Should not allow left recursion grammar to pass conversion

[cch123]

eg:

{
//------ start
package main

func main() {
    if len(os.Args) != 2 {
        log.Fatal("Usage: calculator 'EXPR'")
    }
    got, err := ParseReader("", strings.NewReader(os.Args[1]))
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("%#v\n", got)
}

// ------ end
}

Input <- expr:Expr EOF {
    return expr, nil
}

Expr <- _ Expr _ LogicOp _ Expr _/ _ Value _

LogicOp <- ("and" / "or") {
    return string(c.text), nil
}

Value <- [0-9]+ {
    return string(c.text),nil
}

_ "whitespace" <- [ \n\t\r]*

EOF <- !.

go run main.go "1 and 1"

Will cause dead loop

[breml]

Not sure, how we could detect this in a reliable way.
@cch123 if you have an idea, feel free to share.

[cch123]

Maybe a simple idea is like detecting a cycle in a dag,
start from the rule root, push every left rule to its map, until every rule is traversed.
eg:

expr <- AX / B
A <- Z / C

make a map to record every left rule:
[expr] -> add A
[expr A] -> add B
[expr A B] -> add Child of A 1 -> add Z
[expr A B Z] -> add Child of A 2 -> add C
[expr A B Z C] -> finish, there are no cycles

expr <- AX / B
A <- expr / C

[expr] -> add A
[expr A] -> add B
[expr A B] -> add Child of A 1 -> add expr -> there is already a expr in map, so it's left recursion~

https://github.com/pest-parser/pest/blob/master/meta/src/validator.rs#L727, perhaps this can provide more ideas

[breml]

@cch123 I am not sure, if you still follow this issue, since it has been several years since you raised it. But in #123 we have a PR, that fixes this issue and it would be great, if you could give it a try and report back whether it works for you or not. Thanks.

[cch123]

code in master branch will cause a stack overflow

~/pigeon ❯❯❯ go run main.go "1 and 1"
runtime: goroutine stack exceeds 1000000000-byte limit
runtime: sp=0x140200e0350 stack=[0x140200e0000, 0x140400e0000]
fatal error: stack overflow

runtime stack:
runtime.throw({0x100a26f59?, 0x100ad9fe0?})
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/panic.go:1047 +0x40 fp=0x16f58ad20 sp=0x16f58acf0 pc=0x1009b8780
runtime.newstack()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/stack.go:1105 +0x468 fp=0x16f58aed0 sp=0x16f58ad20 pc=0x1009d0ee8
runtime.morestack()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:316 +0x70 fp=0x16f58aed0 sp=0x16f58aed0 pc=0x1009e3d00

goroutine 1 [running]:
runtime.writeHeapBits.write({0x14005d2d000?, 0x0?, 0x34?, 0x34?}, 0x2c?, 0x6?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mbitmap.go:791 +0x13c fp=0x140200e0350 sp=0x140200e0350 pc=0x10099a00c
runtime.heapBitsSetType(0x14005d2d1a0, 0x30, 0x30, 0x100a5ff80)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mbitmap.go:1026 +0xd4 fp=0x140200e0410 sp=0x140200e0350 pc=0x10099a3b4
runtime.mallocgc(0x30, 0x100a5ff80, 0x1)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/malloc.go:1074 +0x5a4 fp=0x140200e0480 sp=0x140200e0410 pc=0x100992f14
runtime.newobject(0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/malloc.go:1254 +0x2c fp=0x140200e04b0 sp=0x140200e0480 pc=0x10099337c
runtime.makemap_small()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/map.go:294 +0x24 fp=0x140200e04e0 sp=0x140200e04b0 pc=0x100993f64
main.(*parser).pushV(...)
	/Users/xargin/pigeon/main.go:734
main.(*parser).parseZeroOrMoreExpr(0x140000bc000, 0x100ae7200)
	/Users/xargin/pigeon/main.go:1484 +0x1cc fp=0x140200e05a0 sp=0x140200e04e0 pc=0x100a23fec
main.(*parser).parseExpr(0x140000bc000, {0x100a4e0a0?, 0x100ae7200?})
	/Users/xargin/pigeon/main.go:1115 +0x4fc fp=0x140200e0790 sp=0x140200e05a0 pc=0x100a1f5dc
main.(*parser).parseRule(0x140000bc000, 0x100aeb360)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e0a10 sp=0x140200e0790 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f40)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e0ac0 sp=0x140200e0a10 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f40?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e0cb0 sp=0x140200e0ac0 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e0dc0 sp=0x140200e0cb0 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e0fb0 sp=0x140200e0dc0 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e1090 sp=0x140200e0fb0 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e1280 sp=0x140200e1090 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e1500 sp=0x140200e1280 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e15b0 sp=0x140200e1500 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e17a0 sp=0x140200e15b0 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e18b0 sp=0x140200e17a0 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e1aa0 sp=0x140200e18b0 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e1b80 sp=0x140200e1aa0 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e1d70 sp=0x140200e1b80 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e1ff0 sp=0x140200e1d70 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e20a0 sp=0x140200e1ff0 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e2290 sp=0x140200e20a0 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e23a0 sp=0x140200e2290 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e2590 sp=0x140200e23a0 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e2670 sp=0x140200e2590 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e2860 sp=0x140200e2670 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e2ae0 sp=0x140200e2860 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e2b90 sp=0x140200e2ae0 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e2d80 sp=0x140200e2b90 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e2e90 sp=0x140200e2d80 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e3080 sp=0x140200e2e90 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e3160 sp=0x140200e3080 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e3350 sp=0x140200e3160 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e35d0 sp=0x140200e3350 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e3680 sp=0x140200e35d0 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e3870 sp=0x140200e3680 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e3980 sp=0x140200e3870 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e3b70 sp=0x140200e3980 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e3c50 sp=0x140200e3b70 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e3e40 sp=0x140200e3c50 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e40c0 sp=0x140200e3e40 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e4170 sp=0x140200e40c0 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e4360 sp=0x140200e4170 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e4470 sp=0x140200e4360 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e4660 sp=0x140200e4470 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e4740 sp=0x140200e4660 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e4930 sp=0x140200e4740 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e4bb0 sp=0x140200e4930 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e4c60 sp=0x140200e4bb0 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e4e50 sp=0x140200e4c60 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e4f60 sp=0x140200e4e50 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e5150 sp=0x140200e4f60 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e5230 sp=0x140200e5150 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e5420 sp=0x140200e5230 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e56a0 sp=0x140200e5420 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e5750 sp=0x140200e56a0 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e5940 sp=0x140200e5750 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e5a50 sp=0x140200e5940 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e5c40 sp=0x140200e5a50 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e5d20 sp=0x140200e5c40 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e5f10 sp=0x140200e5d20 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e6190 sp=0x140200e5f10 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e6240 sp=0x140200e6190 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e6430 sp=0x140200e6240 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e6540 sp=0x140200e6430 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e6730 sp=0x140200e6540 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e6810 sp=0x140200e6730 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e6a00 sp=0x140200e6810 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e6c80 sp=0x140200e6a00 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e6d30 sp=0x140200e6c80 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e6f20 sp=0x140200e6d30 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e7030 sp=0x140200e6f20 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e7220 sp=0x140200e7030 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e7300 sp=0x140200e7220 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e74f0 sp=0x140200e7300 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e7770 sp=0x140200e74f0 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e7820 sp=0x140200e7770 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e7a10 sp=0x140200e7820 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e7b20 sp=0x140200e7a10 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e7d10 sp=0x140200e7b20 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e7df0 sp=0x140200e7d10 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e7fe0 sp=0x140200e7df0 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e8260 sp=0x140200e7fe0 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e8310 sp=0x140200e8260 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e8500 sp=0x140200e8310 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e8610 sp=0x140200e8500 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e8800 sp=0x140200e8610 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e88e0 sp=0x140200e8800 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e8ad0 sp=0x140200e88e0 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e8d50 sp=0x140200e8ad0 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e8e00 sp=0x140200e8d50 pc=0x100a234f8
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfa0?, 0x100ae6f80?})
	/Users/xargin/pigeon/main.go:1107 +0x334 fp=0x140200e8ff0 sp=0x140200e8e00 pc=0x100a1f414
main.(*parser).parseSeqExpr(0x140000bc000, 0x100ae7400)
	/Users/xargin/pigeon/main.go:1437 +0x140 fp=0x140200e9100 sp=0x140200e8ff0 pc=0x100a23830
main.(*parser).parseExpr(0x140000bc000, {0x100a4dfe0?, 0x100ae7400?})
	/Users/xargin/pigeon/main.go:1109 +0x420 fp=0x140200e92f0 sp=0x140200e9100 pc=0x100a1f500
main.(*parser).parseChoiceExpr(0x140000bc000, 0x100ae73c0)
	/Users/xargin/pigeon/main.go:1293 +0x234 fp=0x140200e93d0 sp=0x140200e92f0 pc=0x100a219e4
main.(*parser).parseExpr(0x140000bc000, {0x100a4dd60?, 0x100ae73c0?})
	/Users/xargin/pigeon/main.go:1093 +0x4d0 fp=0x140200e95c0 sp=0x140200e93d0 pc=0x100a1f5b0
main.(*parser).parseRule(0x140000bc000, 0x100aeb420)
	/Users/xargin/pigeon/main.go:1049 +0x488 fp=0x140200e9840 sp=0x140200e95c0 pc=0x100a1ec78
main.(*parser).parseRuleRefExpr(0x140000bc000, 0x100ae6f80)
	/Users/xargin/pigeon/main.go:1424 +0xd8 fp=0x140200e98f0 sp=0x140200e9840 pc=0x100a234f8

