-
------------------------
-misMatchMsg :: TcType -> TcType -> TcM (TidyEnv, SDoc)
--- Generate the message when two types fail to match,
--- going to some trouble to make it helpful.
--- The argument order is: actual type, expected type
-misMatchMsg ty_act ty_exp
- = do { env0 <- tcInitTidyEnv
- ; (env1, pp_exp, extra_exp) <- ppr_ty env0 ty_exp ty_act
- ; (env2, pp_act, extra_act) <- ppr_ty env1 ty_act ty_exp
- ; return (env2,
- sep [sep [ptext SLIT("Couldn't match expected type") <+> pp_exp,
- nest 7 $
- ptext SLIT("against inferred type") <+> pp_act],
- nest 2 (extra_exp $$ extra_act)]) }
-
-ppr_ty :: TidyEnv -> TcType -> TcType -> TcM (TidyEnv, SDoc, SDoc)
-ppr_ty env ty other_ty
- = do { ty' <- zonkTcType ty
- ; let (env1, tidy_ty) = tidyOpenType env ty'
- ; (env2, extra) <- ppr_extra env1 tidy_ty other_ty
- ; return (env2, quotes (ppr tidy_ty), extra) }
-
--- (ppr_extra env ty other_ty) shows extra info about 'ty'
-ppr_extra env (TyVarTy tv) other_ty
- | isSkolemTyVar tv || isSigTyVar tv
- = return (env1, pprSkolTvBinding tv1)
- where
- (env1, tv1) = tidySkolemTyVar env tv
-
-ppr_extra env (TyConApp tc1 _) (TyConApp tc2 _)
- | getOccName tc1 == getOccName tc2
- = -- This case helps with messages that would otherwise say
- -- Could not match 'T' does not match 'M.T'
- -- which is not helpful
- do { this_mod <- getModule
- ; return (env, quotes (ppr tc1) <+> ptext SLIT("is defined") <+> mk_mod this_mod) }
- where
- tc_mod = nameModule (getName tc1)
- tc_pkg = modulePackageId tc_mod
- tc2_pkg = modulePackageId (nameModule (getName tc2))
- mk_mod this_mod
- | tc_mod == this_mod = ptext SLIT("in this module")
-
- | not home_pkg && tc2_pkg /= tc_pkg = pp_pkg
- -- Suppress the module name if (a) it's from another package
- -- (b) other_ty isn't from that same package
-
- | otherwise = ptext SLIT("in module") <+> quotes (ppr tc_mod) <+> pp_pkg
- where
- home_pkg = tc_pkg == modulePackageId this_mod
- pp_pkg | home_pkg = empty
- | otherwise = ptext SLIT("in package") <+> quotes (ppr tc_pkg)
-
-ppr_extra env ty other_ty = return (env, empty) -- Normal case