import Maybes
import ErrUtils
import Finder
-import UniqFM
+import LazyUniqFM
import StaticFlags
import Outputable
import BinIface
-- interface; it will call the Finder again, but the ModLocation will be
-- cached from the first search.
hsc_env <- getTopEnv
- res <- ioToIOEnv $ findImportedModule hsc_env mod Nothing
+ res <- liftIO $ findImportedModule hsc_env mod Nothing
case res of
Found _ mod -> do
mb_iface <- initIfaceTcRn $ loadInterface doc mod (ImportByUser want_boot)
-> Bool -- these are family instance-modules
-> TcM ()
loadOrphanModules mods isFamInstMod
- | null mods = returnM ()
+ | null mods = return ()
| otherwise = initIfaceTcRn $
do { traceIf (text "Loading orphan modules:" <+>
fsep (map ppr mods))
- ; mappM_ load mods
- ; returnM () }
+ ; mapM_ load mods
+ ; return () }
where
load mod = loadSysInterface (mk_doc mod) mod
mk_doc mod
; dflags <- getDOpts
; case lookupIfaceByModule dflags hpt (eps_PIT eps) mod of {
Just iface
- -> returnM (Succeeded iface) ; -- Already loaded
+ -> return (Succeeded iface) ; -- Already loaded
-- The (src_imp == mi_boot iface) test checks that the already-loaded
-- interface isn't a boot iface. This can conceivably happen,
-- if an earlier import had a before we got to real imports. I think.
-- Not found, so add an empty iface to
-- the EPS map so that we don't look again
- ; returnM (Failed err) } ;
+ ; return (Failed err) } ;
-- Found and parsed!
Succeeded (iface, file_path) -- Sanity check:
modulePackageId (mi_module iface) == thisPackage dflags,
-- a home-package module...
Nothing <- mb_dep -- that we know nothing about
- -> returnM (Failed (badDepMsg mod))
+ -> return (Failed (badDepMsg mod))
| otherwise ->
fam_inst_env,
eps_stats = addEpsInStats (eps_stats eps)
(length new_eps_decls)
- (length new_eps_insts) (length new_eps_rules) }
+ (length new_eps_insts)
+ (length new_eps_rules) }
; return (Succeeded final_iface)
}}}}
; thing <- forkM doc $ do { bumpDeclStats main_name
; tcIfaceDecl ignore_prags decl }
- -- Populate the type environment with the implicitTyThings too.
- --
- -- Note [Tricky iface loop]
- -- ~~~~~~~~~~~~~~~~~~~~~~~~
- -- The delicate point here is that 'mini-env' should be
- -- buildable from 'thing' without demanding any of the things 'forkM'd
- -- by tcIfaceDecl. For example
- -- class C a where { data T a; op :: T a -> Int }
- -- We return the bindings
- -- [("C", <cls>), ("T", lookup env "T"), ("op", lookup env "op")]
- -- The call (lookup env "T") must return the tycon T without first demanding
- -- op; because getting the latter will look up T, hence loop.
- --
- -- Of course, there is no reason in principle why (lookup env "T") should demand
- -- anything do to with op, but take care:
- -- (a) implicitTyThings, and
- -- (b) getOccName of all the things returned by implicitThings,
- -- must not depend on any of the nested type-checks
- --
- -- All a bit too finely-balanced for my liking.
-
+ -- Populate the type environment with the implicitTyThings too.
+ --
+ -- Note [Tricky iface loop]
+ -- ~~~~~~~~~~~~~~~~~~~~~~~~
+ -- Summary: The delicate point here is that 'mini-env' must be
+ -- buildable from 'thing' without demanding any of the things
+ -- 'forkM'd by tcIfaceDecl.
+ --
+ -- In more detail: Consider the example
+ -- data T a = MkT { x :: T a }
+ -- The implicitTyThings of T are: [ <datacon MkT>, <selector x>]
+ -- (plus their workers, wrappers, coercions etc etc)
+ --
+ -- We want to return an environment
+ -- [ "MkT" -> <datacon MkT>, "x" -> <selector x>, ... ]
+ -- (where the "MkT" is the *Name* associated with MkT, etc.)
