Record the type in TuplePat (necessary for GADTs)

[ghc-hetmet.git] / ghc / compiler / deSugar / DsExpr.lhs

diff --git a/ghc/compiler/deSugar/DsExpr.lhs b/ghc/compiler/deSugar/DsExpr.lhs
index ce5a9d8..164316c 100644 (file)
--- a/ghc/compiler/deSugar/DsExpr.lhs
+++ b/ghc/compiler/deSugar/DsExpr.lhs
@@ -11,7 +11,7 @@ module DsExpr ( dsExpr, dsLExpr, dsLocalBinds, dsValBinds, dsLit ) where
 
 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,
@@ -26,7 +26,7 @@ import DsMeta         ( dsBracket )
 #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
@@ -121,13 +121,14 @@ ds_val_bind (is_rec, hsbinds) body
                                    (showSDoc (ppr pat))
     in
     case bagToList binds of
-      [L loc (FunBind (L _ fun) _ matches _)]
+      [L loc (FunBind { fun_id = L _ fun, fun_matches = matches, fun_co_fn = co_fn })]
        -> putSrcSpanDs loc                                     $
           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 _)]
+      [L loc (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 ->
@@ -257,14 +258,29 @@ dsExpr (HsCoreAnn fs expr)
     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 ->
@@ -548,6 +564,8 @@ dsExpr (DictLam dictvars expr)
 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
@@ -718,7 +736,7 @@ dsMDo tbl stmts body result_ty
 
        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