import MkCore
import MkId
import Id
-import Var
import Name
import Literal
import TyCon
\end{code}
-
%************************************************************************
%* *
Rebindable syntax
selectMatchVar (BangPat pat) = selectMatchVar (unLoc pat)
selectMatchVar (LazyPat pat) = selectMatchVar (unLoc pat)
selectMatchVar (ParPat pat) = selectMatchVar (unLoc pat)
-selectMatchVar (VarPat var) = return var
+selectMatchVar (VarPat var) = return (localiseId var) -- Note [Localise pattern binders]
selectMatchVar (AsPat var _) = return (unLoc var)
selectMatchVar other_pat = newSysLocalDs (hsPatType other_pat)
-- OK, better make up one...
\end{code}
+Note [Localise pattern binders]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider module M where
+ [Just a] = e
+After renaming it looks like
+ module M where
+ [Just M.a] = e
+
+We don't generalise, since it's a pattern binding, monomorphic, etc,
+so after desugaring we may get something like
+ M.a = case e of (v:_) ->
+ case v of Just M.a -> M.a
+Notice the "M.a" in the pattern; after all, it was in the original
+pattern. However, after optimisation those pattern binders can become
+let-binders, and then end up floated to top level. They have a
+different *unique* by then (the simplifier is good about maintaining
+proper scoping), but it's BAD to have two top-level bindings with the
+External Name M.a, because that turns into two linker symbols for M.a.
+It's quite rare for this to actually *happen* -- the only case I know
+of is tc003 compiled with the 'hpc' way -- but that only makes it
+all the more annoying.
+
+To avoid this, we craftily call 'localiseId' in the desugarer, which
+simply turns the External Name for the Id into an Internal one, but
+doesn't change the unique. So the desugarer produces this:
+ M.a{r8} = case e of (v:_) ->
+ case v of Just a{r8} -> M.a{r8}
+The unique is still 'r8', but the binding site in the pattern
+is now an Internal Name. Now the simplifier's usual mechanisms
+will propagate that Name to all the occurrence sites, as well as
+un-shadowing it, so we'll get
+ M.a{r8} = case e of (v:_) ->
+ case v of Just a{s77} -> a{s77}
+In fact, even CoreSubst.simplOptExpr will do this, and simpleOptExpr
+runs on the output of the desugarer, so all is well by the end of
+the desugaring pass.
+
%************************************************************************
%* *
wrapBinds ((new,old):prs) e = wrapBind new old (wrapBinds prs e)
wrapBind :: Var -> Var -> CoreExpr -> CoreExpr
-wrapBind new old body -- Can deal with term variables *or* type variables
- | new==old = body
- | isTyVar new = Let (mkTyBind new (mkTyVarTy old)) body
- | otherwise = Let (NonRec new (Var old)) body
+wrapBind new old body -- NB: this function must deal with term
+ | new==old = body -- variables, type variables or coercion variables
+ | otherwise = Let (NonRec new (varToCoreExpr old)) body
seqVar :: Var -> CoreExpr -> CoreExpr
seqVar var body = Case (Var var) var (exprType body)
return (LitAlt lit, [], body)
-mkCoAlgCaseMatchResult :: Id -- Scrutinee
- -> Type -- Type of exp
- -> [(DataCon, [CoreBndr], MatchResult)] -- Alternatives
- -> MatchResult
+mkCoAlgCaseMatchResult
+ :: Id -- Scrutinee
+ -> Type -- Type of exp
+ -> [(DataCon, [CoreBndr], MatchResult)] -- Alternatives (bndrs *include* tyvars, dicts)
+ -> MatchResult
mkCoAlgCaseMatchResult var ty match_alts
| isNewTyCon tycon -- Newtype case; use a let
= ASSERT( null (tail match_alts) && null (tail arg_ids1) )
isPArrFakeAlts [] = panic "DsUtils: unexpectedly found an empty list of PArr fake alternatives"
--
mk_parrCase fail = do
- lengthP <- dsLookupGlobalId lengthPName
+ lengthP <- dsLookupDPHId lengthPName
alt <- unboxAlt
return (mkWildCase (len lengthP) intTy ty [alt])
where
--
unboxAlt = do
l <- newSysLocalDs intPrimTy
- indexP <- dsLookupGlobalId indexPName
+ indexP <- dsLookupDPHId indexPName
alts <- mapM (mkAlt indexP) sorted_alts
return (DataAlt intDataCon, [l], mkWildCase (Var l) intPrimTy ty (dft : alts))
where
where
case_bndr = case arg1 of
Var v1 | isLocalId v1 -> v1 -- Note [Desugaring seq (2) and (3)]
- _ -> mkWildBinder ty1
+ _ -> mkWildValBinder ty1
mkCoreAppDs fun arg = mkCoreApp fun arg -- The rest is done in MkCore
error_expr <- mkErrorAppDs iRREFUT_PAT_ERROR_ID tuple_ty (ppr pat)
tuple_expr <- matchSimply val_expr PatBindRhs pat local_tuple error_expr
tuple_var <- newSysLocalDs tuple_ty
- let
- mk_tup_bind binder
- = (binder, mkTupleSelector binders binder tuple_var (Var tuple_var))
+ let mk_tup_bind binder
+ = (binder, mkTupleSelector local_binders binder tuple_var (Var tuple_var))
return ( (tuple_var, tuple_expr) : map mk_tup_bind binders )
where
- binders = collectPatBinders pat
- local_tuple = mkBigCoreVarTup binders
- tuple_ty = exprType local_tuple
+ binders = collectPatBinders pat
+ local_binders = map localiseId binders -- See Note [Localise pattern binders]
+ local_tuple = mkBigCoreVarTup binders
+ tuple_ty = exprType local_tuple
mk_bind scrut_var err_var bndr_var = do
-- (mk_bind sv err_var) generates
return (bndr_var, rhs_expr)
where
error_expr = mkCoerce co (Var err_var)
- co = mkUnsafeCoercion (exprType (Var err_var)) (idType bndr_var)
+ co = mkUnsafeCo (exprType (Var err_var)) (idType bndr_var)
is_simple_lpat p = is_simple_pat (unLoc p)
mkVanillaTuplePat :: [OutPat Id] -> Boxity -> Pat Id
-- A vanilla tuple pattern simply gets its type from its sub-patterns
mkVanillaTuplePat pats box
- = TuplePat pats box (mkTupleTy box (length pats) (map hsLPatType pats))
+ = TuplePat pats box (mkTupleTy box (map hsLPatType pats))
-- The Big equivalents for the source tuple expressions
mkBigLHsVarTup :: [Id] -> LHsExpr Id
projects / ghc-hetmet.git / blobdiff