parseLPAREN

    pub fn parseLPAREN(p: *Parser) Error!bool {
        const def_index = @backingInt(Def.defLPAREN);
        if (p.depths[def_index] > max_depth) return error.MaxDepth;
        p.depths[def_index] += 1;
        defer p.depths[def_index] -= 1;
        return blk_0: {
            const pos_0 = p.i;
            if (try p.parseskip() and blk_1: {
                if (std.mem.startsWith(u8, p.source[p.i..], "(")) {
                    p.i += 1;
                    break :blk_1 true;
                }
                break :blk_1 false;
            }) break :blk_0 true;
            p.i = pos_0;
            break :blk_0 false;
        };
    }