TcSplice: Template Haskell splices
+
\begin{code}
{-# OPTIONS -fno-warn-unused-imports -fno-warn-unused-binds #-}
-- The above warning supression flag is a temporary kludge.
-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
-- for details
-module TcSplice( tcSpliceExpr, tcSpliceDecls, tcBracket,
- runQuasiQuoteExpr, runQuasiQuotePat ) where
+module TcSplice( kcSpliceType, tcSpliceExpr, tcSpliceDecls, tcBracket,
+ lookupThName_maybe,
+ runQuasiQuoteExpr, runQuasiQuotePat,
+ runQuasiQuoteDecl, runQuasiQuoteType,
+ runAnnotation ) where
#include "HsVersions.h"
import RnEnv
import RdrName
import RnTypes
+import TcPat
import TcExpr
import TcHsSyn
import TcSimplify
import TcHsType
import TcIface
import TypeRep
+import InstEnv
import Name
import NameEnv
+import NameSet
+import PrelNames
import HscTypes
import OccName
import Var
import Module
+import Annotations
import TcRnMonad
import Class
+import Inst
import TyCon
import DataCon
import Id
import DsMeta
import DsExpr
import DsMonad hiding (Splice)
+import Serialized
import ErrUtils
import SrcLoc
import Outputable
+import Util ( dropList )
+import Data.List ( mapAccumL )
+import Pair
import Unique
-import Maybe
+import Data.Maybe
import BasicTypes
import Panic
import FastString
+import Exception
+import Control.Monad ( when )
import qualified Language.Haskell.TH as TH
-- THSyntax gives access to internal functions and data types
import qualified Language.Haskell.TH.Syntax as TH
+#ifdef GHCI
+-- Because GHC.Desugar might not be in the base library of the bootstrapping compiler
+import GHC.Desugar ( AnnotationWrapper(..) )
+#endif
+
import GHC.Exts ( unsafeCoerce#, Int#, Int(..) )
-import qualified Control.Exception as Exception( userErrors )
+import System.IO.Error
\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, becuase 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.
+
+ * After typechecking, the bracket [| |] carries
+
+ a) A mutable list of PendingSplice
+ type PendingSplice = (Name, LHsExpr Id)
+
+ b) The quoted expression e, *renamed*: (HsExpr Name)
+ The expression e has been typechecked, but the result of
+ that typechecking is discarded.
+
+ * The brakcet 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 the type checker type-checks a nested splice ${n}(e), it
+ - typechecks e
+ - adds the typechecked expression (of type (HsExpr Id))
+ as a pending splice to the enclosing bracket
+ - returns something non-committal
+ Eg for [| f ${n}(g x) |], the typechecker
+ - attaches the typechecked term (g x) to the pending splices for n
+ in the outer bracket
+ - returns a non-committal type \alpha.
+ Remember that the bracket discards the typechecked term altogether
+
+ * 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)
* Variables are bound at the "current level"
-* The current level starts off at topLevel (= 1)
+* The current level starts off at outerLevel (= 1)
* The level is decremented by splicing $(..)
incremented by brackets [| |]
%************************************************************************
\begin{code}
+tcBracket :: HsBracket Name -> TcRhoType -> TcM (LHsExpr TcId)
tcSpliceDecls :: LHsExpr Name -> TcM [LHsDecl RdrName]
-tcSpliceExpr :: HsSplice Name -> BoxyRhoType -> TcM (HsExpr TcId)
-kcSpliceType :: HsSplice Name -> TcM (HsType Name, TcKind)
+tcSpliceExpr :: HsSplice Name -> TcRhoType -> TcM (HsExpr TcId)
+kcSpliceType :: HsSplice Name -> FreeVars -> TcM (HsType Name, TcKind)
-- None of these functions add constraints to the LIE
-runQuasiQuoteExpr :: HsQuasiQuote Name -> TcM (LHsExpr RdrName)
-runQuasiQuotePat :: HsQuasiQuote Name -> TcM (LPat RdrName)
+lookupThName_maybe :: TH.Name -> TcM (Maybe Name)
+
+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
-tcSpliceExpr _ e _ = pprPanic "Cant do tcSpliceExpr without GHCi" (ppr e)
-tcSpliceDecls e = pprPanic "Cant do tcSpliceDecls without GHCi" (ppr e)
+tcBracket x _ = pprPanic "Cant do tcBracket without GHCi" (ppr x)
+tcSpliceExpr e = pprPanic "Cant do tcSpliceExpr without GHCi" (ppr e)
+tcSpliceDecls x = pprPanic "Cant do tcSpliceDecls without GHCi" (ppr x)
+kcSpliceType x fvs = pprPanic "Cant do kcSpliceType without GHCi" (ppr x)
+
+lookupThName_maybe n = pprPanic "Cant do lookupThName_maybe without GHCi" (ppr n)
runQuasiQuoteExpr q = pprPanic "Cant do runQuasiQuoteExpr without GHCi" (ppr q)
runQuasiQuotePat q = pprPanic "Cant do runQuasiQuotePat without GHCi" (ppr q)
+runQuasiQuoteType q = pprPanic "Cant do runQuasiQuoteType without GHCi" (ppr q)
+runQuasiQuoteDecl q = pprPanic "Cant do runQuasiQuoteDecl without GHCi" (ppr q)
+runAnnotation _ q = pprPanic "Cant do runAnnotation without GHCi" (ppr q)
#else
\end{code}
%* *
%************************************************************************
-Note [Handling brackets]
-~~~~~~~~~~~~~~~~~~~~~~~~
-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) }
\begin{code}
-tcBracket :: HsBracket Name -> BoxyRhoType -> TcM (LHsExpr TcId)
-tcBracket brack res_ty = do
- level <- getStage
- case bracketOK level of {
- Nothing -> failWithTc (illegalBracket level) ;
- Just next_level -> do
+-- See Note [How brackets and nested splices are handled]
+tcBracket brack res_ty
+ = addErrCtxt (hang (ptext (sLit "In the Template Haskell quotation"))
+ 2 (ppr brack)) $
+ do { -- Check for nested brackets
+ cur_stage <- getStage
+ ; checkTc (not (isBrackStage cur_stage)) illegalBracket
+
+ -- Brackets are desugared to code that mentions the TH package
+ ; recordThUse
-- Typecheck expr to make sure it is valid,
-- but throw away the results. We'll type check
-- it again when we actually use it.
