diff options
Diffstat (limited to 'compiler/rename/RnPat.lhs')
| -rw-r--r-- | compiler/rename/RnPat.lhs | 21 |
1 files changed, 16 insertions, 5 deletions
diff --git a/compiler/rename/RnPat.lhs b/compiler/rename/RnPat.lhs index 9738585aa4..a039f36b25 100644 --- a/compiler/rename/RnPat.lhs +++ b/compiler/rename/RnPat.lhs @@ -61,6 +61,8 @@ import SrcLoc import FastString import Literal ( inCharRange ) import Control.Monad ( when ) +import TysWiredIn ( nilDataCon ) +import DataCon ( dataConName ) \end{code} @@ -375,11 +377,20 @@ rnPatAndThen mk p@(ViewPat expr pat ty) rnPatAndThen mk (ConPatIn con stuff) -- rnConPatAndThen takes care of reconstructing the pattern - = rnConPatAndThen mk con stuff - -rnPatAndThen mk (ListPat pats _) - = do { pats' <- rnLPatsAndThen mk pats - ; return (ListPat pats' placeHolderType) } + -- The pattern for the empty list needs to be replaced by an empty explicit list pattern when overloaded lists is turned on. + = case unLoc con == nameRdrName (dataConName nilDataCon) of + True -> do { ol_flag <- liftCps $ xoptM Opt_OverloadedLists + ; if ol_flag then rnPatAndThen mk (ListPat [] placeHolderType Nothing) + else rnConPatAndThen mk con stuff} + False -> rnConPatAndThen mk con stuff + +rnPatAndThen mk (ListPat pats _ _) + = do { opt_OverloadedLists <- liftCps $ xoptM Opt_OverloadedLists + ; pats' <- rnLPatsAndThen mk pats + ; case opt_OverloadedLists of + True -> do { (to_list_name,_) <- liftCps $ lookupSyntaxName toListName + ; return (ListPat pats' placeHolderType (Just (placeHolderType, to_list_name)))} + False -> return (ListPat pats' placeHolderType Nothing) } rnPatAndThen mk (PArrPat pats _) = do { pats' <- rnLPatsAndThen mk pats |