-- Template Haskell stuff
checkWellStaged, spliceOK, bracketOK, tcMetaTy, thLevel,
- topIdLvl,
+ topIdLvl, thTopLevelId,
-- New Ids
newLocalName, newDFunName, newFamInstTyConName,
tcMetaTy tc_name
= tcLookupTyCon tc_name `thenM` \ t ->
returnM (mkTyConApp t [])
+
+thTopLevelId :: Id -> Bool
+-- See Note [What is a top-level Id?] in TcSplice
+thTopLevelId id = isGlobalId id || isExternalName (idName id)
\end{code}
--------------------------------------
thBrackId orig id ps_var lie_var
- | isExternalName id_name
+ | thTopLevelId id
= -- Top-level identifiers in this module,
-- (which have External Names)
-- are just like the imported case:
-- But we do need to put f into the keep-alive
-- set, because after desugaring the code will
-- only mention f's *name*, not f itself.
- do { keepAliveTc id_name; return id }
+ do { keepAliveTc id; return id }
| otherwise
= -- Nested identifiers, such as 'x' in
-- Update the pending splices
; ps <- readMutVar ps_var
- ; writeMutVar ps_var ((id_name, nlHsApp (nlHsVar lift) (nlHsVar id)) : ps)
+ ; writeMutVar ps_var ((idName id, nlHsApp (nlHsVar lift) (nlHsVar id)) : ps)
; return id } }
- where
- id_name = idName id
#endif /* GHCI */
\end{code}
mappM bad_unboxed (filter (isUnLiftedType . idType) zonked_ids) ;
traceTc (text "tcs 1") ;
- let { -- (a) Make all the bound ids "global" ids, now that
- -- they're notionally top-level bindings. This is
- -- important: otherwise when we come to compile an expression
- -- using these ids later, the byte code generator will consider
- -- the occurrences to be free rather than global.
- --
- -- (b) Tidy their types; this is important, because :info may
- -- ask to look at them, and :info expects the things it looks
- -- up to have tidy types
- global_ids = map globaliseAndTidy zonked_ids ;
+ let { global_ids = map globaliseAndTidy zonked_ids } ;
{- ---------------------------------------------
At one stage I removed any shadowed bindings from the type_env;
Hence this code is commented out
-------------------------------------------------- -}
- } ;
dumpOptTcRn Opt_D_dump_tc
(vcat [text "Bound Ids" <+> pprWithCommas ppr global_ids,
nest 2 (ppr id <+> dcolon <+> ppr (idType id))])
globaliseAndTidy :: Id -> Id
-globaliseAndTidy id
--- Give the Id a Global Name, and tidy its type
+globaliseAndTidy id -- Note [Interactively-bound Ids in GHCi]
= Id.setIdType (globaliseId VanillaGlobal id) tidy_type
where
tidy_type = tidyTopType (idType id)
\end{code}
+Note [Interactively-bound Ids in GHCi]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The Ids bound by previous Stmts in Template Haskell are currently
+ a) GlobalIds
+ b) with an Internal Name (not External)
+ c) and a tidied type
+
+ (a) They must be GlobalIds (not LocalIds) otherwise when we come to
+ compile an expression using these ids later, the byte code
+ generator will consider the occurrences to be free rather than
+ global.
+
+ (b) They retain their Internal names becuase we don't have a suitable
+ Module to name them with. We could revisit this choice.
+
+ (c) Their types are tidied. This is important, because :info may ask
+ to look at them, and :info expects the things it looks up to have
+ tidy types
+
+
+--------------------------------------------------------------------------
+ Typechecking Stmts in GHCi
+
Here is the grand plan, implemented in tcUserStmt
What you type The IO [HValue] that hscStmt returns
recordThUse :: TcM ()
recordThUse = do { env <- getGblEnv; writeMutVar (tcg_th_used env) True }
-keepAliveTc :: Name -> TcM () -- Record the name in the keep-alive set
-keepAliveTc n = do { env <- getGblEnv;
- ; updMutVar (tcg_keep env) (`addOneToNameSet` n) }
+keepAliveTc :: Id -> TcM () -- Record the name in the keep-alive set
+keepAliveTc id
+ | isLocalId id = do { env <- getGblEnv;
+ ; updMutVar (tcg_keep env) (`addOneToNameSet` idName id) }
+ | otherwise = return ()
keepAliveSetTc :: NameSet -> TcM () -- Record the name in the keep-alive set
keepAliveSetTc ns = do { env <- getGblEnv;
-- Incremented when going inside a bracket,
-- decremented when going inside a splice
-- NB: ThLevel is one greater than the 'n' in Fig 2 of the
- -- original "Template meta-programmign for Haskell" paper
+ -- original "Template meta-programming for Haskell" paper
impLevel, topLevel :: ThLevel
topLevel = 1 -- Things defined at top level of this module
Note [Template Haskell levels]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Imported things are impLevel (= 0)
+
+* In GHCi, variables bound by a previous command are treated
+ as impLevel, because we have bytecode for them.
