Ply can crash if SyntaxError is raised inside a production

[PJBaker]

According to the documentation, production rules can signal errors by raising the SyntaxError exception. However when I try this, my program crashes due to an IndexError exception inside Ply.

A simple example:

import ply.lex as lex
import ply.yacc as yacc

tokens = ('A', 'B')

t_A = 'a'
t_B = 'b'

t_ignore = ' \t'

def t_error(t):
    print("Illegal character '%s'" % t.value[0])
    t.lexer.skip(1)

lexer = lex.lex()

def p_foo(p):
    """foo : A B"""
    raise SyntaxError()

def p_error(p):
    print("Syntax error in input!")

parser = yacc.yacc()

print(parser.parse('a b'))

The result of running this code is:

Generating LALR tables
Traceback (most recent call last):
  File "PlyTest3.py", line 26, in <module>
    print(parser.parse('a b'))
  File "<...>\ply\yacc.py", line 331, in parse
    return self.parseopt_notrack(input, lexer, debug, tracking, tokenfunc)
  File "<...>\ply\yacc.py", line 1115, in parseopt_notrack
    state = statestack[-1]
IndexError: list index out of range

Should I be doing something differently when raising an error?

[dabeaz]

Fixed (I hope).