%
% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
TcSplice: Template Haskell splices
\begin{code}
module TcSplice(
tcSpliceExpr, tcTypedBracket, tcUntypedBracket,
runQuasiQuoteExpr, runQuasiQuotePat,
runQuasiQuoteDecl, runQuasiQuoteType,
runAnnotation,
#ifdef GHCI
runMetaE, runMetaP, runMetaT, runMetaD, runQuasi,
tcTopSpliceExpr, lookupThName_maybe,
#endif
) where
#include "HsVersions.h"
import HsSyn
import Annotations
import Name
import TcRnMonad
import RdrName
import TcType
#ifdef GHCI
import HscMain
import HscTypes
import Convert
import RnExpr
import RnEnv
import RnTypes
import TcExpr
import TcHsSyn
import TcSimplify
import TcUnify
import Type
import Kind
import NameSet
import TcEnv
import TcMType
import TcHsType
import TcIface
import TypeRep
import FamInst
import FamInstEnv
import InstEnv
import NameEnv
import PrelNames
import OccName
import Hooks
import Var
import Module
import LoadIface
import Class
import Inst
import TyCon
import CoAxiom
import PatSyn ( patSynName )
import ConLike
import DataCon
import TcEvidence( TcEvBinds(..) )
import Id
import IdInfo
import DsExpr
import DsMonad hiding (Splice)
import Serialized
import ErrUtils
import SrcLoc
import Util
import Data.List ( mapAccumL )
import Unique
import Data.Maybe
import BasicTypes hiding( SuccessFlag(..) )
import Maybes( MaybeErr(..) )
import DynFlags
import Panic
import FastString
import Outputable
import Control.Monad ( when )
import DsMeta
import qualified Language.Haskell.TH as TH
import qualified Language.Haskell.TH.Syntax as TH
import GHC.Desugar ( AnnotationWrapper(..) )
import qualified Data.Map as Map
import Data.Dynamic ( fromDynamic, toDyn )
import Data.Typeable ( typeOf )
import Data.Data (Data)
import GHC.Exts ( unsafeCoerce# )
#endif
\end{code}
%************************************************************************
%* *
\subsection{Main interface + stubs for the non-GHCI case
%* *
%************************************************************************
\begin{code}
tcTypedBracket :: HsBracket Name -> TcRhoType -> TcM (HsExpr TcId)
tcUntypedBracket :: HsBracket Name -> [PendingRnSplice] -> TcRhoType -> TcM (HsExpr TcId)
tcSpliceExpr :: HsSplice Name -> TcRhoType -> TcM (HsExpr TcId)
runQuasiQuoteExpr :: HsQuasiQuote RdrName -> RnM (LHsExpr RdrName)
runQuasiQuotePat :: HsQuasiQuote RdrName -> RnM (LPat RdrName)
runQuasiQuoteType :: HsQuasiQuote RdrName -> RnM (LHsType RdrName)
runQuasiQuoteDecl :: HsQuasiQuote RdrName -> RnM [LHsDecl RdrName]
runAnnotation :: CoreAnnTarget -> LHsExpr Name -> TcM Annotation
#ifndef GHCI
tcTypedBracket x _ = failTH x "Template Haskell bracket"
tcUntypedBracket x _ _ = failTH x "Template Haskell bracket"
tcSpliceExpr e _ = failTH e "Template Haskell splice"
runQuasiQuoteExpr q = failTH q "quasiquote"
runQuasiQuotePat q = failTH q "pattern quasiquote"
runQuasiQuoteType q = failTH q "type quasiquote"
runQuasiQuoteDecl q = failTH q "declaration quasiquote"
runAnnotation _ q = failTH q "annotation"
#else
\end{code}
Note [How top-level splices are handled]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Top-level splices (those not inside a [| .. |] quotation bracket) are handled
very straightforwardly:
1. tcTopSpliceExpr: typecheck the body e of the splice $(e)
2. runMetaT: desugar, compile, run it, and convert result back to
HsSyn RdrName (of the appropriate flavour, eg HsType RdrName,
HsExpr RdrName etc)
3. treat the result as if that's what you saw in the first place
e.g for HsType, rename and kind-check
for HsExpr, rename and type-check
(The last step is different for decls, because they can *only* be
top-level: we return the result of step 2.)
Note [How brackets and nested splices are handled]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Nested splices (those inside a [| .. |] quotation bracket),
are treated quite differently.
Remember, there are two forms of bracket
typed [|| e ||]
and untyped [| e |]
The life cycle of a typed bracket:
* Starts as HsBracket
* When renaming:
* Set the ThStage to (Brack s RnPendingTyped)
* Rename the body
* Result is still a HsBracket
* When typechecking:
* Set the ThStage to (Brack s (TcPending ps_var lie_var))
* Typecheck the body, and throw away the elaborated result
* Nested splices (which must be typed) are typechecked, and
the results accumulated in ps_var; their constraints
accumulate in lie_var
* Result is a HsTcBracketOut rn_brack pending_splices
where rn_brack is the incoming renamed bracket
The life cycle of a un-typed bracket:
* Starts as HsBracket
* When renaming:
* Set the ThStage to (Brack s (RnPendingUntyped ps_var))
* Rename the body
* Nested splices (which must be untyped) are renamed, and the
results accumulated in ps_var
* Result is still (HsRnBracketOut rn_body pending_splices)
* When typechecking a HsRnBracketOut
* Typecheck the pending_splices individually
* Ignore the body of the bracket; just check that the context
expects a bracket of that type (e.g. a [p| pat |] bracket should
be in a context needing a (Q Pat)
* Result is a HsTcBracketOut rn_brack pending_splices
where rn_brack is the incoming renamed bracket
In both cases, desugaring happens like this:
* HsTcBracketOut is desugared by DsMeta.dsBracket. It
a) Extends the ds_meta environment with the PendingSplices
attached to the bracket
b) Converts the quoted (HsExpr Name) to a CoreExpr that, when
run, will produce a suitable TH expression/type/decl. This
is why we leave the *renamed* expression attached to the bracket:
the quoted expression should not be decorated with all the goop
added by the type checker
* Each splice carries a unique Name, called a "splice point", thus
${n}(e). The name is initialised to an (Unqual "splice") when the
splice is created; the renamer gives it a unique.
* When DsMeta (used to desugar the body of the bracket) comes across
a splice, it looks up the splice's Name, n, in the ds_meta envt,
to find an (HsExpr Id) that should be substituted for the splice;
it just desugars it to get a CoreExpr (DsMeta.repSplice).
