diff options
Diffstat (limited to 'compiler/main/TidyPgm.lhs')
| -rw-r--r-- | compiler/main/TidyPgm.lhs | 66 |
1 files changed, 50 insertions, 16 deletions
diff --git a/compiler/main/TidyPgm.lhs b/compiler/main/TidyPgm.lhs index 34afd5ca0e..01de9af4ee 100644 --- a/compiler/main/TidyPgm.lhs +++ b/compiler/main/TidyPgm.lhs @@ -309,6 +309,9 @@ tidyProgram hsc_env (ModGuts { mg_module = mod ; omit_prags = dopt Opt_OmitInterfacePragmas dflags ; expose_all = dopt Opt_ExposeAllUnfoldings dflags ; th = xopt Opt_TemplateHaskell dflags + ; data_kinds = xopt Opt_DataKinds dflags + ; no_trim_types = th || data_kinds + -- See Note [When we can't trim types] } ; showPass dflags CoreTidy @@ -334,7 +337,7 @@ tidyProgram hsc_env (ModGuts { mg_module = mod ; final_ids = [ id | id <- bindersOfBinds tidy_binds, isExternalName (idName id)] - ; tidy_type_env = tidyTypeEnv omit_prags th export_set + ; tidy_type_env = tidyTypeEnv omit_prags no_trim_types export_set (extendTypeEnvWithIds type_env final_ids) ; tidy_insts = tidyInstances (lookup_dfun tidy_type_env) insts @@ -410,7 +413,7 @@ lookup_dfun type_env dfun_id -------------------------- tidyTypeEnv :: Bool -- Compiling without -O, so omit prags - -> Bool -- Template Haskell is on + -> Bool -- Type-trimming flag -> NameSet -> TypeEnv -> TypeEnv -- The competed type environment is gotten from @@ -423,11 +426,11 @@ tidyTypeEnv :: Bool -- Compiling without -O, so omit prags -- This truncates the type environment to include only the -- exported Ids and things needed from them, which saves space -tidyTypeEnv omit_prags th exports type_env +tidyTypeEnv omit_prags no_trim_types exports type_env = let type_env1 = filterNameEnv (not . isWiredInName . getName) type_env -- (1) remove wired-in things - type_env2 | omit_prags = mapNameEnv (trimThing th exports) type_env1 + type_env2 | omit_prags = mapNameEnv (trimThing no_trim_types exports) type_env1 | otherwise = type_env1 -- (2) trimmed if necessary in @@ -436,9 +439,9 @@ tidyTypeEnv omit_prags th exports type_env -------------------------- trimThing :: Bool -> NameSet -> TyThing -> TyThing -- Trim off inessentials, for boot files and no -O -trimThing th exports (ATyCon tc) - | not th && not (mustExposeTyCon exports tc) - = ATyCon (makeTyConAbstract tc) -- Note [Trimming and Template Haskell] +trimThing no_trim_types exports (ATyCon tc) + | not (mustExposeTyCon no_trim_types exports tc) + = ATyCon (makeTyConAbstract tc) -- Note [When we can't trim types] trimThing _th _exports (AnId id) | not (isImplicitId id) @@ -448,30 +451,61 @@ trimThing _th _exports other_thing = other_thing -{- Note [Trimming and Template Haskell] - ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Consider (Trac #2386) this +{- Note [When we can't trim types] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The basic idea of type trimming is to export algebraic data types +abstractly (without their data constructors) when compiling without +-O, unless of course they are explicitly exported by the user. + +We always export synonyms, because they can be mentioned in the type +of an exported Id. We could do a full dependency analysis starting +from the explicit exports, but that's quite painful, and not done for +now. + +But there are some times we can't do that, indicated by the 'no_trim_types' flag. + +First, Template Haskell. Consider (Trac #2386) this module M(T, makeOne) where data T = Yay String makeOne = [| Yay "Yep" |] Notice that T is exported abstractly, but makeOne effectively exports it too! A module that splices in $(makeOne) will then look for a declartion of Yay, so it'd better be there. Hence, brutally but simply, we switch off type -constructor trimming if TH is enabled in this module. -} - - -mustExposeTyCon :: NameSet -- Exports +constructor trimming if TH is enabled in this module. + +Second, data kinds. Consider (Trac #5912) + {-# LANGUAGE DataKinds #-} + module M() where + data UnaryTypeC a = UnaryDataC a + type Bug = 'UnaryDataC +We always export synonyms, so Bug is exposed, and that means that +UnaryTypeC must be too, even though it's not explicitly exported. In +effect, DataKinds means that we'd need to do a full dependency analysis +to see what data constructors are mentioned. But we don't do that yet. + +In these two cases we just switch off type trimming altogether. + -} + +mustExposeTyCon :: Bool -- Type-trimming flag + -> NameSet -- Exports -> TyCon -- The tycon -> Bool -- Can its rep be hidden? -- We are compiling without -O, and thus trying to write as little as -- possible into the interface file. But we must expose the details of -- any data types whose constructors or fields are exported -mustExposeTyCon exports tc - | not (isAlgTyCon tc) -- Synonyms +mustExposeTyCon no_trim_types exports tc + | no_trim_types -- See Note [When we can't trim types] + = True + + | not (isAlgTyCon tc) -- Always expose synonyms (otherwise we'd have to + -- figure out whether it was mentioned in the type + -- of any other exported thing) = True + | isEnumerationTyCon tc -- For an enumeration, exposing the constructors = True -- won't lead to the need for further exposure -- (This includes data types with no constructors.) + | isFamilyTyCon tc -- Open type family = True |