+
* Variables are bound at the "current level"
+
* The current level starts off at topLevel (= 1)
+
* The level is decremented by splicing $(..)
incremented by brackets [| |]
incremented by name-quoting 'f
- Non-top-level Only if there is a liftable instance
h = \(x:Int) -> [| x |]
+See Note [What is a top-level Id?]
+
Note [Quoting names]
~~~~~~~~~~~~~~~~~~~~
-A quoted name is a bit like a quoted expression, except that we have no
-cross-stage lifting (c.f. TcExpr.thBrackId).
+A quoted name 'n is a bit like a quoted expression [| n |], except that we
+have no cross-stage lifting (c.f. TcExpr.thBrackId). So, after incrementing
+the use-level to account for the brackets, the cases are:
-Examples:
+ bind > use Error
+ bind = use OK
+ bind < use
+ Imported things OK
+ Top-level things OK
+ Non-top-level Error
+
+See Note [What is a top-level Id?] in TcEnv. Examples:
f 'map -- OK; also for top-level defns of this module
[| \x. $(f 'x) |] -- OK
+Note [What is a top-level Id?]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+In the level-control criteria above, we need to know what a "top level Id" is.
+There are three kinds:
+ * Imported from another module (GlobalId, ExternalName)
+ * Bound at the top level of this module (ExternalName)
+ * In GHCi, bound by a previous stmt (GlobalId)
+It's strange that there is no one criterion tht picks out all three, but that's
+how it is right now. (The obvious thing is to give an ExternalName to GHCi Ids
+bound in an earlier Stmt, but what module would you choose? See
+Note [Interactively-bound Ids in GHCi] in TcRnDriver.)
+
+The predicate we use is TcEnv.thTopLevelId.
+
%************************************************************************
%* *
getLIEVar `thenM` \ lie_var ->
setStage (Brack next_level pending_splices lie_var) (
- getLIE (tc_bracket brack)
+ getLIE (tc_bracket next_level brack)
) `thenM` \ (meta_ty, lie) ->
tcSimplifyBracket lie `thenM_`
returnM (noLoc (HsBracketOut brack pendings))
}
-tc_bracket :: HsBracket Name -> TcM TcType
-tc_bracket (VarBr name) -- Note [Quoting names]
+tc_bracket :: ThLevel -> HsBracket Name -> TcM TcType
+tc_bracket use_lvl (VarBr name) -- Note [Quoting names]
= do { thing <- tcLookup name
; case thing of
AGlobal _ -> return ()
- ATcId { tct_level = bind_lvl }
- | isExternalName name -- C.f isExternalName case of
- -> keepAliveTc name -- TcExpr.thBrackId
+ ATcId { tct_level = bind_lvl, tct_id = id }
+ | thTopLevelId id -- C.f thTopLevelId case of
+ -> keepAliveTc id -- TcExpr.thBrackId
| otherwise
- -> do { use_stage <- getStage
- ; checkTc (thLevel use_stage == bind_lvl)
+ -> do { checkTc (use_lvl == bind_lvl)
(quotedNameStageErr name) }
other -> pprPanic "th_bracket" (ppr name)
; tcMetaTy nameTyConName -- Result type is Var (not Q-monadic)
}
-tc_bracket (ExpBr expr)
+tc_bracket use_lvl (ExpBr expr)
= do { any_ty <- newFlexiTyVarTy liftedTypeKind
; tcMonoExpr expr any_ty
; tcMetaTy expQTyConName }
-- Result type is Expr (= Q Exp)
-tc_bracket (TypBr typ)
+tc_bracket use_lvl (TypBr typ)
= do { tcHsSigType ExprSigCtxt typ
; tcMetaTy typeQTyConName }
-- Result type is Type (= Q Typ)
-tc_bracket (DecBr decls)
+tc_bracket use_lvl (DecBr decls)
= do { tcTopSrcDecls emptyModDetails decls
-- Typecheck the declarations, dicarding the result
-- We'll get all that stuff later, when we splice it in
-- Result type is Q [Dec]
}
-tc_bracket (PatBr _)
+tc_bracket use_lvl (PatBr _)
= failWithTc (ptext SLIT("Tempate Haskell pattern brackets are not supported yet"))
quotedNameStageErr v
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