- recordThUse
- pending_splices <- newMutVar []
- lie_var <- getLIEVar
-
- (meta_ty, lie) <- setStage (Brack next_level pending_splices lie_var)
- (getLIE (tc_bracket next_level brack))
- tcSimplifyBracket lie
-
- -- Make the expected type have the right shape
- boxyUnify meta_ty res_ty
-
- -- Return the original expression, not the type-decorated one
- pendings <- readMutVar pending_splices
- return (noLoc (HsBracketOut brack pendings))
- }
-
-tc_bracket :: ThLevel -> HsBracket Name -> TcM TcType
-tc_bracket use_lvl (VarBr name) -- Note [Quoting names]
+ ; pending_splices <- newMutVar []
+ ; lie_var <- getConstraintVar
+ ; let brack_stage = Brack cur_stage pending_splices lie_var
+
+ -- We want to check that there aren't any constraints that
+ -- can't be satisfied (e.g. Show Foo, where Foo has no Show
+ -- instance), but we aren't otherwise interested in the
+ -- results. Nor do we care about ambiguous dictionaries etc.
+ -- We will type check this bracket again at its usage site.
+ --
+ -- We build a single implication constraint with a BracketSkol;
+ -- that in turn tells simplifyCheck to report only definite
+ -- errors
+ ; (_,lie) <- captureConstraints $
+ newImplication BracketSkol [] [] $
+ setStage brack_stage $
+ do { meta_ty <- tc_bracket cur_stage brack
+ ; unifyType meta_ty res_ty }
+
+ -- It's best to simplify the constraint now, even though in
+ -- principle some later unification might be useful for it,
+ -- because we don't want these essentially-junk TH implication
+ -- contraints floating around nested inside other constraints
+ -- See for example Trac #4949
+ ; _ <- simplifyTop lie
+
+ -- Return the original expression, not the type-decorated one
+ ; pendings <- readMutVar pending_splices
+ ; return (noLoc (HsBracketOut brack pendings)) }
+
+tc_bracket :: ThStage -> HsBracket Name -> TcM TcType
+tc_bracket outer_stage (VarBr name) -- Note [Quoting names]
= do { thing <- tcLookup name
; case thing of
AGlobal _ -> return ()
ATcId { tct_level = bind_lvl, tct_id = id }
- | thTopLevelId id -- C.f thTopLevelId case of
- -> keepAliveTc id -- TcExpr.thBrackId
+ | thTopLevelId id -- C.f TcExpr.checkCrossStageLifting
+ -> keepAliveTc id
| otherwise
- -> do { checkTc (use_lvl == bind_lvl)
+ -> do { checkTc (thLevel outer_stage + 1 == bind_lvl)
(quotedNameStageErr name) }
_ -> pprPanic "th_bracket" (ppr name)
}
tc_bracket _ (ExpBr expr)
- = do { any_ty <- newFlexiTyVarTy liftedTypeKind
- ; tcMonoExpr expr any_ty
+ = do { any_ty <- newFlexiTyVarTy openTypeKind
+ ; _ <- tcMonoExprNC expr any_ty -- NC for no context; tcBracket does that
; tcMetaTy expQTyConName }
- -- Result type is Expr (= Q Exp)
+ -- Result type is ExpQ (= Q Exp)
tc_bracket _ (TypBr typ)
- = do { tcHsSigType ExprSigCtxt typ
+ = do { _ <- tcHsSigTypeNC ThBrackCtxt typ
; tcMetaTy typeQTyConName }
-- Result type is Type (= Q Typ)
-tc_bracket _ (DecBr decls)
- = do { tcTopSrcDecls emptyModDetails decls
- -- Typecheck the declarations, dicarding the result
- -- We'll get all that stuff later, when we splice it in
+tc_bracket _ (DecBrG decls)
+ = do { _ <- tcTopSrcDecls emptyModDetails decls
+ -- Typecheck the declarations, dicarding the result
+ -- We'll get all that stuff later, when we splice it in
- ; decl_ty <- tcMetaTy decTyConName
- ; q_ty <- tcMetaTy qTyConName
- ; return (mkAppTy q_ty (mkListTy decl_ty))
- -- Result type is Q [Dec]
- }
+ -- Top-level declarations in the bracket get unqualified names
+ -- See Note [Top-level Names in Template Haskell decl quotes] in RnNames
+
+ ; tcMetaTy decsQTyConName } -- Result type is Q [Dec]
+
+tc_bracket _ (PatBr pat)
+ = do { any_ty <- newFlexiTyVarTy openTypeKind
+ ; _ <- tcPat ThPatQuote pat any_ty $
+ return ()
+ ; tcMetaTy patQTyConName }
+ -- Result type is PatQ (= Q Pat)
-tc_bracket _ (PatBr _)
- = failWithTc (ptext (sLit "Tempate Haskell pattern brackets are not supported yet"))
+tc_bracket _ (DecBrL _)
+ = panic "tc_bracket: Unexpected DecBrL"
quotedNameStageErr :: Name -> SDoc
quotedNameStageErr v
\begin{code}
tcSpliceExpr (HsSplice name expr) res_ty
= setSrcSpan (getLoc expr) $ do
- level <- getStage
- case spliceOK level of {
- Nothing -> failWithTc (illegalSplice level) ;
- Just next_level ->
+ { stage <- getStage
+ ; case stage of {
+ Splice -> tcTopSplice expr res_ty ;
+ Comp -> tcTopSplice expr res_ty ;
- case level of {
- Comp -> do { e <- tcTopSplice expr res_ty
- ; return (unLoc e) } ;
- Brack _ ps_var lie_var -> do
+ Brack pop_stage ps_var lie_var -> do
+ -- See Note [How brackets and nested splices are handled]
-- A splice inside brackets
-- NB: ignore res_ty, apart from zapping it to a mono-type
-- e.g. [| reverse $(h 4) |]
-- Here (h 4) :: Q Exp
-- but $(h 4) :: forall a.a i.e. anything!