Example:
Source: f = [| Just $(g 3) |]
The [| |] part is a HsBracket
Typechecked: f = [| Just ${s7}(g 3) |]{s7 = g Int 3}
The [| |] part is a HsBracketOut, containing *renamed*
(not typechecked) expression
The "s7" is the "splice point"; the (g Int 3) part
is a typechecked expression
Desugared: f = do { s7 <- g Int 3
; return (ConE "Data.Maybe.Just" s7) }
Note [Template Haskell state diagram]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Here are the ThStages, s, their corresponding level numbers
(the result of (thLevel s)), and their state transitions.
----------- $ ------------ $
| Comp | ---------> | Splice | -----|
| 1 | | 0 | <----|
----------- ------------
^ | ^ |
$ | | [||] $ | | [||]
| v | v
-------------- ----------------
| Brack Comp | | Brack Splice |
| 2 | | 1 |
-------------- ----------------
* Normal top-level declarations start in state Comp
(which has level 1).
Annotations start in state Splice, since they are
treated very like a splice (only without a '$')
* Code compiled in state Splice (and only such code)
will be *run at compile time*, with the result replacing
the splice
* The original paper used level -1 instead of 0, etc.
* The original paper did not allow a splice within a
splice, but there is no reason not to. This is the
$ transition in the top right.
Note [Template Haskell levels]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Imported things are impLevel (= 0)
* However things at level 0 are not *necessarily* imported.
eg $( \b -> ... ) here b is bound at level 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 outerLevel (= 1)
* The level is decremented by splicing $(..)
incremented by brackets [| |]
incremented by name-quoting 'f
When a variable is used, we compare
bind: binding level, and
use: current level at usage site
Generally
bind > use Always error (bound later than used)
[| \x -> $(f x) |]
bind = use Always OK (bound same stage as used)
[| \x -> $(f [| x |]) |]
bind < use Inside brackets, it depends
Inside splice, OK
Inside neither, OK
For (bind < use) inside brackets, there are three cases:
- Imported things OK f = [| map |]
- Top-level things OK g = [| f |]
- Non-top-level Only if there is a liftable instance
h = \(x:Int) -> [| x |]
To track top-level-ness we use the ThBindEnv in TcLclEnv
For example:
f = ...
g1 = $(map ...) is OK
g2 = $(f ...) is not OK; because we havn't compiled f yet
%************************************************************************
%* *
\subsection{Quoting an expression}
%* *
%************************************************************************
\begin{code}
tcTypedBracket brack@(TExpBr expr) res_ty
= addErrCtxt (quotationCtxtDoc brack) $
do { cur_stage <- getStage
; ps_ref <- newMutVar []
; lie_var <- getConstraintVar
; (_tc_expr, expr_ty) <- setStage (Brack cur_stage (TcPending ps_ref lie_var)) $
tcInferRhoNC expr
; meta_ty <- tcTExpTy expr_ty
; co <- unifyType meta_ty res_ty
; ps' <- readMutVar ps_ref
; texpco <- tcLookupId unsafeTExpCoerceName
; return (mkHsWrapCo co (unLoc (mkHsApp (nlHsTyApp texpco [expr_ty])
(noLoc (HsTcBracketOut brack ps'))))) }
tcTypedBracket other_brack _
= pprPanic "tcTypedBracket" (ppr other_brack)
tcUntypedBracket brack ps res_ty
= do { traceTc "tc_bracket untyped" (ppr brack $$ ppr ps)
; ps' <- mapM tcPendingSplice ps
; meta_ty <- tcBrackTy brack
; co <- unifyType meta_ty res_ty
; traceTc "tc_bracket done untyped" (ppr meta_ty)
; return (mkHsWrapCo co (HsTcBracketOut brack ps')) }
tcBrackTy :: HsBracket Name -> TcM TcType
tcBrackTy (VarBr _ _) = tcMetaTy nameTyConName
tcBrackTy (ExpBr _) = tcMetaTy expQTyConName
tcBrackTy (TypBr _) = tcMetaTy typeQTyConName
tcBrackTy (DecBrG _) = tcMetaTy decsQTyConName
tcBrackTy (PatBr _) = tcMetaTy patQTyConName
tcBrackTy (DecBrL _) = panic "tcBrackTy: Unexpected DecBrL"
tcBrackTy (TExpBr _) = panic "tcUntypedBracket: Unexpected TExpBr"
tcPendingSplice :: PendingRnSplice -> TcM PendingTcSplice
tcPendingSplice (PendingRnExpSplice (HsSplice n expr))
= do { res_ty <- tcMetaTy expQTyConName
; tc_pending_splice n expr res_ty }
tcPendingSplice (PendingRnPatSplice (HsSplice n expr))
= do { res_ty <- tcMetaTy patQTyConName
; tc_pending_splice n expr res_ty }
tcPendingSplice (PendingRnTypeSplice (HsSplice n expr))
= do { res_ty <- tcMetaTy typeQTyConName
; tc_pending_splice n expr res_ty }
tcPendingSplice (PendingRnDeclSplice (HsSplice n expr))
= do { res_ty <- tcMetaTy decsQTyConName
; tc_pending_splice n expr res_ty }
tcPendingSplice (PendingRnCrossStageSplice n)
= do { res_ty <- tcMetaTy expQTyConName
; tc_pending_splice n (nlHsApp (nlHsVar liftName) (nlHsVar n)) res_ty }
tc_pending_splice :: Name -> LHsExpr Name -> TcRhoType -> TcM PendingTcSplice
tc_pending_splice splice_name expr res_ty
= do { expr' <- tcMonoExpr expr res_ty
; return (splice_name, expr') }
tcTExpTy :: TcType -> TcM TcType
tcTExpTy tau = do
q <- tcLookupTyCon qTyConName
texp <- tcLookupTyCon tExpTyConName
return (mkTyConApp q [mkTyConApp texp [tau]])
\end{code}
%************************************************************************
%* *
\subsection{Splicing an expression}
%* *
%************************************************************************
\begin{code}
tcSpliceExpr splice@(HsSplice name expr) res_ty
= addErrCtxt (spliceCtxtDoc splice) $
setSrcSpan (getLoc expr) $ do
{ stage <- getStage
; case stage of
Splice {} -> tcTopSplice expr res_ty
Comp -> tcTopSplice expr res_ty
Brack pop_stage pend -> tcNestedSplice pop_stage pend name expr res_ty }