goroutine 2 [force gc (idle)]:
runtime.gopark(0x0?, 0x0?, 0x0?, 0x0?, 0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000044fa0 sp=0x14000044f80 pc=0x1009bb1f4
runtime.goparkunlock(...)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:387
runtime.forcegchelper()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:305 +0xb8 fp=0x14000044fd0 sp=0x14000044fa0 pc=0x1009bb038
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x14000044fd0 sp=0x14000044fd0 pc=0x1009e6094
created by runtime.init.6
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:293 +0x24

goroutine 3 [GC sweep wait]:
runtime.gopark(0x1?, 0x0?, 0x0?, 0x0?, 0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000045760 sp=0x14000045740 pc=0x1009bb1f4
runtime.goparkunlock(...)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:387
runtime.bgsweep(0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgcsweep.go:319 +0x110 fp=0x140000457b0 sp=0x14000045760 pc=0x1009a8be0
runtime.gcenable.func1()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:178 +0x28 fp=0x140000457d0 sp=0x140000457b0 pc=0x10099d928
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x140000457d0 sp=0x140000457d0 pc=0x1009e6094
created by runtime.gcenable
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:178 +0x74

goroutine 4 [sleep]:
runtime.gopark(0x14000066000?, 0x74e2ff4f0909?, 0x0?, 0x0?, 0x100a65de8?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000045f00 sp=0x14000045ee0 pc=0x1009bb1f4
runtime.goparkunlock(...)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:387
runtime.(*scavengerState).sleep(0x100aeed20, 0x412e892000000000)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgcscavenge.go:479 +0x128 fp=0x14000045f80 sp=0x14000045f00 pc=0x1009a6bf8
runtime.bgscavenge(0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgcscavenge.go:637 +0x9c fp=0x14000045fb0 sp=0x14000045f80 pc=0x1009a6fcc
runtime.gcenable.func2()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:179 +0x28 fp=0x14000045fd0 sp=0x14000045fb0 pc=0x10099d8c8
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x14000045fd0 sp=0x14000045fd0 pc=0x1009e6094
created by runtime.gcenable
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:179 +0xb8

goroutine 17 [finalizer wait]:
runtime.gopark(0x140000445a8?, 0x6000010099b818?, 0x68?, 0x58?, 0x1?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000044580 sp=0x14000044560 pc=0x1009bb1f4
runtime.runfinq()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mfinal.go:193 +0x10c fp=0x140000447d0 sp=0x14000044580 pc=0x10099c9bc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x140000447d0 sp=0x140000447d0 pc=0x1009e6094
created by runtime.createfing
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mfinal.go:163 +0x84

goroutine 18 [GC worker (idle)]:
runtime.gopark(0x74e2994f9be0?, 0x1?, 0xe3?, 0xdb?, 0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000040740 sp=0x14000040720 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x140000407d0 sp=0x14000040740 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x140000407d0 sp=0x140000407d0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28

goroutine 19 [GC worker (idle)]:
runtime.gopark(0x74e299505690?, 0x3?, 0x87?, 0x15?, 0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000040f40 sp=0x14000040f20 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x14000040fd0 sp=0x14000040f40 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x14000040fd0 sp=0x14000040fd0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28

goroutine 5 [GC worker (idle)]:
runtime.gopark(0x100b22fc0?, 0x3?, 0x1?, 0xde?, 0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000046740 sp=0x14000046720 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x140000467d0 sp=0x14000046740 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x140000467d0 sp=0x140000467d0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28

goroutine 33 [GC worker (idle)]:
runtime.gopark(0x100b22fc0?, 0x3?, 0x11?, 0x75?, 0x4?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000448740 sp=0x14000448720 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x140004487d0 sp=0x14000448740 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x140004487d0 sp=0x140004487d0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28

goroutine 20 [GC worker (idle)]:
runtime.gopark(0x74e299505a4e?, 0x3?, 0x5e?, 0x7?, 0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000041740 sp=0x14000041720 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x140000417d0 sp=0x14000041740 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x140000417d0 sp=0x140000417d0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28

