@ -498,7 +498,7 @@ def disambiguate_pattern_names(patterns: Sequence[Pattern],
be displayed. Default displays all warnings.
"""
used_names = []
for pat in patterns:
for pat in set(patterns):
# Shorten names which already exceed max-length
if len(pat.name) > max_name_length:
shortened_name = pat.name[:max_name_length - suffix_length]