tcNestedSplice :: ThStage -> PendingStuff -> Name
-> LHsExpr Name -> TcRhoType -> TcM (HsExpr Id)
tcNestedSplice pop_stage (TcPending ps_var lie_var) splice_name expr res_ty
= do { meta_exp_ty <- tcTExpTy res_ty
; expr' <- setStage pop_stage $
setConstraintVar lie_var $
tcMonoExpr expr meta_exp_ty
; untypeq <- tcLookupId unTypeQName
; let expr'' = mkHsApp (nlHsTyApp untypeq [res_ty]) expr'
; ps <- readMutVar ps_var
; writeMutVar ps_var ((splice_name, expr'') : ps)
; return (panic "tcSpliceExpr") }
tcNestedSplice _ _ splice_name _ _
= pprPanic "tcNestedSplice: rename stage found" (ppr splice_name)
tcTopSplice :: LHsExpr Name -> TcRhoType -> TcM (HsExpr Id)
tcTopSplice expr res_ty
= do {
meta_exp_ty <- tcTExpTy res_ty
; zonked_q_expr <- tcTopSpliceExpr True $
tcMonoExpr expr meta_exp_ty
; expr2 <- runMetaE zonked_q_expr
; showSplice "expression" expr (ppr expr2)
; addErrCtxt (spliceResultDoc expr) $ do
{ (exp3, _fvs) <- rnLExpr expr2
; exp4 <- tcMonoExpr exp3 res_ty
; return (unLoc exp4) } }
\end{code}
%************************************************************************
%* *
\subsection{Error messages}
%* *
%************************************************************************
\begin{code}
quotationCtxtDoc :: HsBracket Name -> SDoc
quotationCtxtDoc br_body
= hang (ptext (sLit "In the Template Haskell quotation"))
2 (ppr br_body)
spliceCtxtDoc :: HsSplice Name -> SDoc
spliceCtxtDoc splice
= hang (ptext (sLit "In the Template Haskell splice"))
2 (pprTypedSplice splice)
spliceResultDoc :: LHsExpr Name -> SDoc
spliceResultDoc expr
= sep [ ptext (sLit "In the result of the splice:")
, nest 2 (char '$' <> pprParendExpr expr)
, ptext (sLit "To see what the splice expanded to, use -ddump-splices")]
tcTopSpliceExpr :: Bool -> TcM (LHsExpr Id) -> TcM (LHsExpr Id)
tcTopSpliceExpr isTypedSplice tc_action
= checkNoErrs $
unsetGOptM Opt_DeferTypeErrors $
setStage (Splice isTypedSplice) $
do {
(expr', lie) <- captureConstraints tc_action
; const_binds <- simplifyTop lie
; zonkTopLExpr (mkHsDictLet (EvBinds const_binds) expr') }
\end{code}
Note [Renamer errors]
~~~~~~~~~~~~~~~~~~~~~
It's important to wrap renamer calls in checkNoErrs, because the
renamer does not fail for out of scope variables etc. Instead it
returns a bogus term/type, so that it can report more than one error.
We don't want the type checker to see these bogus unbound variables.
%************************************************************************
%* *
Annotations
%* *
%************************************************************************
\begin{code}
runAnnotation target expr = do
loc <- getSrcSpanM
data_class <- tcLookupClass dataClassName
to_annotation_wrapper_id <- tcLookupId toAnnotationWrapperName
zonked_wrapped_expr' <- tcTopSpliceExpr False $
do { (expr', expr_ty) <- tcInferRhoNC expr
; wrapper <- instCall AnnOrigin [expr_ty] [mkClassPred data_class [expr_ty]]
; let specialised_to_annotation_wrapper_expr
= L loc (HsWrap wrapper (HsVar to_annotation_wrapper_id))
; return (L loc (HsApp specialised_to_annotation_wrapper_expr expr')) }
flip runMetaAW zonked_wrapped_expr' $ \annotation_wrapper ->
case annotation_wrapper of
AnnotationWrapper value | let serialized = toSerialized serializeWithData value ->
seqSerialized serialized `seq` Annotation {
ann_target = target,
ann_value = serialized
}
\end{code}
%************************************************************************
%* *
Quasi-quoting
%* *
%************************************************************************
Note [Quasi-quote overview]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
The GHC "quasi-quote" extension is described by Geoff Mainland's paper
"Why it's nice to be quoted: quasiquoting for Haskell" (Haskell
Workshop 2007).
Briefly, one writes
[p| stuff |]
and the arbitrary string "stuff" gets parsed by the parser 'p', whose
type should be Language.Haskell.TH.Quote.QuasiQuoter. 'p' must be
defined in another module, because we are going to run it here. It's
a bit like a TH splice:
$(p "stuff")
However, you can do this in patterns as well as terms. Because of this,
the splice is run by the *renamer* rather than the type checker.
%************************************************************************
%* *
\subsubsection{Quasiquotation}
%* *
%************************************************************************
See Note [Quasi-quote overview] in TcSplice.
\begin{code}
runQuasiQuote :: Outputable hs_syn
=> HsQuasiQuote RdrName
-> Name
-> Name
-> MetaOps th_syn hs_syn
-> RnM hs_syn
runQuasiQuote (HsQuasiQuote quoter q_span quote) quote_selector meta_ty meta_ops
= do {
let occ_str = occNameString (rdrNameOcc quoter)
; quoter <- ASSERT( not (null occ_str) )
if head occ_str /= '$' then return quoter
else do { addWarn (deprecatedDollar quoter)
; return (mkRdrUnqual (mkVarOcc (tail occ_str))) }
; quoter' <- lookupOccRn quoter
; when (isUnboundName quoter') failM
; this_mod <- getModule
; let is_local = nameIsLocalOrFrom this_mod quoter'
; checkTc (not is_local) (quoteStageError quoter')
; traceTc "runQQ" (ppr quoter <+> ppr is_local)
; HsQuasiQuote quoter'' _ quote' <- getHooked runQuasiQuoteHook return >>=
($ HsQuasiQuote quoter' q_span quote)
; let quoterExpr = L q_span $! HsVar $! quoter''
; let quoteExpr = L q_span $! HsLit $! HsString quote'
; let expr = L q_span $
HsApp (L q_span $
HsApp (L q_span (HsVar quote_selector)) quoterExpr) quoteExpr
; meta_exp_ty <- tcMetaTy meta_ty