goroutine 34 [GC worker (idle)]:
runtime.gopark(0x74e2994e708f?, 0x3?, 0x15?, 0x27?, 0x100a5ff80?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000448f40 sp=0x14000448f20 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x14000448fd0 sp=0x14000448f40 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x14000448fd0 sp=0x14000448fd0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28

goroutine 35 [GC worker (idle)]:
runtime.gopark(0x74e299501c9e?, 0x3?, 0xc4?, 0xfc?, 0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000449740 sp=0x14000449720 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x140004497d0 sp=0x14000449740 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x140004497d0 sp=0x140004497d0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28

goroutine 36 [GC worker (idle)]:
runtime.gopark(0x74e2994ee1ad?, 0x1?, 0xe7?, 0x18?, 0x100a564c0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000449f40 sp=0x14000449f20 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x14000449fd0 sp=0x14000449f40 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x14000449fd0 sp=0x14000449fd0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28

goroutine 21 [GC worker (idle)]:
runtime.gopark(0x74e2994f89f9?, 0x3?, 0x29?, 0x7?, 0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000041f40 sp=0x14000041f20 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x14000041fd0 sp=0x14000041f40 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x14000041fd0 sp=0x14000041fd0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28

goroutine 37 [GC worker (idle)]:
runtime.gopark(0x74e2994ed76c?, 0x3?, 0x1b?, 0x87?, 0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x1400044a740 sp=0x1400044a720 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x1400044a7d0 sp=0x1400044a740 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x1400044a7d0 sp=0x1400044a7d0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28

goroutine 38 [GC worker (idle)]:
runtime.gopark(0x74e2994e652a?, 0x3?, 0xf4?, 0x8?, 0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x1400044af40 sp=0x1400044af20 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x1400044afd0 sp=0x1400044af40 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x1400044afd0 sp=0x1400044afd0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28

goroutine 6 [GC worker (idle)]:
runtime.gopark(0x74e2994ea7bc?, 0x3?, 0xca?, 0x8?, 0x0?)
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/proc.go:381 +0xe4 fp=0x14000046f40 sp=0x14000046f20 pc=0x1009bb1f4
runtime.gcBgMarkWorker()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1275 +0xec fp=0x14000046fd0 sp=0x14000046f40 pc=0x10099f5dc
runtime.goexit()
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/asm_arm64.s:1172 +0x4 fp=0x14000046fd0 sp=0x14000046fd0 pc=0x1009e6094
created by runtime.gcBgMarkStartWorkers
	/opt/homebrew/Cellar/go/1.20.5/libexec/src/runtime/mgc.go:1199 +0x28
exit status 2

generated main.go

// Code generated by pigeon; DO NOT EDIT.

// ------ start
package main

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"log"
	"math"
	"os"
	"sort"
	"strconv"
	"strings"
	"sync"
	"unicode"
	"unicode/utf8"
)

func main() {
	if len(os.Args) != 2 {
		log.Fatal("Usage: calculator 'EXPR'")
	}
	got, err := ParseReader("", strings.NewReader(os.Args[1]))
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("%#v\n", got)
}

// ------ end

var g = &grammar{
	rules: []*rule{
		{
			name: "Input",
			pos:  position{line: 19, col: 1, offset: 285},
			expr: &actionExpr{
				pos: position{line: 19, col: 10, offset: 294},
				run: (*parser).callonInput1,
				expr: &seqExpr{
					pos: position{line: 19, col: 10, offset: 294},
					exprs: []any{
						&labeledExpr{
							pos:   position{line: 19, col: 10, offset: 294},
							label: "expr",
							expr: &ruleRefExpr{
								pos:  position{line: 19, col: 15, offset: 299},
								name: "Expr",
							},
						},
						&ruleRefExpr{
							pos:  position{line: 19, col: 20, offset: 304},
							name: "EOF",
						},
					},
				},
			},
		},
		{
			name: "Expr",
			pos:  position{line: 23, col: 1, offset: 334},
			expr: &choiceExpr{
				pos: position{line: 23, col: 9, offset: 342},
				alternatives: []any{
					&seqExpr{
						pos: position{line: 23, col: 9, offset: 342},
						exprs: []any{
							&ruleRefExpr{
								pos:  position{line: 23, col: 9, offset: 342},
								name: "_",
							},
							&ruleRefExpr{
								pos:  position{line: 23, col: 11, offset: 344},
								name: "Expr",
							},
							&ruleRefExpr{
								pos:  position{line: 23, col: 16, offset: 349},
								name: "_",
							},
							&ruleRefExpr{
								pos:  position{line: 23, col: 18, offset: 351},
								name: "LogicOp",
							},
							&ruleRefExpr{
								pos:  position{line: 23, col: 26, offset: 359},
								name: "_",
							},
							&ruleRefExpr{
								pos:  position{line: 23, col: 28, offset: 361},
								name: "Expr",
							},
							&ruleRefExpr{
								pos:  position{line: 23, col: 33, offset: 366},
								name: "_",
							},
						},
					},
					&seqExpr{
						pos: position{line: 23, col: 36, offset: 369},
						exprs: []any{
							&ruleRefExpr{
								pos:  position{line: 23, col: 36, offset: 369},
								name: "_",
							},
							&ruleRefExpr{
								pos:  position{line: 23, col: 38, offset: 371},
								name: "Value",
							},
							&ruleRefExpr{
								pos:  position{line: 23, col: 44, offset: 377},
								name: "_",
							},
						},
					},
				},
			},
		},
		{
			name: "LogicOp",
			pos:  position{line: 25, col: 1, offset: 380},
			expr: &actionExpr{
				pos: position{line: 25, col: 12, offset: 391},
				run: (*parser).callonLogicOp1,
				expr: &choiceExpr{
					pos: position{line: 25, col: 13, offset: 392},
					alternatives: []any{
						&litMatcher{
							pos:        position{line: 25, col: 13, offset: 392},
							val:        "and",
							ignoreCase: false,
							want:       "\"and\"",
						},
						&litMatcher{
							pos:        position{line: 25, col: 21, offset: 400},
							val:        "or",
							ignoreCase: false,
							want:       "\"or\"",
						},
					},
				},
			},
		},
		{
			name: "Value",
			pos:  position{line: 29, col: 1, offset: 442},
			expr: &actionExpr{
				pos: position{line: 29, col: 10, offset: 451},
				run: (*parser).callonValue1,
				expr: &oneOrMoreExpr{
					pos: position{line: 29, col: 10, offset: 451},
					expr: &charClassMatcher{
						pos:        position{line: 29, col: 10, offset: 451},
						val:        "[0-9]",
						ranges:     []rune{'0', '9'},
						ignoreCase: false,
						inverted:   false,
					},
				},
			},
		},
		{
			name:        "_",
			displayName: "\"whitespace\"",
			pos:         position{line: 33, col: 1, offset: 493},
			expr: &zeroOrMoreExpr{
				pos: position{line: 33, col: 19, offset: 511},
				expr: &charClassMatcher{
					pos:        position{line: 33, col: 19, offset: 511},
					val:        "[ \\n\\t\\r]",
					chars:      []rune{' ', '\n', '\t', '\r'},
					ignoreCase: false,
					inverted:   false,
				},
			},
		},
		{
			name: "EOF",
			pos:  position{line: 35, col: 1, offset: 523},
			expr: &notExpr{
				pos: position{line: 35, col: 8, offset: 530},
				expr: &anyMatcher{
					line: 35, col: 9, offset: 531,
				},
			},
		},
	},
}

