Commit ce673b2b authored by dterei's avatar dterei

SafeHaskell: Fix bug with overlapping instances reporting wrong error

parent 5f96d5b2
......@@ -21,7 +21,6 @@ module InstEnv (
#include "HsVersions.h"
import DynFlags
import Class
import Var
import VarSet
......@@ -462,9 +461,9 @@ lookupInstEnv (pkg_ie, home_ie) cls tys
all_matches = home_matches ++ pkg_matches
all_unifs = home_unifs ++ pkg_unifs
pruned_matches = foldr insert_overlapping [] all_matches
(safe_matches, safe_fail) = if length pruned_matches /= 1
then (pruned_matches, False)
else check_safe (head pruned_matches) all_matches
(safe_matches, safe_fail) = if length pruned_matches == 1
then check_safe (head pruned_matches) all_matches
else (pruned_matches, False)
-- Even if the unifs is non-empty (an error situation)
-- we still prune the matches, so that the error message isn't
-- misleading (complaining of multiple matches when some should be
......@@ -481,7 +480,7 @@ lookupInstEnv (pkg_ie, home_ie) cls tys
check_safe match@(inst,_) others
= case isSafeOverlap (is_flag inst) of
-- most specific isn't from a Safe module so OK
False -> ([match], True)
False -> ([match], False)
-- otherwise we make sure it only overlaps instances from
-- the same module
True -> (go [] others, True)
......
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