; zonked_q_expr <- tcTopSpliceExpr False (tcMonoExpr expr meta_exp_ty)
; result <- runMetaQ meta_ops zonked_q_expr
; showSplice (mt_desc meta_ops) quoteExpr (ppr result)
; return result }
runQuasiQuoteExpr qq = runQuasiQuote qq quoteExpName expQTyConName exprMetaOps
runQuasiQuotePat qq = runQuasiQuote qq quotePatName patQTyConName patMetaOps
runQuasiQuoteType qq = runQuasiQuote qq quoteTypeName typeQTyConName typeMetaOps
runQuasiQuoteDecl qq = runQuasiQuote qq quoteDecName decsQTyConName declMetaOps
quoteStageError :: Name -> SDoc
quoteStageError quoter
= sep [ptext (sLit "GHC stage restriction:") <+> ppr quoter,
nest 2 (ptext (sLit "is used in a quasiquote, and must be imported, not defined locally"))]
deprecatedDollar :: RdrName -> SDoc
deprecatedDollar quoter
= hang (ptext (sLit "Deprecated syntax:"))
2 (ptext (sLit "quasiquotes no longer need a dollar sign:")
<+> ppr quoter)
\end{code}
%************************************************************************
%* *
\subsection{Running an expression}
%* *
%************************************************************************
\begin{code}
runQuasi :: TH.Q a -> TcM a
runQuasi act = TH.runQ act
\end{code}
\begin{code}
data MetaOps th_syn hs_syn
= MT { mt_desc :: String
, mt_show :: th_syn -> String
, mt_cvt :: SrcSpan -> th_syn -> Either MsgDoc hs_syn
}
exprMetaOps :: MetaOps TH.Exp (LHsExpr RdrName)
exprMetaOps = MT { mt_desc = "expression", mt_show = TH.pprint, mt_cvt = convertToHsExpr }
patMetaOps :: MetaOps TH.Pat (LPat RdrName)
patMetaOps = MT { mt_desc = "pattern", mt_show = TH.pprint, mt_cvt = convertToPat }
typeMetaOps :: MetaOps TH.Type (LHsType RdrName)
typeMetaOps = MT { mt_desc = "type", mt_show = TH.pprint, mt_cvt = convertToHsType }
declMetaOps :: MetaOps [TH.Dec] [LHsDecl RdrName]
declMetaOps = MT { mt_desc = "declarations", mt_show = TH.pprint, mt_cvt = convertToHsDecls }
runMetaAW :: Outputable output
=> (AnnotationWrapper -> output)
-> LHsExpr Id
-> TcM output
runMetaAW k = runMeta False (\_ -> return . Right . k)
runMetaQ :: Outputable hs_syn
=> MetaOps th_syn hs_syn
-> LHsExpr Id
-> TcM hs_syn
runMetaQ (MT { mt_show = show_th, mt_cvt = cvt }) expr
= runMeta True run_and_cvt expr
where
run_and_cvt expr_span hval
= do { th_result <- TH.runQ hval
; traceTc "Got TH result:" (text (show_th th_result))
; return (cvt expr_span th_result) }
runMetaE :: LHsExpr Id
-> TcM (LHsExpr RdrName)
runMetaE = runMetaQ exprMetaOps
runMetaP :: LHsExpr Id
-> TcM (LPat RdrName)
runMetaP = runMetaQ patMetaOps
runMetaT :: LHsExpr Id
-> TcM (LHsType RdrName)
runMetaT = runMetaQ typeMetaOps
runMetaD :: LHsExpr Id
-> TcM [LHsDecl RdrName]
runMetaD = runMetaQ declMetaOps
runMeta :: (Outputable hs_syn)
=> Bool
-> (SrcSpan -> x -> TcM (Either MsgDoc hs_syn))
-> LHsExpr Id
-> TcM hs_syn
runMeta show_code run_and_convert expr
= do { traceTc "About to run" (ppr expr)
; recordThSpliceUse
; failIfErrsM
; ds_expr <- initDsTc (dsLExpr expr)
; hsc_env <- getTopEnv
; src_span <- getSrcSpanM
; traceTc "About to run (desugared)" (ppr ds_expr)
; either_hval <- tryM $ liftIO $
HscMain.hscCompileCoreExpr hsc_env src_span ds_expr
; case either_hval of {
Left exn -> fail_with_exn "compile and link" exn ;
Right hval -> do
{
let expr_span = getLoc expr
; either_tval <- tryAllM $
setSrcSpan expr_span $
do { mb_result <- run_and_convert expr_span (unsafeCoerce# hval)
; case mb_result of
Left err -> failWithTc err
Right result -> do { traceTc "Got HsSyn result:" (ppr result)
; return $! result } }
; case either_tval of
Right v -> return v
Left se -> case fromException se of
Just IOEnvFailure -> failM
_ -> fail_with_exn "run" se
}}}
where
fail_with_exn phase exn = do
exn_msg <- liftIO $ Panic.safeShowException exn
let msg = vcat [text "Exception when trying to" <+> text phase <+> text "compile-time code:",
nest 2 (text exn_msg),
if show_code then text "Code:" <+> ppr expr else empty]
failWithTc msg
\end{code}
Note [Exceptions in TH]
~~~~~~~~~~~~~~~~~~~~~~~
Supppose we have something like this
$( f 4 )
where
f :: Int -> Q [Dec]
f n | n>3 = fail "Too many declarations"
| otherwise = ...
The 'fail' is a user-generated failure, and should be displayed as a
perfectly ordinary compiler error message, not a panic or anything
like that. Here's how it's processed:
* 'fail' is the monad fail. The monad instance for Q in TH.Syntax
effectively transforms (fail s) to
qReport True s >> fail
where 'qReport' comes from the Quasi class and fail from its monad
superclass.
* The TcM monad is an instance of Quasi (see TcSplice), and it implements
(qReport True s) by using addErr to add an error message to the bag of errors.
The 'fail' in TcM raises an IOEnvFailure exception
* So, when running a splice, we catch all exceptions; then for
- an IOEnvFailure exception, we assume the error is already
in the error-bag (above)
- other errors, we add an error to the bag
and then fail
Note [Concealed TH exceptions]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When displaying the error message contained in an exception originated from TH
code, we need to make sure that the error message itself does not contain an
exception. For example, when executing the following splice:
$( error ("foo " ++ error "bar") )
the message for the outer exception is a thunk which will throw the inner
exception when evaluated.
For this reason, we display the message of a TH exception using the
'safeShowException' function, which recursively catches any exception thrown
when showing an error message.