- unBox res_ty
- meta_exp_ty <- tcMetaTy expQTyConName
- expr' <- setStage (Splice next_level) (
- setLIEVar lie_var $
- tcMonoExpr expr meta_exp_ty
- )
+ { meta_exp_ty <- tcMetaTy expQTyConName
+ ; expr' <- setStage pop_stage $
+ setConstraintVar lie_var $
+ tcMonoExpr expr meta_exp_ty
-- Write the pending splice into the bucket
- ps <- readMutVar ps_var
- writeMutVar ps_var ((name,expr') : ps)
+ ; ps <- readMutVar ps_var
+ ; writeMutVar ps_var ((name,expr') : ps)
- return (panic "tcSpliceExpr") -- The returned expression is ignored
-
- ; Splice {} -> panic "tcSpliceExpr Splice"
- }}
-
--- tcTopSplice used to have this:
--- Note that we do not decrement the level (to -1) before
--- typechecking the expression. For example:
--- f x = $( ...$(g 3) ... )
--- The recursive call to tcMonoExpr will simply expand the
--- inner escape before dealing with the outer one
+ ; return (panic "tcSpliceExpr") -- The returned expression is ignored
+ }}}
-tcTopSplice :: LHsExpr Name -> BoxyRhoType -> TcM (LHsExpr Id)
-tcTopSplice expr res_ty = do
- meta_exp_ty <- tcMetaTy expQTyConName
+tcTopSplice :: LHsExpr Name -> TcRhoType -> TcM (HsExpr Id)
+-- Note [How top-level splices are handled]
+tcTopSplice expr res_ty
+ = do { meta_exp_ty <- tcMetaTy expQTyConName
-- Typecheck the expression
- zonked_q_expr <- tcTopSpliceExpr expr meta_exp_ty
+ ; zonked_q_expr <- tcTopSpliceExpr (tcMonoExpr expr meta_exp_ty)
-- Run the expression
- traceTc (text "About to run" <+> ppr zonked_q_expr)
- expr2 <- runMetaE convertToHsExpr zonked_q_expr
-
- traceTc (text "Got result" <+> ppr expr2)
-
- showSplice "expression"
- zonked_q_expr (ppr expr2)
+ ; expr2 <- runMetaE zonked_q_expr
+ ; showSplice "expression" expr (ppr expr2)
-- Rename it, but bale out if there are errors
-- otherwise the type checker just gives more spurious errors
- (exp3, _fvs) <- checkNoErrs (rnLExpr expr2)
+ ; addErrCtxt (spliceResultDoc expr) $ do
+ { (exp3, _fvs) <- checkNoErrs (rnLExpr expr2)
- tcMonoExpr exp3 res_ty
+ ; exp4 <- tcMonoExpr exp3 res_ty
+ ; return (unLoc exp4) } }
+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 :: LHsExpr Name -> TcType -> TcM (LHsExpr Id)
+-------------------
+tcTopSpliceExpr :: TcM (LHsExpr Id) -> TcM (LHsExpr Id)
+-- Note [How top-level splices are handled]
-- Type check an expression that is the body of a top-level splice
-- (the caller will compile and run it)
-tcTopSpliceExpr expr meta_ty
- = checkNoErrs $ -- checkNoErrs: must not try to run the thing
- -- if the type checker fails!
-
- setStage topSpliceStage $ do
+-- Note that set the level to Splice, regardless of the original level,
+-- before typechecking the expression. For example:
+-- f x = $( ...$(g 3) ... )
+-- The recursive call to tcMonoExpr will simply expand the
+-- inner escape before dealing with the outer one
+tcTopSpliceExpr tc_action
+ = checkNoErrs $ -- checkNoErrs: must not try to run the thing
+ -- if the type checker fails!
+ setStage Splice $
+ do { -- Typecheck the expression
+ (expr', lie) <- captureConstraints tc_action
+
+ -- Solve the constraints
+ ; const_binds <- simplifyTop lie
- do { recordThUse -- Record that TH is used (for pkg depdendency)
+ -- Zonk it and tie the knot of dictionary bindings
+ ; zonkTopLExpr (mkHsDictLet (EvBinds const_binds) expr') }
+\end{code}
+
+
+%************************************************************************
+%* *
+ Splicing a type
+%* *
+%************************************************************************
+
+Very like splicing an expression, but we don't yet share code.
+
+\begin{code}
+kcSpliceType splice@(HsSplice name hs_expr) fvs
+ = setSrcSpan (getLoc hs_expr) $ do
+ { stage <- getStage
+ ; case stage of {
+ Splice -> kcTopSpliceType hs_expr ;
+ Comp -> kcTopSpliceType hs_expr ;
+
+ Brack pop_level ps_var lie_var -> do
+ -- See Note [How brackets and nested splices are handled]
+ -- A splice inside brackets
+ { meta_ty <- tcMetaTy typeQTyConName
+ ; expr' <- setStage pop_level $
+ setConstraintVar lie_var $
+ tcMonoExpr hs_expr meta_ty
+
+ -- Write the pending splice into the bucket
+ ; ps <- readMutVar ps_var
+ ; writeMutVar ps_var ((name,expr') : ps)
+
+ -- e.g. [| f (g :: Int -> $(h 4)) |]
+ -- Here (h 4) :: Q Type
+ -- but $(h 4) :: a i.e. any type, of any kind
+
+ ; kind <- newKindVar
+ ; return (HsSpliceTy splice fvs kind, kind)
+ }}}
+
+kcTopSpliceType :: LHsExpr Name -> TcM (HsType Name, TcKind)
+-- Note [How top-level splices are handled]
+kcTopSpliceType expr
+ = do { meta_ty <- tcMetaTy typeQTyConName
-- Typecheck the expression
- ; (expr', lie) <- getLIE (tcMonoExpr expr meta_ty)
-
- -- Solve the constraints
- ; const_binds <- tcSimplifyTop lie
-
- -- And zonk it
- ; zonkTopLExpr (mkHsDictLet const_binds expr') }
+ ; zonked_q_expr <- tcTopSpliceExpr (tcMonoExpr expr meta_ty)
+
+ -- Run the expression
+ ; hs_ty2 <- runMetaT zonked_q_expr
+ ; showSplice "type" expr (ppr hs_ty2)
+
+ -- Rename it, but bale out if there are errors
+ -- otherwise the type checker just gives more spurious errors
+ ; addErrCtxt (spliceResultDoc expr) $ do
+ { let doc = ptext (sLit "In the spliced type") <+> ppr hs_ty2
+ ; hs_ty3 <- checkNoErrs (rnLHsType doc hs_ty2)
+ ; (ty4, kind) <- kcLHsType hs_ty3
+ ; return (unLoc ty4, kind) }}
+\end{code}
+
+%************************************************************************
+%* *
+\subsection{Splicing an expression}
+%* *
+%************************************************************************
+
+\begin{code}
+-- Note [How top-level splices are handled]
+-- Always at top level
+-- Type sig at top of file:
+-- tcSpliceDecls :: LHsExpr Name -> TcM [LHsDecl RdrName]
+tcSpliceDecls expr
+ = do { list_q <- tcMetaTy decsQTyConName -- Q [Dec]
+ ; zonked_q_expr <- tcTopSpliceExpr (tcMonoExpr expr list_q)
+
+ -- Run the expression
+ ; decls <- runMetaD zonked_q_expr
+ ; showSplice "declarations" expr
+ (ppr (getLoc expr) $$ (vcat (map ppr decls)))
+
+ ; return decls }
+\end{code}
+
+
+%************************************************************************
+%* *
+ Annotations
+%* *
+%************************************************************************
+
+\begin{code}
+runAnnotation target expr = do
+ -- Find the classes we want instances for in order to call toAnnotationWrapper
+ loc <- getSrcSpanM
+ data_class <- tcLookupClass dataClassName
+ to_annotation_wrapper_id <- tcLookupId toAnnotationWrapperName
+
+ -- Check the instances we require live in another module (we want to execute it..)