func (c *current) onInput1(expr any) (any, error) {
	return expr, nil
}

func (p *parser) callonInput1() (any, error) {
	stack := p.vstack[len(p.vstack)-1]
	_ = stack
	return p.cur.onInput1(stack["expr"])
}

func (c *current) onLogicOp1() (any, error) {
	return string(c.text), nil
}

func (p *parser) callonLogicOp1() (any, error) {
	stack := p.vstack[len(p.vstack)-1]
	_ = stack
	return p.cur.onLogicOp1()
}

func (c *current) onValue1() (any, error) {
	return string(c.text), nil
}

func (p *parser) callonValue1() (any, error) {
	stack := p.vstack[len(p.vstack)-1]
	_ = stack
	return p.cur.onValue1()
}

var (
	// errNoRule is returned when the grammar to parse has no rule.
	errNoRule = errors.New("grammar has no rule")

	// errInvalidEntrypoint is returned when the specified entrypoint rule
	// does not exit.
	errInvalidEntrypoint = errors.New("invalid entrypoint")

	// errInvalidEncoding is returned when the source is not properly
	// utf8-encoded.
	errInvalidEncoding = errors.New("invalid encoding")

	// errMaxExprCnt is used to signal that the maximum number of
	// expressions have been parsed.
	errMaxExprCnt = errors.New("max number of expresssions parsed")
)

// Option is a function that can set an option on the parser. It returns
// the previous setting as an Option.
type Option func(*parser) Option

// MaxExpressions creates an Option to stop parsing after the provided
// number of expressions have been parsed, if the value is 0 then the parser will
// parse for as many steps as needed (possibly an infinite number).
//
// The default for maxExprCnt is 0.
func MaxExpressions(maxExprCnt uint64) Option {
	return func(p *parser) Option {
		oldMaxExprCnt := p.maxExprCnt
		p.maxExprCnt = maxExprCnt
		return MaxExpressions(oldMaxExprCnt)
	}
}

// Entrypoint creates an Option to set the rule name to use as entrypoint.
// The rule name must have been specified in the -alternate-entrypoints
// if generating the parser with the -optimize-grammar flag, otherwise
// it may have been optimized out. Passing an empty string sets the
// entrypoint to the first rule in the grammar.
//
// The default is to start parsing at the first rule in the grammar.
func Entrypoint(ruleName string) Option {
	return func(p *parser) Option {
		oldEntrypoint := p.entrypoint
		p.entrypoint = ruleName
		if ruleName == "" {
			p.entrypoint = g.rules[0].name
		}
		return Entrypoint(oldEntrypoint)
	}
}

// Statistics adds a user provided Stats struct to the parser to allow
// the user to process the results after the parsing has finished.
// Also the key for the "no match" counter is set.
//
// Example usage:
//
//	input := "input"
//	stats := Stats{}
//	_, err := Parse("input-file", []byte(input), Statistics(&stats, "no match"))
//	if err != nil {
//	    log.Panicln(err)
//	}
//	b, err := json.MarshalIndent(stats.ChoiceAltCnt, "", "  ")
//	if err != nil {
//	    log.Panicln(err)
//	}
//	fmt.Println(string(b))
func Statistics(stats *Stats, choiceNoMatch string) Option {
	return func(p *parser) Option {
		oldStats := p.Stats
		p.Stats = stats
		oldChoiceNoMatch := p.choiceNoMatch
		p.choiceNoMatch = choiceNoMatch
		if p.Stats.ChoiceAltCnt == nil {
			p.Stats.ChoiceAltCnt = make(map[string]map[string]int)
		}
		return Statistics(oldStats, oldChoiceNoMatch)
	}
}

// Debug creates an Option to set the debug flag to b. When set to true,
// debugging information is printed to stdout while parsing.
//
// The default is false.
func Debug(b bool) Option {
	return func(p *parser) Option {
		old := p.debug
		p.debug = b
		return Debug(old)
	}
}

// Memoize creates an Option to set the memoize flag to b. When set to true,
// the parser will cache all results so each expression is evaluated only
// once. This guarantees linear parsing time even for pathological cases,
// at the expense of more memory and slower times for typical cases.
//
// The default is false.
func Memoize(b bool) Option {
	return func(p *parser) Option {
		old := p.memoize
		p.memoize = b
		return Memoize(old)
	}
}

// AllowInvalidUTF8 creates an Option to allow invalid UTF-8 bytes.
// Every invalid UTF-8 byte is treated as a utf8.RuneError (U+FFFD)
// by character class matchers and is matched by the any matcher.
// The returned matched value, c.text and c.offset are NOT affected.
//
// The default is false.
func AllowInvalidUTF8(b bool) Option {
	return func(p *parser) Option {
		old := p.allowInvalidUTF8
		p.allowInvalidUTF8 = b
		return AllowInvalidUTF8(old)
	}
}

// Recover creates an Option to set the recover flag to b. When set to
// true, this causes the parser to recover from panics and convert it
// to an error. Setting it to false can be useful while debugging to
// access the full stack trace.
//
// The default is true.
func Recover(b bool) Option {
	return func(p *parser) Option {
		old := p.recover
		p.recover = b
		return Recover(old)
	}
}

// GlobalStore creates an Option to set a key to a certain value in
// the globalStore.
func GlobalStore(key string, value any) Option {
	return func(p *parser) Option {
		old := p.cur.globalStore[key]
		p.cur.globalStore[key] = value
		return GlobalStore(key, old)
	}
}

// InitState creates an Option to set a key to a certain value in
// the global "state" store.
func InitState(key string, value any) Option {
	return func(p *parser) Option {
		old := p.cur.state[key]
		p.cur.state[key] = value
		return InitState(key, old)
	}
}

// ParseFile parses the file identified by filename.
func ParseFile(filename string, opts ...Option) (i any, err error) {
	f, err := os.Open(filename)
	if err != nil {
		return nil, err
	}
	defer func() {
		if closeErr := f.Close(); closeErr != nil {
			err = closeErr
		}
	}()
	return ParseReader(filename, f, opts...)
}

// ParseReader parses the data from r using filename as information in the
// error messages.
func ParseReader(filename string, r io.Reader, opts ...Option) (any, error) {
	b, err := io.ReadAll(r)
	if err != nil {
		return nil, err
	}

	return Parse(filename, b, opts...)
}

// Parse parses the data from b using filename as information in the
// error messages.
func Parse(filename string, b []byte, opts ...Option) (any, error) {
	return newParser(filename, b, opts...).parse(g)
}