To call runQ in the Tc monad, we need to make TcM an instance of Quasi:
\begin{code}
instance TH.Quasi (IOEnv (Env TcGblEnv TcLclEnv)) where
qNewName s = do { u <- newUnique
; let i = getKey u
; return (TH.mkNameU s i) }
qReport True msg = addErr (text msg)
qReport False msg = addWarn (text msg)
qLocation = do { m <- getModule
; l <- getSrcSpanM
; r <- case l of
UnhelpfulSpan _ -> pprPanic "qLocation: Unhelpful location"
(ppr l)
RealSrcSpan s -> return s
; return (TH.Loc { TH.loc_filename = unpackFS (srcSpanFile r)
, TH.loc_module = moduleNameString (moduleName m)
, TH.loc_package = packageIdString (modulePackageId m)
, TH.loc_start = (srcSpanStartLine r, srcSpanStartCol r)
, TH.loc_end = (srcSpanEndLine r, srcSpanEndCol r) }) }
qLookupName = lookupName
qReify = reify
qReifyInstances = reifyInstances
qReifyRoles = reifyRoles
qReifyAnnotations = reifyAnnotations
qReifyModule = reifyModule
qRecover recover main = do { (msgs, mb_res) <- tryTcErrs main
; case mb_res of
Just val -> do { addMessages msgs
; return val }
Nothing -> recover
}
qRunIO io = liftIO io
qAddDependentFile fp = do
ref <- fmap tcg_dependent_files getGblEnv
dep_files <- readTcRef ref
writeTcRef ref (fp:dep_files)
qAddTopDecls thds = do
l <- getSrcSpanM
let either_hval = convertToHsDecls l thds
ds <- case either_hval of
Left exn -> pprPanic "qAddTopDecls: can't convert top-level declarations" exn
Right ds -> return ds
mapM_ (checkTopDecl . unLoc) ds
th_topdecls_var <- fmap tcg_th_topdecls getGblEnv
updTcRef th_topdecls_var (\topds -> ds ++ topds)
where
checkTopDecl :: HsDecl RdrName -> TcM ()
checkTopDecl (ValD binds)
= mapM_ bindName (collectHsBindBinders binds)
checkTopDecl (SigD _)
= return ()
checkTopDecl (ForD (ForeignImport (L _ name) _ _ _))
= bindName name
checkTopDecl _
= addErr $ text "Only function, value, and foreign import declarations may be added with addTopDecl"
bindName :: RdrName -> TcM ()
bindName (Exact n)
= do { th_topnames_var <- fmap tcg_th_topnames getGblEnv
; updTcRef th_topnames_var (\ns -> addOneToNameSet ns n)
}
bindName name =
addErr $
hang (ptext (sLit "The binder") <+> quotes (ppr name) <+> ptext (sLit "is not a NameU."))
2 (text "Probable cause: you used mkName instead of newName to generate a binding.")
qAddModFinalizer fin = do
th_modfinalizers_var <- fmap tcg_th_modfinalizers getGblEnv
updTcRef th_modfinalizers_var (\fins -> fin:fins)
qGetQ = do
th_state_var <- fmap tcg_th_state getGblEnv
th_state <- readTcRef th_state_var
let x = Map.lookup (typeOf x) th_state >>= fromDynamic
return x
qPutQ x = do
th_state_var <- fmap tcg_th_state getGblEnv
updTcRef th_state_var (\m -> Map.insert (typeOf x) (toDyn x) m)
\end{code}
%************************************************************************
%* *
\subsection{Errors and contexts}
%* *
%************************************************************************
\begin{code}
showSplice :: String -> LHsExpr Name -> SDoc -> TcM ()
showSplice what before after
= do { loc <- getSrcSpanM
; traceSplice (vcat [ppr loc <> colon <+> text "Splicing" <+> text what,
nest 2 (sep [nest 2 (ppr before),
text "======>",
nest 2 after])]) }
\end{code}
%************************************************************************
%* *
Instance Testing
%* *
%************************************************************************
\begin{code}
reifyInstances :: TH.Name -> [TH.Type] -> TcM [TH.Dec]
reifyInstances th_nm th_tys
= addErrCtxt (ptext (sLit "In the argument of reifyInstances:")
<+> ppr_th th_nm <+> sep (map ppr_th th_tys)) $
do { loc <- getSrcSpanM
; rdr_ty <- cvt loc (mkThAppTs (TH.ConT th_nm) th_tys)
; (rn_ty, _fvs) <- checkNoErrs $ rnLHsType doc rdr_ty
; (ty, _kind) <- tcLHsType rn_ty
; ty <- zonkTcTypeToType emptyZonkEnv ty
; traceTc "reifyInstances" (ppr ty $$ ppr (typeKind ty))
; case splitTyConApp_maybe ty of
Just (tc, tys)
| Just cls <- tyConClass_maybe tc
-> do { inst_envs <- tcGetInstEnvs
; let (matches, unifies, _) = lookupInstEnv inst_envs cls tys
; traceTc "reifyInstances1" (ppr matches)
; mapM reifyClassInstance (map fst matches ++ unifies) }
| isOpenFamilyTyCon tc
-> do { inst_envs <- tcGetFamInstEnvs
; let matches = lookupFamInstEnv inst_envs tc tys
; traceTc "reifyInstances2" (ppr matches)
; mapM (reifyFamilyInstance . fim_instance) matches }
_ -> bale_out (hang (ptext (sLit "reifyInstances:") <+> quotes (ppr ty))
2 (ptext (sLit "is not a class constraint or type family application"))) }
where
doc = ClassInstanceCtx
bale_out msg = failWithTc msg
cvt :: SrcSpan -> TH.Type -> TcM (LHsType RdrName)
cvt loc th_ty = case convertToHsType loc th_ty of
Left msg -> failWithTc msg
Right ty -> return ty
\end{code}
%************************************************************************
%* *
Reification
%* *
%************************************************************************
\begin{code}
lookupName :: Bool
-> String -> TcM (Maybe TH.Name)
lookupName is_type_name s
= do { lcl_env <- getLocalRdrEnv
; case lookupLocalRdrEnv lcl_env rdr_name of
Just n -> return (Just (reifyName n))
Nothing -> do { mb_nm <- lookupGlobalOccRn_maybe rdr_name
; return (fmap reifyName mb_nm) } }
where