+ -- and check identifiers live in other modules using TH stage checks. tcSimplifyStagedExpr
+ -- also resolves the LIE constraints to detect e.g. instance ambiguity
+ zonked_wrapped_expr' <- tcTopSpliceExpr $
+ do { (expr', expr_ty) <- tcInferRhoNC expr
+ -- We manually wrap the typechecked expression in a call to toAnnotationWrapper
+ -- By instantiating the call >here< it gets registered in the
+ -- LIE consulted by tcTopSpliceExpr
+ -- and hence ensures the appropriate dictionary is bound by const_binds
+ ; 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')) }
+
+ -- Run the appropriately wrapped expression to get the value of
+ -- the annotation and its dictionaries. The return value is of
+ -- type AnnotationWrapper by construction, so this conversion is
+ -- safe
+ flip runMetaAW zonked_wrapped_expr' $ \annotation_wrapper ->
+ case annotation_wrapper of
+ AnnotationWrapper value | let serialized = toSerialized serializeWithData value ->
+ -- Got the value and dictionaries: build the serialized value and
+ -- call it a day. We ensure that we seq the entire serialized value
+ -- in order that any errors in the user-written code for the
+ -- annotation are exposed at this point. This is also why we are
+ -- doing all this stuff inside the context of runMeta: it has the
+ -- facilities to deal with user error in a meta-level expression
+ seqSerialized serialized `seq` Annotation {
+ ann_target = target,
+ ann_value = serialized
+ }
\end{code}
Workshop 2007).
Briefly, one writes
- [:p| stuff |]
+ [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
However, you can do this in patterns as well as terms. Becuase 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 Name -- Contains term of type QuasiQuoter, and the String
+ => HsQuasiQuote RdrName -- Contains term of type QuasiQuoter, and the String
-> Name -- Of type QuasiQuoter -> String -> Q th_syn
- -> String -- Documentation string only
-> Name -- Name of th_syn type
- -> (SrcSpan -> th_syn -> Either Message hs_syn)
- -> TcM hs_syn
-runQuasiQuote (HsQuasiQuote _name quoter q_span quote) quote_selector desc meta_ty convert
- = do { -- Check that the quoter is not locally defined, otherwise the TH
+ -> MetaOps th_syn hs_syn
+ -> RnM hs_syn
+runQuasiQuote (HsQuasiQuote quoter q_span quote) quote_selector meta_ty meta_ops
+ = do { -- Drop the leading "$" from the quoter name, if present
+ -- This is old-style syntax, now deprecated
+ -- NB: when removing this backward-compat, remove
+ -- the matching code in Lexer.x (around line 310)
+ let occ_str = occNameString (rdrNameOcc quoter)
+ ; quoter <- ASSERT( not (null occ_str) ) -- Lexer ensures this
+ if head occ_str /= '$' then return quoter
+ else do { addWarn (deprecatedDollar quoter)
+ ; return (mkRdrUnqual (mkVarOcc (tail occ_str))) }
+
+ ; quoter' <- lookupOccRn quoter
+ -- We use lookupOcc rather than lookupGlobalOcc because in the
+ -- erroneous case of \x -> [x| ...|] we get a better error message
+ -- (stage restriction rather than out of scope).
+
+ ; when (isUnboundName quoter') failM
+ -- If 'quoter' is not in scope, proceed no further
+ -- The error message was generated by lookupOccRn, but it then
+ -- succeeds with an "unbound name", which makes the subsequent
+ -- attempt to run the quote fail in a confusing way
+
+ -- Check that the quoter is not locally defined, otherwise the TH
-- machinery will not be able to run the quasiquote.
- ; this_mod <- getModule
- ; let is_local = case nameModule_maybe quoter of
- Just mod | mod == this_mod -> True
- | otherwise -> False
- Nothing -> True
- ; traceTc (text "runQQ" <+> ppr quoter <+> ppr is_local)
- ; checkTc (not is_local) (quoteStageError quoter)
+ ; this_mod <- getModule
+ ; let is_local = nameIsLocalOrFrom this_mod quoter'
+ ; checkTc (not is_local) (quoteStageError quoter')
+
+ ; traceTc "runQQ" (ppr quoter <+> ppr is_local)
-- Build the expression
- ; let quoterExpr = L q_span $! HsVar $! quoter
+ ; 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
- ; recordThUse
; meta_exp_ty <- tcMetaTy meta_ty
-- Typecheck the expression
- ; zonked_q_expr <- tcTopSpliceExpr expr meta_exp_ty
+ ; zonked_q_expr <- tcTopSpliceExpr (tcMonoExpr expr meta_exp_ty)
-- Run the expression
- ; traceTc (text "About to run" <+> ppr zonked_q_expr)
- ; result <- runMeta convert zonked_q_expr
- ; traceTc (text "Got result" <+> ppr result)
- ; showSplice desc zonked_q_expr (ppr result)
- ; return result
- }
+ ; result <- runMetaQ meta_ops zonked_q_expr
+ ; showSplice (mt_desc meta_ops) quoteExpr (ppr result)
-runQuasiQuoteExpr quasiquote
- = runQuasiQuote quasiquote quoteExpName "expression" expQTyConName convertToHsExpr
+ ; return result }
-runQuasiQuotePat quasiquote
- = runQuasiQuote quasiquote quotePatName "pattern" patQTyConName convertToPat
+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}
%************************************************************************
%* *
- Splicing a type
+\subsection{Running an expression}
%* *
%************************************************************************
-Very like splicing an expression, but we don't yet share code.
