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Diffstat (limited to 'compiler/parser/RdrHsSyn.hs')
| -rw-r--r-- | compiler/parser/RdrHsSyn.hs | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/compiler/parser/RdrHsSyn.hs b/compiler/parser/RdrHsSyn.hs index 357d22438a..6ac6cbc974 100644 --- a/compiler/parser/RdrHsSyn.hs +++ b/compiler/parser/RdrHsSyn.hs @@ -55,6 +55,7 @@ module RdrHsSyn ( checkValSigLhs, checkDoAndIfThenElse, checkRecordSyntax, + checkEmptyGADTs, parseErrorSDoc, hintBangPat, splitTilde, splitTildeApps, @@ -783,6 +784,21 @@ checkRecordSyntax lr@(L loc r) (text "Illegal record syntax (use TraditionalRecordSyntax):" <+> ppr r) +-- | Check if the gadt_constrlist is empty. Only raise parse error for +-- `data T where` to avoid affecting existing error message, see #8258. +checkEmptyGADTs :: Located ([AddAnn], [LConDecl GhcPs]) + -> P (Located ([AddAnn], [LConDecl GhcPs])) +checkEmptyGADTs gadts@(L span (_, [])) -- Empty GADT declaration. + = do opts <- fmap options getPState + if LangExt.GADTSyntax `extopt` opts -- GADTs implies GADTSyntax + then return gadts + else parseErrorSDoc span $ vcat + [ text "Illegal keyword 'where' in data declaration" + , text "Perhaps you intended to use GADTs or a similar language" + , text "extension to enable syntax: data T where" + ] +checkEmptyGADTs gadts = return gadts -- Ordinary GADT declaration. + checkTyClHdr :: Bool -- True <=> class header -- False <=> type header -> LHsType GhcPs |