-type TcId = Id -- Type may be a TcType
-type TcIdSet = IdSet
-
-tcLookupDataCon :: Name -> TcM s (DataCon, [TcType], TcType)
-tcLookupDataCon con_name
- = tcLookupValue con_name `thenNF_Tc` \ con_id ->
- case isDataConWrapId_maybe con_id of {
- Nothing -> failWithTc (badCon con_id);
- Just data_con ->
-
- tcInstId con_id `thenNF_Tc` \ (_, _, con_tau) ->
- -- Ignore the con_theta; overloaded constructors only
- -- behave differently when called, not when used for
- -- matching.
- let
- (arg_tys, result_ty) = splitFunTys con_tau
- in
- ASSERT( maybeToBool (splitAlgTyConApp_maybe result_ty) )
- returnTc (data_con, arg_tys, result_ty) }
-
--- A useful function that takes an occurrence of a global thing
--- and instantiates its type with fresh type variables
-tcInstId :: Id
- -> NF_TcM s ([TcTyVar], -- It's instantiated type
- TcThetaType, --
- TcType) --
-tcInstId id
- = let
- (tyvars, rho) = splitForAllTys (unannotTy (idType id))
- in
- tcInstTyVars tyvars `thenNF_Tc` \ (tyvars', arg_tys, tenv) ->
- let
- rho' = substTy tenv rho
- (theta', tau') = splitRhoTy rho'
- in
- returnNF_Tc (tyvars', theta', tau')
+instance Outputable Stage where
+ ppr Comp = text "Comp"
+ ppr (Brack l _ _) = text "Brack" <+> int l
+ ppr (Splice l) = text "Splice" <+> int l
+
+
+metaLevel :: Stage -> Level
+metaLevel Comp = topLevel
+metaLevel (Splice l) = l
+metaLevel (Brack l _ _) = l
+
+
+checkWellStaged :: SDoc -- What the stage check is for
+ -> Level -- Binding level
+ -> Stage -- Use stage
+ -> TcM () -- Fail if badly staged, adding an error
+checkWellStaged pp_thing bind_lvl use_stage
+ | bind_lvl <= use_lvl -- OK!
+ = returnM ()
+
+ | bind_lvl == topLevel -- GHC restriction on top level splices
+ = failWithTc $
+ sep [ptext SLIT("GHC stage restriction:") <+> pp_thing,
+ nest 2 (ptext SLIT("is used in a top-level splice, and must be imported, not defined locally"))]
+
+ | otherwise -- Badly staged
+ = failWithTc $
+ ptext SLIT("Stage error:") <+> pp_thing <+>
+ hsep [ptext SLIT("is bound at stage") <+> ppr bind_lvl,
+ ptext SLIT("but used at stage") <+> ppr use_lvl]
+ where
+ use_lvl = metaLevel use_stage
+
+
+topIdLvl :: Id -> Level
+-- Globals may either be imported, or may be from an earlier "chunk"
+-- (separated by declaration splices) of this module. The former
+-- *can* be used inside a top-level splice, but the latter cannot.
+-- Hence we give the former impLevel, but the latter topLevel
+-- E.g. this is bad:
+-- x = [| foo |]
+-- $( f x )
+-- By the time we are prcessing the $(f x), the binding for "x"
+-- will be in the global env, not the local one.
+topIdLvl id | isLocalId id = topLevel
+ | otherwise = impLevel
+
+-- Indicates the legal transitions on bracket( [| |] ).
+bracketOK :: Stage -> Maybe Level
+bracketOK (Brack _ _ _) = Nothing -- Bracket illegal inside a bracket
+bracketOK stage = (Just (metaLevel stage + 1))
+
+-- Indicates the legal transitions on splice($).
+spliceOK :: Stage -> Maybe Level
+spliceOK (Splice _) = Nothing -- Splice illegal inside splice
+spliceOK stage = Just (metaLevel stage - 1)
+
+tcMetaTy :: Name -> TcM Type
+-- Given the name of a Template Haskell data type,
+-- return the type
+-- E.g. given the name "Expr" return the type "Expr"
+tcMetaTy tc_name
+ = tcLookupTyCon tc_name `thenM` \ t ->
+ returnM (mkGenTyConApp t [])
+ -- Use mkGenTyConApp because it might be a synonym