-
\begin{code}
-kcSpliceType (HsSplice name hs_expr)
- = setSrcSpan (getLoc hs_expr) $ do
- { level <- getStage
- ; case spliceOK level of {
- Nothing -> failWithTc (illegalSplice level) ;
- Just next_level -> do
-
- { case level of {
- Comp -> do { (t,k) <- kcTopSpliceType hs_expr
- ; return (unLoc t, k) } ;
- Brack _ ps_var lie_var -> do
-
- { -- A splice inside brackets
- ; meta_ty <- tcMetaTy typeQTyConName
- ; expr' <- setStage (Splice next_level) $
- setLIEVar lie_var $
- tcMonoExpr hs_expr meta_ty
-
- -- Write the pending splice into the bucket
- ; ps <- readMutVar ps_var
- ; writeMutVar ps_var ((name,expr') : ps)
-
- -- e.g. [| Int -> $(h 4) |]
- -- Here (h 4) :: Q Type
- -- but $(h 4) :: forall a.a i.e. any kind
- ; kind <- newKindVar
- ; return (panic "kcSpliceType", kind) -- The returned type is ignored
+data MetaOps th_syn hs_syn
+ = MT { mt_desc :: String -- Type of beast (expression, type etc)
+ , mt_show :: th_syn -> String -- How to show the th_syn thing
+ , mt_cvt :: SrcSpan -> th_syn -> Either Message hs_syn
+ -- How to convert to hs_syn
}
- ; Splice {} -> panic "kcSpliceType Splice"
- }}}}
-
-kcTopSpliceType :: LHsExpr Name -> TcM (LHsType Name, TcKind)
-kcTopSpliceType expr
- = do { meta_ty <- tcMetaTy typeQTyConName
-
- -- Typecheck the expression
- ; zonked_q_expr <- tcTopSpliceExpr expr meta_ty
-
- -- Run the expression
- ; traceTc (text "About to run" <+> ppr zonked_q_expr)
- ; hs_ty2 <- runMetaT convertToHsType zonked_q_expr
-
- ; traceTc (text "Got result" <+> ppr hs_ty2)
-
- ; showSplice "type" zonked_q_expr (ppr hs_ty2)
-
- -- Rename it, but bale out if there are errors
- -- otherwise the type checker just gives more spurious errors
- ; let doc = ptext (sLit "In the spliced type") <+> ppr hs_ty2
- ; hs_ty3 <- checkNoErrs (rnLHsType doc hs_ty2)
-
- ; kcHsType hs_ty3 }
-\end{code}
-
-%************************************************************************
-%* *
-\subsection{Splicing an expression}
-%* *
-%************************************************************************
-
-\begin{code}
--- Always at top level
--- Type sig at top of file:
--- tcSpliceDecls :: LHsExpr Name -> TcM [LHsDecl RdrName]
-tcSpliceDecls expr
- = do { meta_dec_ty <- tcMetaTy decTyConName
- ; meta_q_ty <- tcMetaTy qTyConName
- ; let list_q = mkAppTy meta_q_ty (mkListTy meta_dec_ty)
- ; zonked_q_expr <- tcTopSpliceExpr expr list_q
-
- -- Run the expression
- ; traceTc (text "About to run" <+> ppr zonked_q_expr)
- ; decls <- runMetaD convertToHsDecls zonked_q_expr
-
- ; traceTc (text "Got result" <+> vcat (map ppr decls))
- ; showSplice "declarations"
- zonked_q_expr
- (ppr (getLoc expr) $$ (vcat (map ppr decls)))
- ; return decls }
-\end{code}
-
-%************************************************************************
-%* *
-\subsection{Running an expression}
-%* *
-%************************************************************************
+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 -- Of type AnnotationWrapper
+ -> TcM output
+runMetaAW k = runMeta False (\_ -> return . Right . k)
+ -- We turn off showing the code in meta-level exceptions because doing so exposes
+ -- the toAnnotationWrapper function that we slap around the users code
+
+-----------------
+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) }
-\begin{code}
-runMetaE :: (SrcSpan -> TH.Exp -> Either Message (LHsExpr RdrName))
- -> LHsExpr Id -- Of type (Q Exp)
+runMetaE :: LHsExpr Id -- Of type (Q Exp)
-> TcM (LHsExpr RdrName)
-runMetaE = runMeta
-
-runMetaP :: (SrcSpan -> TH.Pat -> Either Message (Pat RdrName))
- -> LHsExpr Id -- Of type (Q Pat)
- -> TcM (Pat RdrName)
-runMetaP = runMeta
+runMetaE = runMetaQ exprMetaOps
-runMetaT :: (SrcSpan -> TH.Type -> Either Message (LHsType RdrName))
- -> LHsExpr Id -- Of type (Q Type)
+runMetaT :: LHsExpr Id -- Of type (Q Type)
-> TcM (LHsType RdrName)
-runMetaT = runMeta
+runMetaT = runMetaQ typeMetaOps
-runMetaD :: (SrcSpan -> [TH.Dec] -> Either Message [LHsDecl RdrName])
- -> LHsExpr Id -- Of type Q [Dec]
+runMetaD :: LHsExpr Id -- Of type Q [Dec]
-> TcM [LHsDecl RdrName]
-runMetaD = runMeta
+runMetaD = runMetaQ declMetaOps
-runMeta :: (SrcSpan -> th_syn -> Either Message hs_syn)
- -> LHsExpr Id -- Of type X
+---------------
+runMeta :: (Outputable hs_syn)
+ => Bool -- Whether code should be printed in the exception message
+ -> (SrcSpan -> x -> TcM (Either Message hs_syn)) -- How to run x
+ -> LHsExpr Id -- Of type x; typically x = Q TH.Exp, or something like that
-> TcM hs_syn -- Of type t
-runMeta convert expr
- = do { -- Desugar
- ds_expr <- initDsTc (dsLExpr expr)
+runMeta show_code run_and_convert expr
+ = do { traceTc "About to run" (ppr expr)
+
+ -- Desugar
+ ; ds_expr <- initDsTc (dsLExpr expr)
-- Compile and link it; might fail if linking fails
; hsc_env <- getTopEnv
; src_span <- getSrcSpanM
