Input matches rule A, but A|B fails to match

[rhoark]

I'm trying to parse mathematical expressions with operator precedence, but I'm running into an odd problem where a rule of the form "A | B" fails to match, despite the fact that rule A matches the input string.
A stripped-down version of the grammar that exhibits this behavior:

spec = """
integer_literal = < digit+ >:x -> ("integer_literal",x)

oplevel_unary_left = ('+'|'-'):op unit:X -> ("op",1,op,X)
oplevel_unary_and_higher = oplevel_unary_left | integer_literal
oplevel_exponent = oplevel_exponent_and_higher:L ws ('^'):op ws oplevel_unary_and_higher:R -> ("op",2,op,L,R)
oplevel_exponent_and_higher = oplevel_exponent | oplevel_unary_and_higher
oplevel_mult = oplevel_mult_and_higher:L ws ('*'|'/'|'%'):op ws oplevel_exponent_and_higher:R -> ("op",2,op,L,R)
oplevel_mult_and_higher = oplevel_mult | oplevel_exponent_and_higher
"""

parser = parsley.makeGrammar(spec, {})

Then I get

>>> parser("2*3").oplevel_mult()
('op', 2, '*', ('integer_literal', '2'), ('integer_literal', '3'))
but
>>> parser("2*3").oplevel_mult_and_higher()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Program Files\Anaconda3\lib\site-packages\parsley.py", line 98, in invokeRule
    raise err
ometa.runtime.ParseError:
2*3
  ^
Parse error at line 1, column 2: expected EOF. trail: [digit]
(or similarly with exponent_and_higher vs. just exponent)

I don't see how it's even possible for oplevel_mult_and_higher to fail when the first arm is oplevel_mult, which passes.

[wmstack]

is unit supposed to be integer_literal?

[rhoark]

In the larger original code, unit was a literal or a variable name. For the purpose of this example it should have been changed to just a literal. Regardless, the expected behavior should be to never evaluate the right side of the pipe in oplevel_mult_and_higher.

[wmstack]

Yeah, you are right. I arrived here because I had a similar problem.