-- This assertion isn't necessarily true. It's permitted
-- to given a redundant context in a type signature (eg (Ord a, Eq a) => ...)
-- and when typechecking instance decls we generate redundant "givens" too.
- -- addAvail avails given avail
- addAvail avails given avail `thenNF_Tc` \av ->
- zonkInst given `thenNF_Tc` \given' ->
- returnNF_Tc av
+ addAvail avails given avail
where
avail = Avail (instToId given) NoRhs []
-- Collect together all the bad guys
bad_guys = non_stds ++ concat std_bads
in
-
-- Disambiguate the ones that look feasible
mapTc disambigGroup std_oks `thenTc` \ binds_ambig ->
unifyTauTy chosen_default_ty (mkTyVarTy tyvar) `thenTc_`
reduceContext (text "disambig" <+> ppr dicts)
try_me [] dicts `thenTc` \ (binds, frees, ambigs) ->
- ASSERT( null frees && null ambigs )
+ WARN( not (null frees && null ambigs), ppr frees $$ ppr ambigs )
warnDefault dicts chosen_default_ty `thenTc_`
returnTc binds
(tidy_env, tidy_dict) = tidyInst emptyTidyEnv dict
warnDefault dicts default_ty
- = doptsTc Opt_WarnTypeDefaults `thenTc` \ warn ->
- if warn then warnTc True msg else returnNF_Tc ()
+ = doptsTc Opt_WarnTypeDefaults `thenTc` \ warn_flag ->
+ if warn_flag
+ then mapNF_Tc warn groups `thenNF_Tc_` returnNF_Tc ()
+ else returnNF_Tc ()
where
- msg | length dicts > 1
- = (ptext SLIT("Defaulting the following constraint(s) to type") <+> quotes (ppr default_ty))
- $$ pprInstsInFull tidy_dicts
- | otherwise
- = ptext SLIT("Defaulting") <+> quotes (pprInst (head tidy_dicts)) <+>
- ptext SLIT("to type") <+> quotes (ppr default_ty)
-
+ -- Tidy them first
(_, tidy_dicts) = mapAccumL tidyInst emptyTidyEnv dicts
+ -- Group the dictionaries by source location
+ groups = equivClasses cmp tidy_dicts
+ i1 `cmp` i2 = get_loc i1 `compare` get_loc i2
+ get_loc i = case instLoc i of { (_,loc,_) -> loc }
+
+ warn [dict] = tcAddSrcLoc (get_loc dict) $
+ warnTc True (ptext SLIT("Defaulting") <+> quotes (pprInst dict) <+>
+ ptext SLIT("to type") <+> quotes (ppr default_ty))
+
+ warn dicts = tcAddSrcLoc (get_loc (head dicts)) $
+ warnTc True (vcat [ptext SLIT("Defaulting the following constraint(s) to type") <+> quotes (ppr default_ty),
+ pprInstsInFull dicts])
+
addTopIPErr dict
= addInstErrTcM (instLoc dict)
(tidy_env,