; either_hval <- tryM $ liftIO $
- HscMain.compileExpr hsc_env src_span ds_expr
+ HscMain.hscCompileCoreExpr hsc_env src_span ds_expr
; case either_hval of {
Left exn -> failWithTc (mk_msg "compile and link" exn) ;
Right hval -> do
; either_tval <- tryAllM $
setSrcSpan expr_span $ -- Set the span so that qLocation can
-- see where this splice is
- do { th_syn <- TH.runQ (unsafeCoerce# hval)
- ; case convert expr_span th_syn of
+ do { mb_result <- run_and_convert expr_span (unsafeCoerce# hval)
+ ; case mb_result of
Left err -> failWithTc err
- Right hs_syn -> return hs_syn }
+ Right result -> do { traceTc "Got HsSyn result:" (ppr result)
+ ; return $! result } }
; case either_tval of
Right v -> return v
- Left exn | Just s <- Exception.userErrors exn
- , s == "IOEnv failure"
- -> failM -- Error already in Tc monad
- | otherwise -> failWithTc (mk_msg "run" exn) -- Exception
+ Left se -> case fromException se of
+ Just IOEnvFailure -> failM -- Error already in Tc monad
+ _ -> failWithTc (mk_msg "run" se) -- Exception
}}}
where
mk_msg s exn = vcat [text "Exception when trying to" <+> text s <+> text "compile-time code:",
nest 2 (text (Panic.showException exn)),
- nest 2 (text "Code:" <+> ppr expr)]
+ if show_code then nest 2 (text "Code:" <+> ppr expr) else empty]
\end{code}
Note [Exceptions in TH]
* 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 a UserError, with the uninteresting string
- "IOEnv failure"
+ The 'fail' in TcM raises an IOEnvFailure exception
* So, when running a splice, we catch all exceptions; then for
- - a UserError "IOEnv failure", we assume the error is already
+ - 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
; return (TH.mkNameU s i) }
qReport True msg = addErr (text msg)
- qReport False msg = addReport (text msg)
+ qReport False msg = addReport (text msg) empty
qLocation = do { m <- getModule
- ; l <- getSrcSpanM
- ; return (TH.Loc { TH.loc_filename = unpackFS (srcSpanFile l)
- , TH.loc_module = moduleNameString (moduleName m)
- , TH.loc_package = packageIdString (modulePackageId m)
- , TH.loc_start = (srcSpanStartLine l, srcSpanStartCol l)
- , TH.loc_end = (srcSpanEndLine l, srcSpanEndCol l) }) }
-
+ ; 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) }) }
+
qReify v = reify v
+ qClassInstances = lookupClassInstances
-- For qRecover, discard error messages if
-- the recovery action is chosen. Otherwise
%************************************************************************
\begin{code}
-showSplice :: String -> LHsExpr Id -> 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])])
+showSplice :: String -> LHsExpr Name -> SDoc -> TcM ()
+-- Note that 'before' is *renamed* but not *typechecked*
+-- Reason (a) less typechecking crap
+-- (b) data constructors after type checking have been
+-- changed to their *wrappers*, and that makes them
+-- print always fully qualified
+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])]) }
+
+illegalBracket :: SDoc
+illegalBracket = ptext (sLit "Template Haskell brackets cannot be nested (without intervening splices)")
+#endif /* GHCI */
+\end{code}
-illegalBracket :: ThStage -> SDoc
-illegalBracket level
- = ptext (sLit "Illegal bracket at level") <+> ppr level
-illegalSplice :: ThStage -> SDoc
-illegalSplice level
- = ptext (sLit "Illegal splice at level") <+> ppr level
+%************************************************************************
+%* *
+ Instance Testing
+%* *
+%************************************************************************
-#endif /* GHCI */
+\begin{code}
+lookupClassInstances :: TH.Name -> [TH.Type] -> TcM [TH.ClassInstance]
+lookupClassInstances c ts
+ = do { loc <- getSrcSpanM
+ ; case convertToHsPred loc (TH.ClassP c ts) of {
+ Left msg -> failWithTc msg;
+ Right rdr_pred -> do
+ { rn_pred <- rnLPred doc rdr_pred -- Rename
+ ; kc_pred <- kcHsLPred rn_pred -- Kind check
+ ; ClassP cls tys <- dsHsLPred kc_pred -- Type check
+
+ -- Now look up instances
+ ; inst_envs <- tcGetInstEnvs
+ ; let (matches, unifies) = lookupInstEnv inst_envs cls tys
+ ; mapM reifyClassInstance (map fst matches ++ unifies) } } }
+ where
+ doc = ptext (sLit "TcSplice.classInstances")
\end{code}
ppr_ns _ = panic "reify/ppr_ns"
lookupThName :: TH.Name -> TcM Name
-lookupThName th_name@(TH.Name occ flavour)
- = do { let rdr_name = thRdrName guessed_ns occ_str flavour
-
- -- Repeat much of lookupOccRn, becase we want
- -- to report errors in a TH-relevant way
- ; rdr_env <- getLocalRdrEnv
- ; case lookupLocalRdrEnv rdr_env rdr_name of
- Just name -> return name
- Nothing | not (isSrcRdrName rdr_name) -- Exact, Orig
- -> lookupImportedName rdr_name
- | otherwise -- Unqual, Qual
- -> do { mb_name <- lookupSrcOcc_maybe rdr_name
- ; case mb_name of
- Just name -> return name
- Nothing -> failWithTc (notInScope th_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
