-tidyNPat :: HsOverLit Id -> Maybe (SyntaxExpr Id) -> SyntaxExpr Id -> Pat Id
-tidyNPat (OverLit val False _ ty) mb_neg _
+tidyNPat :: (HsLit -> Pat Id) -- How to tidy a LitPat
+ -- We need this argument because tidyNPat is called
+ -- both by Match and by Check, but they tidy LitPats
+ -- slightly differently; and we must desugar
+ -- literals consistently (see Trac #5117)
+ -> HsOverLit Id -> Maybe (SyntaxExpr Id) -> SyntaxExpr Id
+ -> Pat Id
+tidyNPat tidy_lit_pat (OverLit val False _ ty) mb_neg _