// position records a position in the text.
type position struct {
	line, col, offset int
}

func (p position) String() string {
	return strconv.Itoa(p.line) + ":" + strconv.Itoa(p.col) + " [" + strconv.Itoa(p.offset) + "]"
}

// savepoint stores all state required to go back to this point in the
// parser.
type savepoint struct {
	position
	rn rune
	w  int
}

type current struct {
	pos  position // start position of the match
	text []byte   // raw text of the match

	// state is a store for arbitrary key,value pairs that the user wants to be
	// tied to the backtracking of the parser.
	// This is always rolled back if a parsing rule fails.
	state storeDict

	// globalStore is a general store for the user to store arbitrary key-value
	// pairs that they need to manage and that they do not want tied to the
	// backtracking of the parser. This is only modified by the user and never
	// rolled back by the parser. It is always up to the user to keep this in a
	// consistent state.
	globalStore storeDict
}

type storeDict map[string]any

// the AST types...

type grammar struct {
	pos   position
	rules []*rule
}

type rule struct {
	pos         position
	name        string
	displayName string
	expr        any
}

type choiceExpr struct {
	pos          position
	alternatives []any
}

type actionExpr struct {
	pos  position
	expr any
	run  func(*parser) (any, error)
}

type recoveryExpr struct {
	pos          position
	expr         any
	recoverExpr  any
	failureLabel []string
}

type seqExpr struct {
	pos   position
	exprs []any
}

type throwExpr struct {
	pos   position
	label string
}

type labeledExpr struct {
	pos   position
	label string
	expr  any
}

type expr struct {
	pos  position
	expr any
}

type (
	andExpr        expr
	notExpr        expr
	zeroOrOneExpr  expr
	zeroOrMoreExpr expr
	oneOrMoreExpr  expr
)

type ruleRefExpr struct {
	pos  position
	name string
}

type stateCodeExpr struct {
	pos position
	run func(*parser) error
}

type andCodeExpr struct {
	pos position
	run func(*parser) (bool, error)
}

type notCodeExpr struct {
	pos position
	run func(*parser) (bool, error)
}

type litMatcher struct {
	pos        position
	val        string
	ignoreCase bool
	want       string
}

type charClassMatcher struct {
	pos             position
	val             string
	basicLatinChars [128]bool
	chars           []rune
	ranges          []rune
	classes         []*unicode.RangeTable
	ignoreCase      bool
	inverted        bool
}

type anyMatcher position

// errList cumulates the errors found by the parser.
type errList []error

func (e *errList) add(err error) {
	*e = append(*e, err)
}

func (e errList) err() error {
	if len(e) == 0 {
		return nil
	}
	e.dedupe()
	return e
}

func (e *errList) dedupe() {
	var cleaned []error
	set := make(map[string]bool)
	for _, err := range *e {
		if msg := err.Error(); !set[msg] {
			set[msg] = true
			cleaned = append(cleaned, err)
		}
	}
	*e = cleaned
}

func (e errList) Error() string {
	switch len(e) {
	case 0:
		return ""
	case 1:
		return e[0].Error()
	default:
		var buf bytes.Buffer

		for i, err := range e {
			if i > 0 {
				buf.WriteRune('\n')
			}
			buf.WriteString(err.Error())
		}
		return buf.String()
	}
}

// parserError wraps an error with a prefix indicating the rule in which
// the error occurred. The original error is stored in the Inner field.
type parserError struct {
	Inner    error
	pos      position
	prefix   string
	expected []string
}

// Error returns the error message.
func (p *parserError) Error() string {
	return p.prefix + ": " + p.Inner.Error()
}

// newParser creates a parser with the specified input source and options.
func newParser(filename string, b []byte, opts ...Option) *parser {
	stats := Stats{
		ChoiceAltCnt: make(map[string]map[string]int),
	}

	p := &parser{
		filename: filename,
		errs:     new(errList),
		data:     b,
		pt:       savepoint{position: position{line: 1}},
		recover:  true,
		cur: current{
			state:       make(storeDict),
			globalStore: make(storeDict),
		},
		maxFailPos:      position{col: 1, line: 1},
		maxFailExpected: make([]string, 0, 20),
		Stats:           &stats,
		// start rule is rule [0] unless an alternate entrypoint is specified
		entrypoint: g.rules[0].name,
	}
	p.setOptions(opts)

	if p.maxExprCnt == 0 {
		p.maxExprCnt = math.MaxUint64
	}

	return p
}

// setOptions applies the options to the parser.
func (p *parser) setOptions(opts []Option) {
	for _, opt := range opts {
		opt(p)
	}
}

type resultTuple struct {
	v   any
	b   bool
	end savepoint
}

const choiceNoMatch = -1

// Stats stores some statistics, gathered during parsing
type Stats struct {
	// ExprCnt counts the number of expressions processed during parsing
	// This value is compared to the maximum number of expressions allowed
	// (set by the MaxExpressions option).
	ExprCnt uint64

	// ChoiceAltCnt is used to count for each ordered choice expression,
	// which alternative is used how may times.
	// These numbers allow to optimize the order of the ordered choice expression
	// to increase the performance of the parser
	//
	// The outer key of ChoiceAltCnt is composed of the name of the rule as well
	// as the line and the column of the ordered choice.
	// The inner key of ChoiceAltCnt is the number (one-based) of the matching alternative.
	// For each alternative the number of matches are counted. If an ordered choice does not
	// match, a special counter is incremented. The name of this counter is set with
	// the parser option Statistics.
	// For an alternative to be included in ChoiceAltCnt, it has to match at least once.
	ChoiceAltCnt map[string]map[string]int
}

type parser struct {
	filename string
	pt       savepoint
	cur      current

	data []byte
	errs *errList

	depth   int
	recover bool
	debug   bool

	memoize bool
	// memoization table for the packrat algorithm:
	// map[offset in source] map[expression or rule] {value, match}
	memo map[int]map[any]resultTuple

	// rules table, maps the rule identifier to the rule node
	rules map[string]*rule
	// variables stack, map of label to value
	vstack []map[string]any
	// rule stack, allows identification of the current rule in errors
	rstack []*rule

	// parse fail
	maxFailPos            position
	maxFailExpected       []string
	maxFailInvertExpected bool

	// max number of expressions to be parsed
	maxExprCnt uint64
	// entrypoint for the parser
	entrypoint string

	allowInvalidUTF8 bool

	*Stats

	choiceNoMatch string
	// recovery expression stack, keeps track of the currently available recovery expression, these are traversed in reverse
	recoveryStack []map[string]any
}

