This was an important conflict. In the following expression:
def a: 0; . | a
Bison needs to decide between these two equally valid
parses:
(def a: 0; .) | a
def a: 0; (. | a)
For jq we want the second one, because the first results in
"a/0 is not defined". In the current parser the first parse
is a reduce and the second parse is a shift. Since Bison
prefers to shift in shift/reduce conflicts, we accidentally
got the correct behavior.
This commit adds a precedence level FUNCDEF which is lower
precedence than '|', meaning we explicitly choose the
correct parse.
Of course many unit tests already cover this case, but I
added one specifically for it.
David Tolnay
66ef8e2c24