go build example.net/need117
! go build example.net/bad114
stderr '^bad114[/\\]bad114.go:15:2: duplicate method .?Y.?( .*)?$'


# With a vendor/modules.txt lacking language versions, the world is topsy-turvy,
# because we have to guess a uniform version for everything.
#
# We always guess Go 1.16, because that was the last version for which
# 'go mod vendor' failed to record dependency versions, and it has most of