// push a variable set on the vstack.
func (p *parser) pushV() {
	if cap(p.vstack) == len(p.vstack) {
		// create new empty slot in the stack
		p.vstack = append(p.vstack, nil)
	} else {
		// slice to 1 more
		p.vstack = p.vstack[:len(p.vstack)+1]
	}

	// get the last args set
	m := p.vstack[len(p.vstack)-1]
	if m != nil && len(m) == 0 {
		// empty map, all good
		return
	}

	m = make(map[string]any)
	p.vstack[len(p.vstack)-1] = m
}

// pop a variable set from the vstack.
func (p *parser) popV() {
	// if the map is not empty, clear it
	m := p.vstack[len(p.vstack)-1]
	if len(m) > 0 {
		// GC that map
		p.vstack[len(p.vstack)-1] = nil
	}
	p.vstack = p.vstack[:len(p.vstack)-1]
}

// push a recovery expression with its labels to the recoveryStack
func (p *parser) pushRecovery(labels []string, expr any) {
	if cap(p.recoveryStack) == len(p.recoveryStack) {
		// create new empty slot in the stack
		p.recoveryStack = append(p.recoveryStack, nil)
	} else {
		// slice to 1 more
		p.recoveryStack = p.recoveryStack[:len(p.recoveryStack)+1]
	}

	m := make(map[string]any, len(labels))
	for _, fl := range labels {
		m[fl] = expr
	}
	p.recoveryStack[len(p.recoveryStack)-1] = m
}

// pop a recovery expression from the recoveryStack
func (p *parser) popRecovery() {
	// GC that map
	p.recoveryStack[len(p.recoveryStack)-1] = nil

	p.recoveryStack = p.recoveryStack[:len(p.recoveryStack)-1]
}

func (p *parser) print(prefix, s string) string {
	if !p.debug {
		return s
	}

	fmt.Printf("%s %d:%d:%d: %s [%#U]\n",
		prefix, p.pt.line, p.pt.col, p.pt.offset, s, p.pt.rn)
	return s
}

func (p *parser) in(s string) string {
	p.depth++
	return p.print(strings.Repeat(" ", p.depth)+">", s)
}

func (p *parser) out(s string) string {
	p.depth--
	return p.print(strings.Repeat(" ", p.depth)+"<", s)
}

func (p *parser) addErr(err error) {
	p.addErrAt(err, p.pt.position, []string{})
}

func (p *parser) addErrAt(err error, pos position, expected []string) {
	var buf bytes.Buffer
	if p.filename != "" {
		buf.WriteString(p.filename)
	}
	if buf.Len() > 0 {
		buf.WriteString(":")
	}
	buf.WriteString(fmt.Sprintf("%d:%d (%d)", pos.line, pos.col, pos.offset))
	if len(p.rstack) > 0 {
		if buf.Len() > 0 {
			buf.WriteString(": ")
		}
		rule := p.rstack[len(p.rstack)-1]
		if rule.displayName != "" {
			buf.WriteString("rule " + rule.displayName)
		} else {
			buf.WriteString("rule " + rule.name)
		}
	}
	pe := &parserError{Inner: err, pos: pos, prefix: buf.String(), expected: expected}
	p.errs.add(pe)
}

func (p *parser) failAt(fail bool, pos position, want string) {
	// process fail if parsing fails and not inverted or parsing succeeds and invert is set
	if fail == p.maxFailInvertExpected {
		if pos.offset < p.maxFailPos.offset {
			return
		}

		if pos.offset > p.maxFailPos.offset {
			p.maxFailPos = pos
			p.maxFailExpected = p.maxFailExpected[:0]
		}

		if p.maxFailInvertExpected {
			want = "!" + want
		}
		p.maxFailExpected = append(p.maxFailExpected, want)
	}
}

// read advances the parser to the next rune.
func (p *parser) read() {
	p.pt.offset += p.pt.w
	rn, n := utf8.DecodeRune(p.data[p.pt.offset:])
	p.pt.rn = rn
	p.pt.w = n
	p.pt.col++
	if rn == '\n' {
		p.pt.line++
		p.pt.col = 0
	}

	if rn == utf8.RuneError && n == 1 { // see utf8.DecodeRune
		if !p.allowInvalidUTF8 {
			p.addErr(errInvalidEncoding)
		}
	}
}

// restore parser position to the savepoint pt.
func (p *parser) restore(pt savepoint) {
	if p.debug {
		defer p.out(p.in("restore"))
	}
	if pt.offset == p.pt.offset {
		return
	}
	p.pt = pt
}

// Cloner is implemented by any value that has a Clone method, which returns a
// copy of the value. This is mainly used for types which are not passed by
// value (e.g map, slice, chan) or structs that contain such types.
//
// This is used in conjunction with the global state feature to create proper
// copies of the state to allow the parser to properly restore the state in
// the case of backtracking.
type Cloner interface {
	Clone() any
}

var statePool = &sync.Pool{
	New: func() any { return make(storeDict) },
}

func (sd storeDict) Discard() {
	for k := range sd {
		delete(sd, k)
	}
	statePool.Put(sd)
}

// clone and return parser current state.
func (p *parser) cloneState() storeDict {
	if p.debug {
		defer p.out(p.in("cloneState"))
	}

	state := statePool.Get().(storeDict)
	for k, v := range p.cur.state {
		if c, ok := v.(Cloner); ok {
			state[k] = c.Clone()
		} else {
			state[k] = v
		}
	}
	return state
}

// restore parser current state to the state storeDict.
// every restoreState should applied only one time for every cloned state
func (p *parser) restoreState(state storeDict) {
	if p.debug {
		defer p.out(p.in("restoreState"))
	}
	p.cur.state.Discard()
	p.cur.state = state
}

// get the slice of bytes from the savepoint start to the current position.
func (p *parser) sliceFrom(start savepoint) []byte {
	return p.data[start.position.offset:p.pt.position.offset]
}

func (p *parser) getMemoized(node any) (resultTuple, bool) {
	if len(p.memo) == 0 {
		return resultTuple{}, false
	}
	m := p.memo[p.pt.offset]
	if len(m) == 0 {
		return resultTuple{}, false
	}
	res, ok := m[node]
	return res, ok
}

func (p *parser) setMemoized(pt savepoint, node any, tuple resultTuple) {
	if p.memo == nil {
		p.memo = make(map[int]map[any]resultTuple)
	}
	m := p.memo[pt.offset]
	if m == nil {
		m = make(map[any]resultTuple)
		p.memo[pt.offset] = m
	}
	m[node] = tuple
}

func (p *parser) buildRulesTable(g *grammar) {
	p.rules = make(map[string]*rule, len(g.rules))
	for _, r := range g.rules {
		p.rules[r.name] = r
	}
}

func (p *parser) parse(g *grammar) (val any, err error) {
	if len(g.rules) == 0 {
		p.addErr(errNoRule)
		return nil, p.errs.err()
	}

