// ParserBox — Stage‑1 JSON v0 generator（extracted, simplified for Rust parser）
box ParserBox {
  gpos
  usings_json
  stage3

  birth() { me.gpos = 0 me.usings_json = "[]" me.stage3 = 0 return 0 }

  stage3_enable(flag) {
    if flag == null { flag = 0 }
    if flag == 0 { me.stage3 = 0 } else { me.stage3 = 1 }
    return 0
  }

  stage3_enabled() {
    if me.stage3 == 1 { return 1 }
    return 0
  }

  esc_json(s) {
    local out = ""
    local i = 0
    local n = s.length()
    loop(i < n) {
      local ch = s.substring(i, i+1)
      if ch == "\\" { out = out + "\\\\" } else { if ch == "\"" { out = out + "\\\"" } else { out = out + ch } }
      i = i + 1
    }
    return out
  }

  is_digit(ch) { return ch >= "0" && ch <= "9" }
  is_space(ch) { return ch == " " || ch == "\t" || ch == "\n" || ch == "\r" }
  // simple alpha/underscore check for identifiers
  is_alpha(ch) { return (ch >= "A" && ch <= "Z") || (ch >= "a" && ch <= "z") || ch == "_" }

  gpos_set(i) { me.gpos = i return 0 }
  gpos_get() { return me.gpos }

  // lightweight string helpers
  starts_with(src, i, pat) {
    local n = src.length()
    local m = pat.length()
    if i + m > n { return 0 }
    local k = 0
    loop(k < m) {
      if src.substring(i + k, i + k + 1) != pat.substring(k, k + 1) { return 0 }
      k = k + 1
    }
    return 1
  }
  index_of(src, i, pat) {
    local n = src.length()
    local m = pat.length()
    if m == 0 { return i }
    local j = i
    loop(j + m <= n) {
      if me.starts_with(src, j, pat) { return j }
      j = j + 1
    }
    return -1
  }
  trim(s) {
    local i = 0
    local n = s.length()
    loop(i < n && (s.substring(i,i+1) == " " || s.substring(i,i+1) == "\t")) { i = i + 1 }
    local j = n
    loop(j > i && (s.substring(j-1,j) == " " || s.substring(j-1,j) == "\t" || s.substring(j-1,j) == ";")) { j = j - 1 }
    return s.substring(i, j)
  }

  // keyword match at position i with word-boundary (next char not [A-Za-z0-9_])
  starts_with_kw(src, i, kw) {
    if me.starts_with(src, i, kw) == 0 { return 0 }
    local n = src.length()
    local j = i + kw.length()
    if j >= n { return 1 }
    local ch = src.substring(j, j+1)
    if me.is_alpha(ch) || me.is_digit(ch) { return 0 }
    return 1
  }

  // integer to string (uses string concat coercion)
  i2s(v) { return "" + v }

  // Read identifier starting at i: [A-Za-z_][A-Za-z0-9_]*; returns "name@pos"
  read_ident2(src, i) {
    local n = src.length()
    local j = i
    if j >= n { return "@" + me.i2s(i) }
    local ch = src.substring(j, j+1)
    if me.is_alpha(ch) == 0 { return "@" + me.i2s(i) }
    j = j + 1
    loop(j < n) {
      local c = src.substring(j, j+1)
      if me.is_alpha(c) || me.is_digit(c) { j = j + 1 } else { break }
    }
    local name = src.substring(i, j)
    return name + "@" + me.i2s(j)
  }

  // Read string literal at i (i points to '"'); returns raw content (no quotes), updates gpos
  read_string_lit(src, i) {
    local n = src.length()
    local j = i
    if j >= n || src.substring(j, j+1) != "\"" { me.gpos_set(i) return "" }
    j = j + 1
    local out = ""
    local guard = 0
    local max = 200000
    loop(j < n) {
      if guard > max { break } else { guard = guard + 1 }
      local ch = src.substring(j, j+1)
      if ch == "\"" { j = j + 1 me.gpos_set(j) return out }
      if ch == "\\" && j + 1 < n {
        local nx = src.substring(j+1, j+2)
        if nx == "\"" { out = out + "\"" } else { if nx == "\\" { out = out + "\\" } else { out = out + nx } }
        j = j + 2
      } else { out = out + ch j = j + 1 }
    }
    me.gpos_set(j)
    return out
  }

