Unresolved conflict for symbol sequence:

  expression  '+'  expression  •  '*'  …

Possible interpretations:

  1:  (sum  expression  '+'  expression)  •  '*'  …               (precedence: 0, associativity: Left)
  2:  expression  '+'  (other_thing  expression  •  '*'  '*')     (precedence: -1, associativity: Left)
  3:  expression  '+'  (product  expression  •  '*'  expression)  (precedence: 1, associativity: Left)

Possible resolutions:

  1:  Specify a higher precedence in `product` and `other_thing` than in the other rules.
  2:  Specify a higher precedence in `sum` than in the other rules.
  3:  Add a conflict for these rules: `sum`, `product`, `other_thing`