	// TODO : not super critical but this could be generated
	p.buildRulesTable(g)

	if p.recover {
		// panic can be used in action code to stop parsing immediately
		// and return the panic as an error.
		defer func() {
			if e := recover(); e != nil {
				if p.debug {
					defer p.out(p.in("panic handler"))
				}
				val = nil
				switch e := e.(type) {
				case error:
					p.addErr(e)
				default:
					p.addErr(fmt.Errorf("%v", e))
				}
				err = p.errs.err()
			}
		}()
	}

	startRule, ok := p.rules[p.entrypoint]
	if !ok {
		p.addErr(errInvalidEntrypoint)
		return nil, p.errs.err()
	}

	p.read() // advance to first rune
	val, ok = p.parseRule(startRule)
	if !ok {
		if len(*p.errs) == 0 {
			// If parsing fails, but no errors have been recorded, the expected values
			// for the farthest parser position are returned as error.
			maxFailExpectedMap := make(map[string]struct{}, len(p.maxFailExpected))
			for _, v := range p.maxFailExpected {
				maxFailExpectedMap[v] = struct{}{}
			}
			expected := make([]string, 0, len(maxFailExpectedMap))
			eof := false
			if _, ok := maxFailExpectedMap["!."]; ok {
				delete(maxFailExpectedMap, "!.")
				eof = true
			}
			for k := range maxFailExpectedMap {
				expected = append(expected, k)
			}
			sort.Strings(expected)
			if eof {
				expected = append(expected, "EOF")
			}
			p.addErrAt(errors.New("no match found, expected: "+listJoin(expected, ", ", "or")), p.maxFailPos, expected)
		}

		return nil, p.errs.err()
	}
	return val, p.errs.err()
}

func listJoin(list []string, sep string, lastSep string) string {
	switch len(list) {
	case 0:
		return ""
	case 1:
		return list[0]
	default:
		return strings.Join(list[:len(list)-1], sep) + " " + lastSep + " " + list[len(list)-1]
	}
}

func (p *parser) parseRule(rule *rule) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseRule " + rule.name))
	}

	if p.memoize {
		res, ok := p.getMemoized(rule)
		if ok {
			p.restore(res.end)
			return res.v, res.b
		}
	}

	start := p.pt
	p.rstack = append(p.rstack, rule)
	p.pushV()
	val, ok := p.parseExpr(rule.expr)
	p.popV()
	p.rstack = p.rstack[:len(p.rstack)-1]
	if ok && p.debug {
		p.print(strings.Repeat(" ", p.depth)+"MATCH", string(p.sliceFrom(start)))
	}

	if p.memoize {
		p.setMemoized(start, rule, resultTuple{val, ok, p.pt})
	}
	return val, ok
}

func (p *parser) parseExpr(expr any) (any, bool) {
	var pt savepoint

	if p.memoize {
		res, ok := p.getMemoized(expr)
		if ok {
			p.restore(res.end)
			return res.v, res.b
		}
		pt = p.pt
	}

	p.ExprCnt++
	if p.ExprCnt > p.maxExprCnt {
		panic(errMaxExprCnt)
	}

	var val any
	var ok bool
	switch expr := expr.(type) {
	case *actionExpr:
		val, ok = p.parseActionExpr(expr)
	case *andCodeExpr:
		val, ok = p.parseAndCodeExpr(expr)
	case *andExpr:
		val, ok = p.parseAndExpr(expr)
	case *anyMatcher:
		val, ok = p.parseAnyMatcher(expr)
	case *charClassMatcher:
		val, ok = p.parseCharClassMatcher(expr)
	case *choiceExpr:
		val, ok = p.parseChoiceExpr(expr)
	case *labeledExpr:
		val, ok = p.parseLabeledExpr(expr)
	case *litMatcher:
		val, ok = p.parseLitMatcher(expr)
	case *notCodeExpr:
		val, ok = p.parseNotCodeExpr(expr)
	case *notExpr:
		val, ok = p.parseNotExpr(expr)
	case *oneOrMoreExpr:
		val, ok = p.parseOneOrMoreExpr(expr)
	case *recoveryExpr:
		val, ok = p.parseRecoveryExpr(expr)
	case *ruleRefExpr:
		val, ok = p.parseRuleRefExpr(expr)
	case *seqExpr:
		val, ok = p.parseSeqExpr(expr)
	case *stateCodeExpr:
		val, ok = p.parseStateCodeExpr(expr)
	case *throwExpr:
		val, ok = p.parseThrowExpr(expr)
	case *zeroOrMoreExpr:
		val, ok = p.parseZeroOrMoreExpr(expr)
	case *zeroOrOneExpr:
		val, ok = p.parseZeroOrOneExpr(expr)
	default:
		panic(fmt.Sprintf("unknown expression type %T", expr))
	}
	if p.memoize {
		p.setMemoized(pt, expr, resultTuple{val, ok, p.pt})
	}
	return val, ok
}

func (p *parser) parseActionExpr(act *actionExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseActionExpr"))
	}

	start := p.pt
	val, ok := p.parseExpr(act.expr)
	if ok {
		p.cur.pos = start.position
		p.cur.text = p.sliceFrom(start)
		state := p.cloneState()
		actVal, err := act.run(p)
		if err != nil {
			p.addErrAt(err, start.position, []string{})
		}
		p.restoreState(state)

		val = actVal
	}
	if ok && p.debug {
		p.print(strings.Repeat(" ", p.depth)+"MATCH", string(p.sliceFrom(start)))
	}
	return val, ok
}

func (p *parser) parseAndCodeExpr(and *andCodeExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseAndCodeExpr"))
	}

	state := p.cloneState()

	ok, err := and.run(p)
	if err != nil {
		p.addErr(err)
	}
	p.restoreState(state)

	return nil, ok
}

func (p *parser) parseAndExpr(and *andExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseAndExpr"))
	}

	pt := p.pt
	state := p.cloneState()
	p.pushV()
	_, ok := p.parseExpr(and.expr)
	p.popV()
	p.restoreState(state)
	p.restore(pt)

	return nil, ok
}

func (p *parser) parseAnyMatcher(any *anyMatcher) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseAnyMatcher"))
	}

	if p.pt.rn == utf8.RuneError && p.pt.w == 0 {
		// EOF - see utf8.DecodeRune
		p.failAt(false, p.pt.position, ".")
		return nil, false
	}
	start := p.pt
	p.read()
	p.failAt(true, start.position, ".")
	return p.sliceFrom(start), true
}

func (p *parser) parseCharClassMatcher(chr *charClassMatcher) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseCharClassMatcher"))
	}

	cur := p.pt.rn
	start := p.pt

	// can't match EOF
	if cur == utf8.RuneError && p.pt.w == 0 { // see utf8.DecodeRune
		p.failAt(false, start.position, chr.val)
		return nil, false
	}

	if chr.ignoreCase {
		cur = unicode.ToLower(cur)
	}

	// try to match in the list of available chars
	for _, rn := range chr.chars {
		if rn == cur {
			if chr.inverted {
				p.failAt(false, start.position, chr.val)
				return nil, false
			}
			p.read()
			p.failAt(true, start.position, chr.val)
			return p.sliceFrom(start), true
		}
	}