+ = do { names <- mapMaybeM lookup (thRdrNameGuesses th_name)
+ -- Pick the first that works
+ -- E.g. reify (mkName "A") will pick the class A in preference to the data constructor A
+ ; return (listToMaybe names) }
where
- -- guessed_ns is the name space guessed from looking at the TH name
- guessed_ns | isLexCon (mkFastString occ_str) = OccName.dataName
- | otherwise = OccName.varName
- occ_str = TH.occString occ
+ lookup rdr_name
+ = do { -- Repeat much of lookupOccRn, becase we want
+ -- to report errors in a TH-relevant way
+ ; rdr_env <- getLocalRdrEnv
+ ; case lookupLocalRdrEnv rdr_env rdr_name of
+ Just name -> return (Just name)
+ Nothing -> lookupGlobalOccRn_maybe rdr_name }
tcLookupTh :: Name -> TcM TcTyThing
-- This is a specialised version of TcEnv.tcLookup; specialised mainly in that
= do { ty <- reifyType (idType id)
; fix <- reifyFixity (idName id)
; let v = reifyName id
- ; case globalIdDetails id of
- ClassOpId cls -> return (TH.ClassOpI v ty (reifyName cls) fix)
- _ -> return (TH.VarI v ty Nothing fix)
+ ; 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 (AClass cls)) = reifyClass cls
+reifyThing (AGlobal (ATyCon tc)) = reifyTyCon tc
+reifyThing (AGlobal (ACoAxiom ax)) = reifyAxiom ax
+reifyThing (AGlobal (AClass cls)) = reifyClass cls
reifyThing (AGlobal (ADataCon dc))
= do { let name = dataConName dc
; ty <- reifyType (idType (dataConWrapId dc))
; fix <- reifyFixity name
- ; return (TH.DataConI (reifyName name) ty (reifyName (dataConTyCon dc)) fix) }
+ ; return (TH.DataConI (reifyName name) ty
+ (reifyName (dataConOrigTyCon dc)) fix)
+ }
-reifyThing (ATcId {tct_id = id, tct_type = ty})
- = do { ty1 <- zonkTcType ty -- Make use of all the info we have, even
- -- though it may be incomplete
+reifyThing (ATcId {tct_id = id})
+ = do { ty1 <- zonkTcType (idType id) -- Make use of all the info we have, even
+ -- though it may be incomplete
; ty2 <- reifyType ty1
; fix <- reifyFixity (idName id)
; return (TH.VarI (reifyName id) ty2 Nothing fix) }
reifyThing (AThing {}) = panic "reifyThing AThing"
------------------------------
+reifyAxiom :: CoAxiom -> TcM TH.Info
+reifyAxiom ax@(CoAxiom { co_ax_lhs = lhs, co_ax_rhs = rhs })
+ | Just (tc, args) <- tcSplitTyConApp_maybe lhs
+ = do { args' <- mapM reifyType args
+ ; rhs' <- reifyType rhs
+ ; return (TH.TyConI $ TH.TySynInstD (reifyName tc) args' rhs') }
+ | otherwise
+ = failWith (ptext (sLit "Can't reify the axiom") <+> ppr ax
+ <+> dcolon <+> pprEqPred (Pair lhs rhs))
+
reifyTyCon :: TyCon -> TcM TH.Info
reifyTyCon tc
- | isFunTyCon tc = return (TH.PrimTyConI (reifyName tc) 2 False)
- | isPrimTyCon tc = return (TH.PrimTyConI (reifyName tc) (tyConArity tc) (isUnLiftedTyCon tc))
+ | isFunTyCon tc
+ = return (TH.PrimTyConI (reifyName tc) 2 False)
+
+ | isPrimTyCon tc
+ = return (TH.PrimTyConI (reifyName tc) (tyConArity tc) (isUnLiftedTyCon tc))
+
+ | isFamilyTyCon tc
+ = let flavour = reifyFamFlavour tc
+ tvs = tyConTyVars tc
+ kind = tyConKind tc
+ kind'
+ | isLiftedTypeKind kind = Nothing
+ | otherwise = Just $ reifyKind kind
+ in
+ return (TH.TyConI $
+ TH.FamilyD flavour (reifyName tc) (reifyTyVars tvs) kind')
+
| isSynTyCon tc
= do { let (tvs, rhs) = synTyConDefn tc
; rhs' <- reifyType rhs
; return (TH.TyConI $
- TH.TySynD (reifyName tc) (reifyTyVars tvs) rhs') }
+ TH.TySynD (reifyName tc) (reifyTyVars tvs) rhs')
+ }
-reifyTyCon tc
+ | otherwise
= do { cxt <- reifyCxt (tyConStupidTheta tc)
; let tvs = tyConTyVars tc
; cons <- mapM (reifyDataCon (mkTyVarTys tvs)) (tyConDataCons tc)
r_tvs = reifyTyVars tvs
deriv = [] -- Don't know about deriving
decl | isNewTyCon tc = TH.NewtypeD cxt name r_tvs (head cons) deriv
- | otherwise = TH.DataD cxt name r_tvs cons deriv
+ | otherwise = TH.DataD cxt name r_tvs cons deriv
; return (TH.TyConI decl) }
reifyDataCon :: [Type] -> DataCon -> TcM TH.Con
+-- For GADTs etc, see Note [Reifying data constructors]
reifyDataCon tys dc
- | isVanillaDataCon dc
- = do { arg_tys <- reifyTypes (dataConInstOrigArgTys dc tys)
- ; let stricts = map reifyStrict (dataConStrictMarks dc)
- fields = dataConFieldLabels dc
- name = reifyName dc
- [a1,a2] = arg_tys
- [s1,s2] = stricts
- ; ASSERT( length arg_tys == length stricts )
- if not (null fields) then
- return (TH.RecC name (zip3 (map reifyName fields) stricts arg_tys))
- else
- if dataConIsInfix dc then
- ASSERT( length arg_tys == 2 )
- return (TH.InfixC (s1,a1) name (s2,a2))
- else
- return (TH.NormalC name (stricts `zip` arg_tys)) }
- | otherwise
- = failWithTc (ptext (sLit "Can't reify a non-Haskell-98 data constructor:")
- <+> quotes (ppr dc))
+ = do { let (tvs, theta, arg_tys, _) = dataConSig dc
+ subst = mkTopTvSubst (tvs `zip` tys) -- Dicard ex_tvs
+ (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'
+ ; return (TH.ForallC (reifyTyVars 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
