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|
{-# LANGUAGE RecordWildCards #-}
{-# OPTIONS_HADDOCK show-extensions #-}
module Internal
( -- * Create new constraints
TcPlugin.newWanted
, newGiven
-- * Creating evidence
, evByFiat
-- * Lookup
, lookupModule
, lookupName
-- * Trace state of the plugin
, tracePlugin
-- * Substitutions
, flattenGivens
, mkSubst
, mkSubst'
, substType
, substCt
)
where
import GHC.Driver.Config.Finder (initFinderOpts)
import GHC.Tc.Plugin (TcPluginM, lookupOrig, tcPluginTrace)
import qualified GHC.Tc.Plugin as TcPlugin
(newWanted, getTopEnv, tcPluginIO, findImportedModule)
import GHC.Tc.Types (TcPlugin(..), TcPluginSolveResult(..))
import Control.Arrow (first, second)
import Data.Function (on)
import Data.List (groupBy, partition, sortOn)
import GHC.Tc.Utils.TcType (TcType)
import Data.Maybe (mapMaybe)
import GhcApi.Constraint (Ct(..))
import GhcApi.GhcPlugins
import Internal.Type (substType)
import Internal.Constraint (newGiven, flatToCt, mkSubst, overEvidencePredType)
import Internal.Evidence (evByFiat)
-- | Find a module
lookupModule :: ModuleName -- ^ Name of the module
-> FastString -- ^ Name of the package containing the module.
-- NOTE: This value is ignored on ghc>=8.0.
-> TcPluginM Module
lookupModule mod_nm _pkg = do
hsc_env <- TcPlugin.getTopEnv
let fc = hsc_FC hsc_env
dflags = hsc_dflags hsc_env
fopts = initFinderOpts dflags
units = hsc_units hsc_env
mhome_unit = hsc_home_unit_maybe hsc_env
found_module <- TcPlugin.tcPluginIO $ findPluginModule fc fopts units
mhome_unit mod_nm
case found_module of
Found _ h -> return h
_ -> do
let pkg_qual = maybe NoPkgQual (ThisPkg . homeUnitId) mhome_unit
found_module' <- TcPlugin.findImportedModule mod_nm pkg_qual
case found_module' of
Found _ h -> return h
_ -> panicDoc "Couldn't find module" (ppr mod_nm)
-- | Find a 'Name' in a 'Module' given an 'OccName'
lookupName :: Module -> OccName -> TcPluginM Name
lookupName = lookupOrig
-- | Print out extra information about the initialisation, stop, and every run
-- of the plugin when @-ddump-tc-trace@ is enabled.
tracePlugin :: String -> TcPlugin -> TcPlugin
tracePlugin s TcPlugin{..} = TcPlugin { tcPluginInit = traceInit
, tcPluginSolve = traceSolve
, tcPluginRewrite = tcPluginRewrite
, tcPluginStop = traceStop
}
where
traceInit = do
tcPluginTrace ("tcPluginInit " ++ s) empty >> tcPluginInit
traceStop z = tcPluginTrace ("tcPluginStop " ++ s) empty >> tcPluginStop z
traceSolve z ev given wanted = do
tcPluginTrace ("tcPluginSolve start " ++ s)
(text "given =" <+> ppr given
$$ text "wanted =" <+> ppr wanted)
r <- tcPluginSolve z ev given wanted
case r of
TcPluginOk solved new
-> tcPluginTrace ("tcPluginSolve ok " ++ s)
(text "solved =" <+> ppr solved
$$ text "new =" <+> ppr new)
TcPluginContradiction bad
-> tcPluginTrace ("tcPluginSolve contradiction " ++ s)
(text "bad =" <+> ppr bad)
TcPluginSolveResult bad solved new
-> tcPluginTrace ("tcPluginSolveResult " ++ s)
(text "solved =" <+> ppr solved
$$ text "bad =" <+> ppr bad
$$ text "new =" <+> ppr new)
return r
-- | Flattens evidence of constraints by substituting each others equalities.
--
-- __NB:__ Should only be used on /[G]iven/ constraints!
--
-- __NB:__ Doesn't flatten under binders
flattenGivens :: [Ct] -> [Ct]
flattenGivens givens =
mapMaybe flatToCt flat ++ map (substCt subst') givens
where
subst = mkSubst' givens
(flat,subst')
= second (map fst . concat)
$ partition ((>= 2) . length)
$ groupBy ((==) `on` (fst.fst))
$ sortOn (fst.fst) subst
-- | Create flattened substitutions from type equalities, i.e. the substitutions
-- have been applied to each others right hand sides.
mkSubst' :: [Ct] -> [((TcTyVar,TcType),Ct)]
mkSubst' = foldr substSubst [] . mapMaybe mkSubst
where
substSubst :: ((TcTyVar,TcType),Ct)
-> [((TcTyVar,TcType),Ct)]
-> [((TcTyVar,TcType),Ct)]
substSubst ((tv,t),ct) s = ((tv,substType (map fst s) t),ct)
: map (first (second (substType [(tv,t)]))) s
-- | Apply substitution in the evidence of Cts
substCt :: [(TcTyVar, TcType)] -> Ct -> Ct
substCt subst = overEvidencePredType (substType subst)
|