	// try to match in the list of ranges
	for i := 0; i < len(chr.ranges); i += 2 {
		if cur >= chr.ranges[i] && cur <= chr.ranges[i+1] {
			if chr.inverted {
				p.failAt(false, start.position, chr.val)
				return nil, false
			}
			p.read()
			p.failAt(true, start.position, chr.val)
			return p.sliceFrom(start), true
		}
	}

	// try to match in the list of Unicode classes
	for _, cl := range chr.classes {
		if unicode.Is(cl, cur) {
			if chr.inverted {
				p.failAt(false, start.position, chr.val)
				return nil, false
			}
			p.read()
			p.failAt(true, start.position, chr.val)
			return p.sliceFrom(start), true
		}
	}

	if chr.inverted {
		p.read()
		p.failAt(true, start.position, chr.val)
		return p.sliceFrom(start), true
	}
	p.failAt(false, start.position, chr.val)
	return nil, false
}

func (p *parser) incChoiceAltCnt(ch *choiceExpr, altI int) {
	choiceIdent := fmt.Sprintf("%s %d:%d", p.rstack[len(p.rstack)-1].name, ch.pos.line, ch.pos.col)
	m := p.ChoiceAltCnt[choiceIdent]
	if m == nil {
		m = make(map[string]int)
		p.ChoiceAltCnt[choiceIdent] = m
	}
	// We increment altI by 1, so the keys do not start at 0
	alt := strconv.Itoa(altI + 1)
	if altI == choiceNoMatch {
		alt = p.choiceNoMatch
	}
	m[alt]++
}

func (p *parser) parseChoiceExpr(ch *choiceExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseChoiceExpr"))
	}

	for altI, alt := range ch.alternatives {
		// dummy assignment to prevent compile error if optimized
		_ = altI

		state := p.cloneState()

		p.pushV()
		val, ok := p.parseExpr(alt)
		p.popV()
		if ok {
			p.incChoiceAltCnt(ch, altI)
			return val, ok
		}
		p.restoreState(state)
	}
	p.incChoiceAltCnt(ch, choiceNoMatch)
	return nil, false
}

func (p *parser) parseLabeledExpr(lab *labeledExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseLabeledExpr"))
	}

	p.pushV()
	val, ok := p.parseExpr(lab.expr)
	p.popV()
	if ok && lab.label != "" {
		m := p.vstack[len(p.vstack)-1]
		m[lab.label] = val
	}
	return val, ok
}

func (p *parser) parseLitMatcher(lit *litMatcher) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseLitMatcher"))
	}

	start := p.pt
	for _, want := range lit.val {
		cur := p.pt.rn
		if lit.ignoreCase {
			cur = unicode.ToLower(cur)
		}
		if cur != want {
			p.failAt(false, start.position, lit.want)
			p.restore(start)
			return nil, false
		}
		p.read()
	}
	p.failAt(true, start.position, lit.want)
	return p.sliceFrom(start), true
}

func (p *parser) parseNotCodeExpr(not *notCodeExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseNotCodeExpr"))
	}

	state := p.cloneState()

	ok, err := not.run(p)
	if err != nil {
		p.addErr(err)
	}
	p.restoreState(state)

	return nil, !ok
}

func (p *parser) parseNotExpr(not *notExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseNotExpr"))
	}

	pt := p.pt
	state := p.cloneState()
	p.pushV()
	p.maxFailInvertExpected = !p.maxFailInvertExpected
	_, ok := p.parseExpr(not.expr)
	p.maxFailInvertExpected = !p.maxFailInvertExpected
	p.popV()
	p.restoreState(state)
	p.restore(pt)

	return nil, !ok
}

func (p *parser) parseOneOrMoreExpr(expr *oneOrMoreExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseOneOrMoreExpr"))
	}

	var vals []any

	for {
		p.pushV()
		val, ok := p.parseExpr(expr.expr)
		p.popV()
		if !ok {
			if len(vals) == 0 {
				// did not match once, no match
				return nil, false
			}
			return vals, true
		}
		vals = append(vals, val)
	}
}

func (p *parser) parseRecoveryExpr(recover *recoveryExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseRecoveryExpr (" + strings.Join(recover.failureLabel, ",") + ")"))
	}

	p.pushRecovery(recover.failureLabel, recover.recoverExpr)
	val, ok := p.parseExpr(recover.expr)
	p.popRecovery()

	return val, ok
}

func (p *parser) parseRuleRefExpr(ref *ruleRefExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseRuleRefExpr " + ref.name))
	}

	if ref.name == "" {
		panic(fmt.Sprintf("%s: invalid rule: missing name", ref.pos))
	}

	rule := p.rules[ref.name]
	if rule == nil {
		p.addErr(fmt.Errorf("undefined rule: %s", ref.name))
		return nil, false
	}
	return p.parseRule(rule)
}

func (p *parser) parseSeqExpr(seq *seqExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseSeqExpr"))
	}

	vals := make([]any, 0, len(seq.exprs))

	pt := p.pt
	state := p.cloneState()
	for _, expr := range seq.exprs {
		val, ok := p.parseExpr(expr)
		if !ok {
			p.restoreState(state)
			p.restore(pt)
			return nil, false
		}
		vals = append(vals, val)
	}
	return vals, true
}

func (p *parser) parseStateCodeExpr(state *stateCodeExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseStateCodeExpr"))
	}

	err := state.run(p)
	if err != nil {
		p.addErr(err)
	}
	return nil, true
}

func (p *parser) parseThrowExpr(expr *throwExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseThrowExpr"))
	}

	for i := len(p.recoveryStack) - 1; i >= 0; i-- {
		if recoverExpr, ok := p.recoveryStack[i][expr.label]; ok {
			if val, ok := p.parseExpr(recoverExpr); ok {
				return val, ok
			}
		}
	}

	return nil, false
}

func (p *parser) parseZeroOrMoreExpr(expr *zeroOrMoreExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseZeroOrMoreExpr"))
	}

	var vals []any

	for {
		p.pushV()
		val, ok := p.parseExpr(expr.expr)
		p.popV()
		if !ok {
			return vals, true
		}
		vals = append(vals, val)
	}
}

func (p *parser) parseZeroOrOneExpr(expr *zeroOrOneExpr) (any, bool) {
	if p.debug {
		defer p.out(p.in("parseZeroOrOneExpr"))
	}

	p.pushV()
	val, _ := p.parseExpr(expr.expr)
	p.popV()
	// whether it matched or not, consider it a match
	return val, true
}

[breml]

@cch123 Yes, it is known, that the master branch has this limitation. Do you mind to checkout the code from PR #123?