parsePLUS

    pub fn parsePLUS(p: *Parser) Error!bool {
        const def_index = @backingInt(Def.defPLUS);
        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;
            } and blk_1: {
                const pos_1 = p.i;
                const match_1 = (p.i < p.source.len and switch (p.source[p.i]) {
                    '%'...'%',
                    '+'...'+',
                    '='...'=',
                    '|'...'|',
                    => blk_2: {
                        p.i += 1;
                        break :blk_2 true;
                    },
                    else => false,
                });
                p.i = pos_1;
                break :blk_1 !match_1;
            }) break :blk_0 true;
            p.i = pos_0;
            break :blk_0 false;
        };
    }