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Band-Aid: fix one of the left recursion bugs (fixes #1047) #1048

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merged 3 commits into from
Oct 18, 2024
Merged

Band-Aid: fix one of the left recursion bugs (fixes #1047) #1048

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e264d69
Band-Aid: fix one of the left recursion bugs (fixes #1047)
Tartasprint Oct 18, 2024
c93aae8
Forgot formatting
Tartasprint Oct 18, 2024
3ae5eba
Added test for validating left recursion in the case of a sequence st…
Tartasprint Oct 18, 2024
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24 changes: 23 additions & 1 deletion meta/src/validator.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -667,7 +667,13 @@ fn left_recursion<'a, 'i: 'a>(rules: HashMap<String, &'a ParserNode<'i>>) -> Vec
None
}
ParserExpr::Seq(ref lhs, ref rhs) => {
if is_non_failing(&lhs.expr, rules, &mut vec![trace.last().unwrap().clone()]) {
if is_non_failing(&lhs.expr, rules, &mut vec![trace.last().unwrap().clone()])
|| is_non_progressing(
&lhs.expr,
rules,
&mut vec![trace.last().unwrap().clone()],
)
{
check_expr(rhs, rules, trace)
} else {
check_expr(lhs, rules, trace)
Expand Down Expand Up @@ -1811,6 +1817,22 @@ mod tests {
#[test]
#[should_panic(expected = "grammar error

--> 1:14
|
1 | a = { !\"a\" ~ a }
| ^
|
= rule a is left-recursive (a -> a); pest::pratt_parser might be useful in this case")]
fn non_progressing_left_recursion() {
let input = "a = { !\"a\" ~ a }";
unwrap_or_report(consume_rules(
PestParser::parse(Rule::grammar_rules, input).unwrap(),
));
}

#[test]
#[should_panic(expected = "grammar error

--> 1:7
|
1 | a = { \"a\"* | \"a\" | \"b\" }
Expand Down
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