th_name = TH.mkName s
occ_fs :: FastString
occ_fs = mkFastString (TH.nameBase th_name)
occ :: OccName
occ | is_type_name
= if isLexCon occ_fs then mkTcOccFS occ_fs
else mkTyVarOccFS occ_fs
| otherwise
= if isLexCon occ_fs then mkDataOccFS occ_fs
else mkVarOccFS occ_fs
rdr_name = case TH.nameModule th_name of
Nothing -> mkRdrUnqual occ
Just mod -> mkRdrQual (mkModuleName mod) occ
getThing :: TH.Name -> TcM TcTyThing
getThing th_name
= do { name <- lookupThName th_name
; traceIf (text "reify" <+> text (show th_name) <+> brackets (ppr_ns th_name) <+> ppr name)
; tcLookupTh name }
where
ppr_ns (TH.Name _ (TH.NameG TH.DataName _pkg _mod)) = text "data"
ppr_ns (TH.Name _ (TH.NameG TH.TcClsName _pkg _mod)) = text "tc"
ppr_ns (TH.Name _ (TH.NameG TH.VarName _pkg _mod)) = text "var"
ppr_ns _ = panic "reify/ppr_ns"
reify :: TH.Name -> TcM TH.Info
reify th_name
= do { thing <- getThing th_name
; reifyThing thing }
lookupThName :: TH.Name -> TcM Name
lookupThName th_name = do
mb_name <- lookupThName_maybe th_name
case mb_name of
Nothing -> failWithTc (notInScope th_name)
Just name -> return name
lookupThName_maybe :: TH.Name -> TcM (Maybe Name)
lookupThName_maybe th_name
= do { names <- mapMaybeM lookup (thRdrNameGuesses th_name)
; return (listToMaybe names) }
where
lookup rdr_name
= do {
; rdr_env <- getLocalRdrEnv
; case lookupLocalRdrEnv rdr_env rdr_name of
Just name -> return (Just name)
Nothing -> lookupGlobalOccRn_maybe rdr_name }
tcLookupTh :: Name -> TcM TcTyThing
tcLookupTh name
= do { (gbl_env, lcl_env) <- getEnvs
; case lookupNameEnv (tcl_env lcl_env) name of {
Just thing -> return thing;
Nothing ->
case lookupNameEnv (tcg_type_env gbl_env) name of {
Just thing -> return (AGlobal thing);
Nothing ->
if nameIsLocalOrFrom (tcg_mod gbl_env) name
then
failWithTc (notInEnv name)
else
do { mb_thing <- tcLookupImported_maybe name
; case mb_thing of
Succeeded thing -> return (AGlobal thing)
Failed msg -> failWithTc msg
}}}}
notInScope :: TH.Name -> SDoc
notInScope th_name = quotes (text (TH.pprint th_name)) <+>
ptext (sLit "is not in scope at a reify")
notInEnv :: Name -> SDoc
notInEnv name = quotes (ppr name) <+>
ptext (sLit "is not in the type environment at a reify")
reifyRoles :: TH.Name -> TcM [TH.Role]
reifyRoles th_name
= do { thing <- getThing th_name
; case thing of
AGlobal (ATyCon tc) -> return (map reify_role (tyConRoles tc))
_ -> failWithTc (ptext (sLit "No roles associated with") <+> (ppr thing))
}
where
reify_role Nominal = TH.NominalR
reify_role Representational = TH.RepresentationalR
reify_role Phantom = TH.PhantomR
reifyThing :: TcTyThing -> TcM TH.Info
reifyThing (AGlobal (AnId id))
= do { ty <- reifyType (idType id)
; fix <- reifyFixity (idName id)
; let v = reifyName id
; case idDetails id of
ClassOpId cls -> return (TH.ClassOpI v ty (reifyName cls) fix)
_ -> return (TH.VarI v ty Nothing fix)
}
reifyThing (AGlobal (ATyCon tc)) = reifyTyCon tc
reifyThing (AGlobal (AConLike (RealDataCon dc)))
= do { let name = dataConName dc
; ty <- reifyType (idType (dataConWrapId dc))
; fix <- reifyFixity name
; return (TH.DataConI (reifyName name) ty
(reifyName (dataConOrigTyCon dc)) fix)
}
reifyThing (AGlobal (AConLike (PatSynCon ps)))
= noTH (sLit "pattern synonyms") (ppr $ patSynName ps)
reifyThing (ATcId {tct_id = id})
= do { ty1 <- zonkTcType (idType id)
; ty2 <- reifyType ty1
; fix <- reifyFixity (idName id)
; return (TH.VarI (reifyName id) ty2 Nothing fix) }
reifyThing (ATyVar tv tv1)
= do { ty1 <- zonkTcTyVar tv1
; ty2 <- reifyType ty1
; return (TH.TyVarI (reifyName tv) ty2) }
reifyThing thing = pprPanic "reifyThing" (pprTcTyThingCategory thing)
reifyAxBranch :: CoAxBranch -> TcM TH.TySynEqn
reifyAxBranch (CoAxBranch { cab_lhs = args, cab_rhs = rhs })
= do { args' <- mapM reifyType (filter (not . isKind) args)
; rhs' <- reifyType rhs
; return (TH.TySynEqn args' rhs') }
reifyTyCon :: TyCon -> TcM TH.Info
reifyTyCon tc
| Just cls <- tyConClass_maybe tc
= reifyClass cls
| isFunTyCon tc
= return (TH.PrimTyConI (reifyName tc) 2 False)
| isPrimTyCon tc
= return (TH.PrimTyConI (reifyName tc) (tyConArity tc) (isUnLiftedTyCon tc))
| isFamilyTyCon tc
= do { let tvs = tyConTyVars tc
kind = tyConKind tc
(kvs, mono_kind) = splitForAllTys kind
(_, res_kind) = splitKindFunTysN (tyConArity tc length kvs)
mono_kind
; kind' <- fmap Just (reifyKind res_kind)
; tvs' <- reifyTyVars tvs
; flav' <- reifyFamFlavour tc
; case flav' of
{ Left flav ->
do { fam_envs <- tcGetFamInstEnvs
; instances <- mapM reifyFamilyInstance (familyInstances fam_envs tc)
; return (TH.FamilyI
(TH.FamilyD flav (reifyName tc) tvs' kind')
instances) }
; Right eqns ->
return (TH.FamilyI
(TH.ClosedTypeFamilyD (reifyName tc) tvs' kind' eqns)
[]) } }
| Just (tvs, rhs) <- synTyConDefn_maybe tc
= do { rhs' <- reifyType rhs
; tvs' <- reifyTyVars tvs
; return (TH.TyConI
(TH.TySynD (reifyName tc) tvs' rhs'))
}
| otherwise
= do { cxt <- reifyCxt (tyConStupidTheta tc)
; let tvs = tyConTyVars tc
; cons <- mapM (reifyDataCon (mkTyVarTys tvs)) (tyConDataCons tc)
; r_tvs <- reifyTyVars tvs
; let name = reifyName tc
deriv = []
decl | isNewTyCon tc = TH.NewtypeD cxt name r_tvs (head cons) deriv