- ; return (TH.ClassI $ TH.ClassD cxt (reifyName cls) (reifyTyVars tvs) fds' ops) }
+ ; let dec = TH.ClassD cxt (reifyName cls) (reifyTyVars tvs) fds' ops
+ ; return (TH.ClassI dec insts ) }
where
(tvs, fds, theta, _, _, op_stuff) = classExtraBigSig cls
fds' = map reifyFunDep fds
; return (TH.SigD (reifyName op) ty) }
------------------------------
+reifyClassInstance :: Instance -> TcM TH.ClassInstance
+reifyClassInstance i
+ = do { cxt <- reifyCxt theta
+ ; thtypes <- reifyTypes types
+ ; return $ (TH.ClassInstance {
+ TH.ci_tvs = reifyTyVars tvs,
+ TH.ci_cxt = cxt,
+ TH.ci_tys = thtypes,
+ TH.ci_cls = reifyName cls,
+ TH.ci_dfun = reifyName (is_dfun i) }) }
+ where
+ (tvs, theta, cls, types) = instanceHead i
+
+------------------------------
reifyType :: TypeRep.Type -> TcM TH.Type
+-- Monadic only because of failure
+reifyType ty@(ForAllTy _ _) = reify_for_all ty
+reifyType ty@(PredTy {} `FunTy` _) = reify_for_all ty -- Types like ((?x::Int) => Char -> Char)
reifyType (TyVarTy tv) = return (TH.VarT (reifyName tv))
-reifyType (TyConApp tc tys) = reify_tc_app (reifyName tc) tys
+reifyType (TyConApp tc tys) = reify_tc_app tc tys -- Do not expand type synonyms here
reifyType (AppTy t1 t2) = do { [r1,r2] <- reifyTypes [t1,t2] ; return (r1 `TH.AppT` r2) }
reifyType (FunTy t1 t2) = do { [r1,r2] <- reifyTypes [t1,t2] ; return (TH.ArrowT `TH.AppT` r1 `TH.AppT` r2) }
-reifyType ty@(ForAllTy _ _) = do { cxt' <- reifyCxt cxt;
- ; tau' <- reifyType tau
- ; return (TH.ForallT (reifyTyVars tvs) cxt' tau') }
- where
- (tvs, cxt, tau) = tcSplitSigmaTy ty
-reifyType (PredTy {}) = panic "reifyType PredTy"
+reifyType ty@(PredTy {}) = pprPanic "reifyType PredTy" (ppr ty)
+reify_for_all :: TypeRep.Type -> TcM TH.Type
+reify_for_all ty
+ = do { cxt' <- reifyCxt cxt;
+ ; tau' <- reifyType tau
+ ; return (TH.ForallT (reifyTyVars tvs) cxt' tau') }
+ where
+ (tvs, cxt, tau) = tcSplitSigmaTy ty
+
reifyTypes :: [Type] -> TcM [TH.Type]
reifyTypes = mapM reifyType
-reifyCxt :: [PredType] -> TcM [TH.Type]
+
+reifyKind :: Kind -> TH.Kind
+reifyKind ki
+ = let (kis, ki') = splitKindFunTys ki
+ kis_rep = map reifyKind kis
+ ki'_rep = reifyNonArrowKind ki'
+ in
+ foldr TH.ArrowK ki'_rep kis_rep
+ where
+ reifyNonArrowKind k | isLiftedTypeKind k = TH.StarK
+ | otherwise = pprPanic "Exotic form of kind"
+ (ppr k)
+
+reifyCxt :: [PredType] -> TcM [TH.Pred]
reifyCxt = mapM reifyPred
reifyFunDep :: ([TyVar], [TyVar]) -> TH.FunDep
reifyFunDep (xs, ys) = TH.FunDep (map reifyName xs) (map reifyName ys)
-reifyTyVars :: [TyVar] -> [TH.Name]
-reifyTyVars = map reifyName
+reifyFamFlavour :: TyCon -> TH.FamFlavour
+reifyFamFlavour tc | isSynFamilyTyCon tc = TH.TypeFam
+ | isFamilyTyCon tc = TH.DataFam
+ | otherwise
+ = panic "TcSplice.reifyFamFlavour: not a type family"
+
+reifyTyVars :: [TyVar] -> [TH.TyVarBndr]
+reifyTyVars = map reifyTyVar
+ where
+ reifyTyVar tv | isLiftedTypeKind kind = TH.PlainTV name
+ | otherwise = TH.KindedTV name (reifyKind 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 tys
+ ; return (foldl TH.AppT r_tc tys') }
+ where
+ n_tys = length tys
+ r_tc | isTupleTyCon tc = TH.TupleT n_tys
+ | tc `hasKey` listTyConKey = TH.ListT
+ | otherwise = TH.ConT (reifyName tc)
-reify_tc_app :: TH.Name -> [TypeRep.Type] -> TcM TH.Type
-reify_tc_app tc tys = do { tys' <- reifyTypes tys
- ; return (foldl TH.AppT (TH.ConT tc) tys') }
+reifyPred :: TypeRep.PredType -> TcM TH.Pred
+reifyPred (ClassP cls tys)
+ = do { tys' <- reifyTypes tys
+ ; return $ TH.ClassP (reifyName cls) tys' }
-reifyPred :: TypeRep.PredType -> TcM TH.Type
-reifyPred (ClassP cls tys) = reify_tc_app (reifyName cls) tys
reifyPred p@(IParam _ _) = noTH (sLit "implicit parameters") (ppr p)
-reifyPred (EqPred {}) = panic "reifyPred EqPred"
+reifyPred (EqPred ty1 ty2)
+ = do { ty1' <- reifyType ty1
+ ; ty2' <- reifyType ty2
+ ; return $ TH.EqualP ty1' ty2'
+ }
------------------------------
-- have free variables, we may need to generate NameL's for them.
where
name = getName thing
- mod = nameModule name
+ mod = ASSERT( isExternalName name ) nameModule name
pkg_str = packageIdString (modulePackageId mod)
mod_str = moduleNameString (moduleName mod)
occ_str = occNameString occ
conv_dir BasicTypes.InfixL = TH.InfixL
conv_dir BasicTypes.InfixN = TH.InfixN
-reifyStrict :: BasicTypes.StrictnessMark -> TH.Strict
-reifyStrict MarkedStrict = TH.IsStrict
-reifyStrict MarkedUnboxed = TH.IsStrict
-reifyStrict NotMarkedStrict = TH.NotStrict
+reifyStrict :: BasicTypes.HsBang -> TH.Strict
+reifyStrict bang | isBanged bang = TH.IsStrict
+ | otherwise = TH.NotStrict
------------------------------
noTH :: LitString -> SDoc -> TcM a
ptext (sLit "in Template Haskell:"),
nest 2 d])
\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
+
projects / ghc-hetmet.git / blobdiff