  // Append a using entry into usings_json (no-op acceptance path)
  add_using(kind, target, alias) {
    // kind: "path" or "ns"; target: path or namespace; alias: nullable
    local cur = me.usings_json
    if cur == null || cur.length() == 0 { cur = "[]" }
    // Build entry
    local name = ""
    local path = null
    if kind == "path" {
      path = target
      if alias != null { name = alias } else {
        local p = target
        // basename
        local idx = -1
        local t = 0
        loop(t < p.length()) { if p.substring(t,t+1) == "/" { idx = t } t = t + 1 }
        if idx >= 0 { p = p.substring(idx+1, p.length()) }
        if p.length() > 6 && me.starts_with(p, p.length()-6, ".nyash") == 1 { p = p.substring(0, p.length()-6) }
        name = p
      }
    } else {
      name = target
      if alias != null { name = alias }
    }
    local entry = "{\"name\":\"" + me.esc_json(name) + "\""
    if path != null { entry = entry + ",\"path\":\"" + me.esc_json(path) + "\"" }
    entry = entry + "}"
    // Insert before closing ']' of array
    if cur == "[]" { me.usings_json = "[" + entry + "]" return 0 }
    // naive append
    local pos = cur.lastIndexOf("]")
    if pos < 0 { me.usings_json = "[" + entry + "]" return 0 }
    me.usings_json = cur.substring(0, pos) + "," + entry + "]"
    return 0
  }

  // Collect `using` lines into JSON array stored in me.usings_json (no-op acceptance)
  extract_usings(src) {
    if src == null { me.usings_json = "[]" return 0 }
    local n = src.length()
    local i = 0
    local first = 1
    local out = "["
    loop(i < n) {
      // read a line
      local j = i
      loop(j < n && src.substring(j, j+1) != "\n") { j = j + 1 }
      local line = src.substring(i, j)
      // process
      local k = 0
      loop(k < line.length() && (line.substring(k,k+1) == " " || line.substring(k,k+1) == "\t")) { k = k + 1 }
      if me.starts_with(line, k, "using ") == 1 {
        local rest = me.trim(line.substring(k + 6, line.length()))
        // split on ' as '
        local as_pos = me.index_of(rest, 0, " as ")
        local target = rest
        local alias = null
        if as_pos >= 0 {
          target = me.trim(rest.substring(0, as_pos))
          alias = me.trim(rest.substring(as_pos + 4, rest.length()))
        }
        // path or namespace
        local is_path = 0
        if target.length() > 0 {
          if me.starts_with(target, 0, "\"") == 1 { is_path = 1 }
          if me.starts_with(target, 0, "./") == 1 { is_path = 1 }
          if me.starts_with(target, 0, "/") == 1 { is_path = 1 }
          if target.length() >= 6 && me.starts_with(target, target.length()-6, ".nyash") == 1 { is_path = 1 }
        }
        local name = ""
        local path = null
        if is_path == 1 {
          // trim quotes
          if me.starts_with(target, 0, "\"") == 1 {
            target = target.substring(1, target.length())
            if target.length() > 0 && target.substring(target.length()-1, target.length()) == "\"" {
              target = target.substring(0, target.length()-1)
            }
          }
          path = target
          if alias != null { name = alias } else {
            // derive from basename
            local p = target
            // find last '/'
            local idx = -1
            local t = 0
            loop(t < p.length()) { if p.substring(t,t+1) == "/" { idx = t } t = t + 1 }
            if idx >= 0 { p = p.substring(idx+1, p.length()) }
            // strip .nyash
            if p.length() > 6 && me.starts_with(p, p.length()-6, ".nyash") == 1 { p = p.substring(0, p.length()-6) }
            name = p
          }
        } else {
          name = target
        }
        // append JSON entry
        if first == 0 { out = out + "," } else { first = 0 }
        out = out + "{\"name\":\"" + me.esc_json(name) + "\""
        if path != null { out = out + ",\"path\":\"" + me.esc_json(path) + "\"" }
        out = out + "}"
      }
      i = j + 1
    }
    out = out + "]"
    me.usings_json = out
    return 0
  }
  get_usings_json() { return me.usings_json }

  to_int(s) { local n = s.length() if n == 0 { return 0 } local i = 0 local acc = 0 loop(i < n) { local d = s.substring(i, i+1) local dv = 0 if d == "1" { dv = 1 } else { if d == "2" { dv = 2 } else { if d == "3" { dv = 3 } else { if d == "4" { dv = 4 } else { if d == "5" { dv = 5 } else { if d == "6" { dv = 6 } else { if d == "7" { dv = 7 } else { if d == "8" { dv = 8 } else { if d == "9" { dv = 9 } } } } } } } } } acc = acc * 10 + dv i = i + 1 } return acc }

  skip_ws(src, i) { if src == null { return i } local n = src.length() local cont = 1 local guard = 0 local max = 100000 loop(cont == 1) { if guard > max { return i } guard = guard + 1 if i < n { if me.is_space(src.substring(i, i+1)) { i = i + 1 } else { cont = 0 } } else { cont = 0 } } return i }
  // identifiers/strings not required for Stage‑1 beyond string literal parse above

