) +import GHC.Core (CoreExpr) import GHC.Core.FamInstEnv import GHC.Utils.Error import GHC.Utils.Outputable as Outputable import GHC.Unit.Module +import GHC.Driver.Hooks (DsForeignsHook) +import GHC.Data.OrdList (OrdList) +import GHC.Driver.Types (ForeignStubs) {- ************************************************************************ @@ -75,3 +81,5 @@ data DsMetaVal -- | Desugaring monad. See also 'TcM'. type DsM = TcRnIf DsGblEnv DsLclEnv +-- See Note [The Decoupling Abstract Data Hack] +type instance DsForeignsHook = [LForeignDecl GhcTc] -> DsM (ForeignStubs, OrdList (Id, CoreExpr)) |