#include "HsVersions.h"
-
import Match ( matchWrapper, matchSimply, matchSinglePat )
import MatchLit ( dsLit, dsOverLit )
-import DsBinds ( dsLHsBinds )
+import DsBinds ( dsLHsBinds, dsCoercion )
import DsGRHSs ( dsGuarded )
import DsListComp ( dsListComp, dsPArrComp )
import DsUtils ( mkErrorAppDs, mkStringExpr, mkConsExpr, mkNilExpr,
#endif
import HsSyn
-import TcHsSyn ( hsPatType )
+import TcHsSyn ( hsPatType, mkVanillaTuplePat )
-- NB: The desugarer, which straddles the source and Core worlds, sometimes
-- needs to see source types (newtypes etc), and sometimes not
%************************************************************************
%* *
-\subsection{dsLet}
+ dsLocalBinds, dsValBinds
%* *
%************************************************************************
-@dsLet@ is a match-result transformer, taking the @MatchResult@ for the body
-and transforming it into one for the let-bindings enclosing the body.
-
-This may seem a bit odd, but (source) let bindings can contain unboxed
-binds like
-\begin{verbatim}
- C x# = e
-\end{verbatim}
-This must be transformed to a case expression and, if the type has
-more than one constructor, may fail.
-
\begin{code}
dsLocalBinds :: HsLocalBinds Id -> CoreExpr -> DsM CoreExpr
dsLocalBinds EmptyLocalBinds body = return body
-------------------------
dsValBinds :: HsValBinds Id -> CoreExpr -> DsM CoreExpr
-dsValBinds (ValBindsOut binds) body = foldrDs ds_val_bind body binds
+dsValBinds (ValBindsOut binds _) body = foldrDs ds_val_bind body binds
-------------------------
dsIPBinds (IPBinds ip_binds dict_binds) body
-- We need to do a case right away, rather than building
-- a tuple and doing selections.
-- Silently ignore INLINE and SPECIALISE pragmas...
-ds_val_bind (is_rec, hsbinds) body
+ds_val_bind (NonRecursive, hsbinds) body
| [L _ (AbsBinds [] [] exports binds)] <- bagToList hsbinds,
+ (L loc bind : null_binds) <- bagToList binds,
or [isUnLiftedType (idType g) | (_, g, _, _) <- exports]
- = ASSERT (case is_rec of {NonRecursive -> True; other -> False})
- -- Unlifted bindings are always non-recursive
- -- and are always a Fun or Pat monobind
- --
- -- ToDo: in some bizarre case it's conceivable that there
- -- could be dict binds in the 'binds'. (See the notes
- -- below. Then pattern-match would fail. Urk.)
- let
+ || isBangHsBind bind
+ = let
body_w_exports = foldr bind_export body exports
bind_export (tvs, g, l, _) body = ASSERT( null tvs )
bindNonRec g (Var l) body
-
- mk_error_app pat = mkErrorAppDs iRREFUT_PAT_ERROR_ID
- (exprType body)
- (showSDoc (ppr pat))
in
- case bagToList binds of
- [L loc (FunBind (L _ fun) _ matches _)]
- -> putSrcSpanDs loc $
- matchWrapper (FunRhs (idName fun)) matches `thenDs` \ (args, rhs) ->
+ ASSERT (null null_binds)
+ -- Non-recursive, non-overloaded bindings only come in ones
+ -- ToDo: in some bizarre case it's conceivable that there
+ -- could be dict binds in the 'binds'. (See the notes
+ -- below. Then pattern-match would fail. Urk.)