| otherwise = TH.DataD cxt name r_tvs cons deriv
; return (TH.TyConI decl) }
reifyDataCon :: [Type] -> DataCon -> TcM TH.Con
reifyDataCon tys dc
= do { let (tvs, theta, arg_tys, _) = dataConSig dc
subst = mkTopTvSubst (tvs `zip` tys)
(subst', ex_tvs') = mapAccumL substTyVarBndr subst (dropList tys tvs)
theta' = substTheta subst' theta
arg_tys' = substTys subst' arg_tys
stricts = map reifyStrict (dataConStrictMarks dc)
fields = dataConFieldLabels dc
name = reifyName dc
; r_arg_tys <- reifyTypes arg_tys'
; let main_con | not (null fields)
= TH.RecC name (zip3 (map reifyName fields) stricts r_arg_tys)
| dataConIsInfix dc
= ASSERT( length arg_tys == 2 )
TH.InfixC (s1,r_a1) name (s2,r_a2)
| otherwise
= TH.NormalC name (stricts `zip` r_arg_tys)
[r_a1, r_a2] = r_arg_tys
[s1, s2] = stricts
; ASSERT( length arg_tys == length stricts )
if null ex_tvs' && null theta then
return main_con
else do
{ cxt <- reifyCxt theta'
; ex_tvs'' <- reifyTyVars ex_tvs'
; return (TH.ForallC ex_tvs'' cxt main_con) } }
reifyClass :: Class -> TcM TH.Info
reifyClass cls
= do { cxt <- reifyCxt theta
; inst_envs <- tcGetInstEnvs
; insts <- mapM reifyClassInstance (InstEnv.classInstances inst_envs cls)
; ops <- mapM reify_op op_stuff
; tvs' <- reifyTyVars tvs
; let dec = TH.ClassD cxt (reifyName cls) tvs' fds' ops
; return (TH.ClassI dec insts ) }
where
(tvs, fds, theta, _, _, op_stuff) = classExtraBigSig cls
fds' = map reifyFunDep fds
reify_op (op, _) = do { ty <- reifyType (idType op)
; return (TH.SigD (reifyName op) ty) }
reifyClassInstance :: ClsInst -> TcM TH.Dec
reifyClassInstance i
= do { cxt <- reifyCxt (drop n_silent theta)
; thtypes <- reifyTypes types
; let head_ty = mkThAppTs (TH.ConT (reifyName cls)) thtypes
; return $ (TH.InstanceD cxt head_ty []) }
where
(_tvs, theta, cls, types) = tcSplitDFunTy (idType dfun)
dfun = instanceDFunId i
n_silent = dfunNSilent dfun
reifyFamilyInstance :: FamInst -> TcM TH.Dec
reifyFamilyInstance (FamInst { fi_flavor = flavor
, fi_fam = fam
, fi_tys = lhs
, fi_rhs = rhs })
= case flavor of
SynFamilyInst ->
do { th_lhs <- reifyTypes (filter (not . isKind) lhs)
; th_rhs <- reifyType rhs
; return (TH.TySynInstD (reifyName fam) (TH.TySynEqn th_lhs th_rhs)) }
DataFamilyInst rep_tc ->
do { let tvs = tyConTyVars rep_tc
fam' = reifyName fam
; cons <- mapM (reifyDataCon (mkTyVarTys tvs)) (tyConDataCons rep_tc)
; th_tys <- reifyTypes lhs
; return (if isNewTyCon rep_tc
then TH.NewtypeInstD [] fam' th_tys (head cons) []
else TH.DataInstD [] fam' th_tys cons []) }
reifyType :: TypeRep.Type -> TcM TH.Type
reifyType ty@(ForAllTy _ _) = reify_for_all ty
reifyType (LitTy t) = do { r <- reifyTyLit t; return (TH.LitT r) }
reifyType (TyVarTy tv) = return (TH.VarT (reifyName tv))
reifyType (TyConApp tc tys) = reify_tc_app tc tys
reifyType (AppTy t1 t2) = do { [r1,r2] <- reifyTypes [t1,t2] ; return (r1 `TH.AppT` r2) }
reifyType ty@(FunTy t1 t2)
| isPredTy t1 = reify_for_all ty
| otherwise = do { [r1,r2] <- reifyTypes [t1,t2] ; return (TH.ArrowT `TH.AppT` r1 `TH.AppT` r2) }
reify_for_all :: TypeRep.Type -> TcM TH.Type
reify_for_all ty
= do { cxt' <- reifyCxt cxt;
; tau' <- reifyType tau
; tvs' <- reifyTyVars tvs
; return (TH.ForallT tvs' cxt' tau') }
where
(tvs, cxt, tau) = tcSplitSigmaTy ty
reifyTyLit :: TypeRep.TyLit -> TcM TH.TyLit
reifyTyLit (NumTyLit n) = return (TH.NumTyLit n)
reifyTyLit (StrTyLit s) = return (TH.StrTyLit (unpackFS s))
reifyTypes :: [Type] -> TcM [TH.Type]
reifyTypes = mapM reifyType
reifyKind :: Kind -> TcM TH.Kind
reifyKind ki
= do { let (kis, ki') = splitKindFunTys ki
; ki'_rep <- reifyNonArrowKind ki'
; kis_rep <- mapM reifyKind kis
; return (foldr (TH.AppT . TH.AppT TH.ArrowT) ki'_rep kis_rep) }
where
reifyNonArrowKind k | isLiftedTypeKind k = return TH.StarT
| isConstraintKind k = return TH.ConstraintT
reifyNonArrowKind (TyVarTy v) = return (TH.VarT (reifyName v))
reifyNonArrowKind (ForAllTy _ k) = reifyKind k
reifyNonArrowKind (TyConApp kc kis) = reify_kc_app kc kis
reifyNonArrowKind (AppTy k1 k2) = do { k1' <- reifyKind k1
; k2' <- reifyKind k2
; return (TH.AppT k1' k2')
}
reifyNonArrowKind k = noTH (sLit "this kind") (ppr k)
reify_kc_app :: TyCon -> [TypeRep.Kind] -> TcM TH.Kind
reify_kc_app kc kis
= fmap (mkThAppTs r_kc) (mapM reifyKind kis)
where
r_kc | Just tc <- isPromotedTyCon_maybe kc
, isTupleTyCon tc = TH.TupleT (tyConArity kc)
| kc `hasKey` listTyConKey = TH.ListT
| otherwise = TH.ConT (reifyName kc)
reifyCxt :: [PredType] -> TcM [TH.Pred]
reifyCxt = mapM reifyPred
reifyFunDep :: ([TyVar], [TyVar]) -> TH.FunDep
reifyFunDep (xs, ys) = TH.FunDep (map reifyName xs) (map reifyName ys)
reifyFamFlavour :: TyCon -> TcM (Either TH.FamFlavour [TH.TySynEqn])
reifyFamFlavour tc
| isOpenSynFamilyTyCon tc = return $ Left TH.TypeFam
| isDataFamilyTyCon tc = return $ Left TH.DataFam
| Just ax <- isClosedSynFamilyTyCon_maybe tc
= do { eqns <- brListMapM reifyAxBranch $ coAxiomBranches ax
; return $ Right eqns }
| otherwise
= panic "TcSplice.reifyFamFlavour: not a type family"
reifyTyVars :: [TyVar]
-> TcM [TH.TyVarBndr]
reifyTyVars tvs = mapM reify_tv $ filter isTypeVar tvs
where
