def check(rules):
grammar = Grammar(rules, goal_nts=['goal'])
out = io.StringIO()
self.assertRaisesRegex(
ValueError,
r"ambiguous grammar|reduce-reduce conflict",
lambda: gen.generate_parser(out, grammar))
def testAmbiguous(self):
# This grammar should fail verification.
# It's ambiguous: is ABC s(A)y(BC) or s(AB)y(C)?
grammar = Grammar({
'goal': [
['s', 'y'],
],
's': [
['A'],
['s', 'B'],
],
'y': [
['C'],
['B', 'C'],
],
})
out = io.StringIO()
self.assertRaisesRegex(ValueError, r"shift-reduce conflict",
lambda: gen.generate_parser(out, grammar))