+ putSrcSpanDs loc $
+ case bind of
+ FunBind { fun_id = L _ fun, fun_matches = matches, fun_co_fn = co_fn }
+ -> matchWrapper (FunRhs (idName fun)) matches `thenDs` \ (args, rhs) ->
ASSERT( null args ) -- Functions aren't lifted
+ ASSERT( isIdCoercion co_fn )
returnDs (bindNonRec fun rhs body_w_exports)
- [L loc (PatBind pat grhss ty _)]
+ PatBind {pat_lhs = pat, pat_rhs = grhss, pat_rhs_ty = ty }
-> putSrcSpanDs loc $
dsGuarded grhss ty `thenDs` \ rhs ->
mk_error_app pat `thenDs` \ error_expr ->
matchSimply rhs PatBindRhs pat body_w_exports error_expr
other -> pprPanic "dsLet: unlifted" (pprLHsBinds hsbinds $$ ppr body)
+ where
+ mk_error_app pat = mkErrorAppDs iRREFUT_PAT_ERROR_ID
+ (exprType body)
+ (showSDoc (ppr pat))
--- Ordinary case for bindings
+-- Ordinary case for bindings; none should be unlifted
ds_val_bind (is_rec, binds) body
- = dsLHsBinds binds `thenDs` \ prs ->
- returnDs (Let (Rec prs) body)
+ = do { prs <- dsLHsBinds binds
+ ; ASSERT( not (any (isUnLiftedType . idType . fst) prs) )
+ case prs of
+ [] -> return body
+ other -> return (Let (Rec prs) body) }
-- Use a Rec regardless of is_rec.
-- Why? Because it allows the binds to be all
-- mixed up, which is what happens in one rare case
returnDs (Note (CoreNote $ unpackFS fs) core_expr)
-- Special case to handle unboxed tuple patterns; they can't appear nested
+-- The idea is that
+-- case e of (# p1, p2 #) -> rhs
+-- should desugar to
+-- case e of (# x1, x2 #) -> ... match p1, p2 ...
+-- NOT
+-- let x = e in case x of ....
+--
+-- But there may be a big
+-- let fail = ... in case e of ...
+-- wrapping the whole case, which complicates matters slightly
+-- It all seems a bit fragile. Test is dsrun013.
+
dsExpr (HsCase discrim matches@(MatchGroup _ ty))
| isUnboxedTupleType (funArgTy ty)
= dsLExpr discrim `thenDs` \ core_discrim ->
matchWrapper CaseAlt matches `thenDs` \ ([discrim_var], matching_code) ->
- case matching_code of
- Case (Var x) bndr ty alts | x == discrim_var ->
- returnDs (Case core_discrim bndr ty alts)
- _ -> panic ("dsLExpr: tuple pattern:\n" ++ showSDoc (ppr matching_code))
+ let
+ scrungle (Case (Var x) bndr ty alts)
+ | x == discrim_var = Case core_discrim bndr ty alts
+ scrungle (Let binds body) = Let binds (scrungle body)
+ scrungle other = panic ("dsLExpr: tuple pattern:\n" ++ showSDoc (ppr other))
+ in
+ returnDs (scrungle matching_code)
dsExpr (HsCase discrim matches)
= dsLExpr discrim `thenDs` \ core_discrim ->
mk_alt con
= newSysLocalsDs (dataConInstOrigArgTys con in_inst_tys) `thenDs` \ arg_ids ->
- -- This call to dataConArgTys won't work for existentials
+ -- This call to dataConInstOrigArgTys won't work for existentials
-- but existentials don't have record types anyway
let
val_args = zipWithEqual "dsExpr:RecordUpd" mk_val_arg
dsExpr (DictApp expr dicts) -- becomes a curried application
= dsLExpr expr `thenDs` \ core_expr ->
returnDs (foldl (\f d -> f `App` (Var d)) core_expr dicts)
+
+dsExpr (HsCoerce co_fn e) = dsCoercion co_fn (dsExpr e)
\end{code}
Here is where we desugar the Template Haskell brackets and escapes
go (new_bind_stmt : let_stmt : stmts)
where
new_bind_stmt = mkBindStmt (mk_tup_pat later_pats) mfix_app
- let_stmt = LetStmt (HsValBinds (ValBindsOut [(Recursive, binds)]))
+ let_stmt = LetStmt (HsValBinds (ValBindsOut [(Recursive, binds)] []))
-- Remove the later_ids that appear (without fancy coercions)
mk_tup_pat :: [LPat Id] -> LPat Id
mk_tup_pat [p] = p
- mk_tup_pat ps = noLoc $ TuplePat ps Boxed
+ mk_tup_pat ps = noLoc $ mkVanillaTuplePat ps Boxed
mk_ret_tup :: [LHsExpr Id] -> LHsExpr Id
mk_ret_tup [r] = r
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