reify_tv tv | isLiftedTypeKind kind = return (TH.PlainTV name)
| otherwise = do kind' <- reifyKind kind
return (TH.KindedTV name kind')
where
kind = tyVarKind tv
name = reifyName tv
reify_tc_app :: TyCon -> [TypeRep.Type] -> TcM TH.Type
reify_tc_app tc tys
= do { tys' <- reifyTypes (removeKinds (tyConKind tc) tys)
; return (mkThAppTs r_tc tys') }
where
arity = tyConArity tc
r_tc | isTupleTyCon tc = if isPromotedDataCon tc
then TH.PromotedTupleT arity
else TH.TupleT arity
| tc `hasKey` listTyConKey = TH.ListT
| tc `hasKey` nilDataConKey = TH.PromotedNilT
| tc `hasKey` consDataConKey = TH.PromotedConsT
| otherwise = TH.ConT (reifyName tc)
removeKinds :: Kind -> [TypeRep.Type] -> [TypeRep.Type]
removeKinds (FunTy k1 k2) (h:t)
| isSuperKind k1 = removeKinds k2 t
| otherwise = h : removeKinds k2 t
removeKinds (ForAllTy v k) (h:t)
| isSuperKind (varType v) = removeKinds k t
| otherwise = h : removeKinds k t
removeKinds _ tys = tys
reifyPred :: TypeRep.PredType -> TcM TH.Pred
reifyPred ty
| isIPPred ty = noTH (sLit "implicit parameters") (ppr ty)
| otherwise
= case classifyPredType ty of
ClassPred cls tys -> do { tys' <- reifyTypes tys
; return $ TH.ClassP (reifyName cls) tys' }
EqPred ty1 ty2 -> do { ty1' <- reifyType ty1
; ty2' <- reifyType ty2
; return $ TH.EqualP ty1' ty2'
}
TuplePred _ -> noTH (sLit "tuple predicates") (ppr ty)
IrredPred _ -> noTH (sLit "irreducible predicates") (ppr ty)
reifyName :: NamedThing n => n -> TH.Name
reifyName thing
| isExternalName name = mk_varg pkg_str mod_str occ_str
| otherwise = TH.mkNameU occ_str (getKey (getUnique name))
where
name = getName thing
mod = ASSERT( isExternalName name ) nameModule name
pkg_str = packageIdString (modulePackageId mod)
mod_str = moduleNameString (moduleName mod)
occ_str = occNameString occ
occ = nameOccName name
mk_varg | OccName.isDataOcc occ = TH.mkNameG_d
| OccName.isVarOcc occ = TH.mkNameG_v
| OccName.isTcOcc occ = TH.mkNameG_tc
| otherwise = pprPanic "reifyName" (ppr name)
reifyFixity :: Name -> TcM TH.Fixity
reifyFixity name
= do { fix <- lookupFixityRn name
; return (conv_fix fix) }
where
conv_fix (BasicTypes.Fixity i d) = TH.Fixity i (conv_dir d)
conv_dir BasicTypes.InfixR = TH.InfixR
conv_dir BasicTypes.InfixL = TH.InfixL
conv_dir BasicTypes.InfixN = TH.InfixN
reifyStrict :: DataCon.HsBang -> TH.Strict
reifyStrict HsNoBang = TH.NotStrict
reifyStrict (HsUserBang _ False) = TH.NotStrict
reifyStrict (HsUserBang (Just True) True) = TH.Unpacked
reifyStrict (HsUserBang _ True) = TH.IsStrict
reifyStrict HsStrict = TH.IsStrict
reifyStrict (HsUnpack {}) = TH.Unpacked
lookupThAnnLookup :: TH.AnnLookup -> TcM CoreAnnTarget
lookupThAnnLookup (TH.AnnLookupName th_nm) = fmap NamedTarget (lookupThName th_nm)
lookupThAnnLookup (TH.AnnLookupModule (TH.Module pn mn))
= return $ ModuleTarget $
mkModule (stringToPackageId $ TH.pkgString pn) (mkModuleName $ TH.modString mn)
reifyAnnotations :: Data a => TH.AnnLookup -> TcM [a]
reifyAnnotations th_name
= do { name <- lookupThAnnLookup th_name
; topEnv <- getTopEnv
; epsHptAnns <- liftIO $ prepareAnnotations topEnv Nothing
; tcg <- getGblEnv
; let selectedEpsHptAnns = findAnns deserializeWithData epsHptAnns name
; let selectedTcgAnns = findAnns deserializeWithData (tcg_ann_env tcg) name
; return (selectedEpsHptAnns ++ selectedTcgAnns) }
modToTHMod :: Module -> TH.Module
modToTHMod m = TH.Module (TH.PkgName $ packageIdString $ modulePackageId m)
(TH.ModName $ moduleNameString $ moduleName m)
reifyModule :: TH.Module -> TcM TH.ModuleInfo
reifyModule (TH.Module (TH.PkgName pkgString) (TH.ModName mString)) = do
this_mod <- getModule
let reifMod = mkModule (stringToPackageId pkgString) (mkModuleName mString)
if (reifMod == this_mod) then reifyThisModule else reifyFromIface reifMod
where
reifyThisModule = do
usages <- fmap (map modToTHMod . moduleEnvKeys . imp_mods) getImports
return $ TH.ModuleInfo usages
reifyFromIface reifMod = do
iface <- loadInterfaceForModule (ptext (sLit "reifying module from TH for") <+> ppr reifMod) reifMod
let usages = [modToTHMod m | usage <- mi_usages iface,
Just m <- [usageToModule (modulePackageId reifMod) usage] ]
return $ TH.ModuleInfo usages
usageToModule :: PackageId -> Usage -> Maybe Module
usageToModule _ (UsageFile {}) = Nothing
usageToModule this_pkg (UsageHomeModule { usg_mod_name = mn }) = Just $ mkModule this_pkg mn
usageToModule _ (UsagePackageModule { usg_mod = m }) = Just m
mkThAppTs :: TH.Type -> [TH.Type] -> TH.Type
mkThAppTs fun_ty arg_tys = foldl TH.AppT fun_ty arg_tys
noTH :: LitString -> SDoc -> TcM a
noTH s d = failWithTc (hsep [ptext (sLit "Can't represent") <+> ptext s <+>
ptext (sLit "in Template Haskell:"),
nest 2 d])
ppr_th :: TH.Ppr a => a -> SDoc
ppr_th x = text (TH.pprint x)
\end{code}
Note [Reifying data constructors]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Template Haskell syntax is rich enough to express even GADTs,
provided we do so in the equality-predicate form. So a GADT
like
data T a where
MkT1 :: a -> T [a]
MkT2 :: T Int
will appear in TH syntax like this
data T a = forall b. (a ~ [b]) => MkT1 b
| (a ~ Int) => MkT2
\begin{code}
#endif /* GHCI */
\end{code}