+ --
+ -- We do this by mapping the implict_names to the associated
+ -- TyThings. By the invariant on ifaceDeclSubBndrs and
+ -- implicitTyThings, we can use getOccName on the implicit
+ -- TyThings to make this association: each Name's OccName should
+ -- be the OccName of exactly one implictTyThing. So the key is
+ -- to define a "mini-env"
+ --
+ -- [ 'MkT' -> <datacon MkT>, 'x' -> <selector x>, ... ]
+ -- where the 'MkT' here is the *OccName* associated with MkT.
+ --
+ -- However, there is a subtlety: due to how type checking needs
+ -- to be staged, we can't poke on the forkM'd thunks inside the
+ -- implictTyThings while building this mini-env.
+ -- If we poke these thunks too early, two problems could happen:
+ -- (1) When processing mutually recursive modules across
+ -- hs-boot boundaries, poking too early will do the
+ -- type-checking before the recursive knot has been tied,
+ -- so things will be type-checked in the wrong
+ -- environment, and necessary variables won't be in
+ -- scope.
+ --
+ -- (2) Looking up one OccName in the mini_env will cause
+ -- others to be looked up, which might cause that
+ -- original one to be looked up again, and hence loop.
+ --
+ -- The code below works because of the following invariant:
+ -- getOccName on a TyThing does not force the suspended type
+ -- checks in order to extract the name. For example, we don't
+ -- poke on the "T a" type of <selector x> on the way to
+ -- extracting <selector x>'s OccName. Of course, there is no
+ -- reason in principle why getting the OccName should force the
+ -- thunks, but this means we need to be careful in
+ -- implicitTyThings and its helper functions.
+ --
+ -- All a bit too finely-balanced for my liking.
+
+ -- This mini-env and lookup function mediates between the
+ -- *Name*s n and the map from *OccName*s to the implicit TyThings
; let mini_env = mkOccEnv [(getOccName t, t) | t <- implicitTyThings thing]
lookup n = case lookupOccEnv mini_env (getOccName n) of
Just thing -> thing
Nothing ->
pprPanic "loadDecl" (ppr main_name <+> ppr n $$ ppr (decl))
- ; returnM $ (main_name, thing) : [(n, lookup n) | n <- implicit_names]
+ ; return $ (main_name, thing) :
+ -- uses the invariant that implicit_names and
+ -- implictTyThings are bijective
+ [(n, lookup n) | n <- implicit_names]
}
- -- We build a list from the *known* names, with (lookup n) thunks
- -- as the TyThings. That way we can extend the PTE without poking the
- -- thunks
where
doc = ptext SLIT("Declaration for") <+> ppr (ifName decl)
-- Check for GHC.Prim, and return its static interface
; dflags <- getDOpts
; if mod == gHC_PRIM
- then returnM (Succeeded (ghcPrimIface,
+ then return (Succeeded (ghcPrimIface,
"<built in interface for GHC.Prim>"))
else do
-- Look for the file
; hsc_env <- getTopEnv
- ; mb_found <- ioToIOEnv (findExactModule hsc_env mod)
+ ; mb_found <- liftIO (findExactModule hsc_env mod)
; case mb_found of {
err | notFound err -> do
{ traceIf (ptext SLIT("...not found"))
; dflags <- getDOpts
- ; returnM (Failed (cannotFindInterface dflags
+ ; return (Failed (cannotFindInterface dflags
(moduleName mod) err)) } ;
Found loc mod -> do
; if thisPackage dflags == modulePackageId mod
&& not (isOneShot (ghcMode dflags))
- then returnM (Failed (homeModError mod loc))
+ then return (Failed (homeModError mod loc))
else do {
; traceIf (ptext SLIT("readIFace") <+> text file_path)
; read_result <- readIface mod file_path hi_boot_file
; case read_result of
- Failed err -> returnM (Failed (badIfaceFile file_path err))
+ Failed err -> return (Failed (badIfaceFile file_path err))
Succeeded iface
| mi_module iface /= mod ->
return (Failed (wrongIfaceModErr iface mod file_path))
| otherwise ->
- returnM (Succeeded (iface, file_path))
+ return (Succeeded (iface, file_path))
-- Don't forget to fill in the package name...
}}}}
projects / ghc-hetmet.git / blobdiff