  // using metadata omitted in Stage‑1

  parse_number2(src, i) { local n = src.length() local j = i local cont = 1 local guard = 0 local max = 100000 loop(cont == 1) { if guard > max { cont = 0 } else { guard = guard + 1 if j < n { if me.is_digit(src.substring(j, j+1)) { j = j + 1 } else { cont = 0 } } else { cont = 0 } } } local s = src.substring(i, j) me.gpos_set(j) return "{\"type\":\"Int\",\"value\":" + s + "}" }
  parse_string2(src, i) { local n = src.length() local j = i + 1 local out = "" local guard = 0 local max = 200000 loop(j < n) { if guard > max { break } guard = guard + 1 local ch = src.substring(j, j+1) if ch == "\"" { j = j + 1 me.gpos_set(j) return "{\"type\":\"Str\",\"value\":\"" + me.esc_json(out) + "\"}" } if ch == "\\" && j + 1 < n { local nx = src.substring(j+1, j+2) if nx == "\"" { out = out + "\"" } else { if nx == "\\" { out = out + "\\" } else { out = out + nx } } j = j + 2 } else { out = out + ch j = j + 1 } } me.gpos_set(j) return "{\"type\":\"Str\",\"value\":\"" + me.esc_json(out) + "\"}" }

  parse_factor2(src, i) {
    local j = me.skip_ws(src, i)
    if j >= src.length() { me.gpos_set(j) return "{\"type\":\"Int\",\"value\":0}" }
    if me.starts_with_kw(src, j, "true") == 1 { me.gpos_set(j + 4) return "{\"type\":\"Bool\",\"value\":true}" }
    if me.starts_with_kw(src, j, "false") == 1 { me.gpos_set(j + 5) return "{\"type\":\"Bool\",\"value\":false}" }
    if me.starts_with_kw(src, j, "null") == 1 { me.gpos_set(j + 4) return "{\"type\":\"Null\"}" }
    local ch = src.substring(j, j+1)
    // Parenthesized
    if ch == "(" {
      local inner = me.parse_expr2(src, j + 1)
      local k = me.gpos_get()
      k = me.skip_ws(src, k)
      if src.substring(k, k+1) == ")" { k = k + 1 }
      me.gpos_set(k)
      return inner
    }
    // String literal
    if ch == "\"" { return me.parse_string2(src, j) }
    // Map literal: {"k": v, ...} (string keys only) → Call{name:"map.of", args:[Str(k1), v1, Str(k2), v2, ...]}
    if ch == "{" {
      local n = src.length()
      j = j + 1
      local out = "["
      local first = 1
      local cont = 1
      local guard = 0
      local max = 400000
      loop(cont == 1) {
        if guard > max { cont = 0 } else { guard = guard + 1 }
        j = me.skip_ws(src, j)
        if j >= n { cont = 0 } else {
          if src.substring(j, j+1) == "}" { j = j + 1 cont = 0 } else {
            // key (string only for Stage-2)
            if src.substring(j, j+1) != "\"" {
              // degrade by skipping one char to avoid infinite loop
              j = j + 1
              continue
            }
            local key_raw = me.read_string_lit(src, j)
            j = me.gpos_get()
            j = me.skip_ws(src, j)
            if src.substring(j, j+1) == ":" { j = j + 1 }
            j = me.skip_ws(src, j)
            local val_json = me.parse_expr2(src, j)
            j = me.gpos_get()
            local key_json = "{\"type\":\"Str\",\"value\":\"" + me.esc_json(key_raw) + "\"}"
            if first == 1 { out = out + key_json + "," + val_json first = 0 } else { out = out + "," + key_json + "," + val_json }
            // optional comma
            local before2 = j
            j = me.skip_ws(src, j)
            if j < n && src.substring(j, j+1) == "," { j = j + 1 }
            // progress guard (in case of malformed input)
            if j <= before2 { if j < n { j = j + 1 } else { j = n } }
          }
        }
      }
      out = out + "]"
      me.gpos_set(j)
      return "{\"type\":\"Call\",\"name\":\"map.of\",\"args\":" + out + "}"
    }
    // Array literal: [e1, e2, ...] → Call{name:"array.of", args:[...]}
    if ch == "[" {
      local n = src.length()
      j = j + 1
      local out = "["
      local first = 1
      local cont = 1
      local guard = 0
      local max = 400000
      loop(cont == 1) {
        if guard > max { cont = 0 } else { guard = guard + 1 }
        j = me.skip_ws(src, j)
        if j >= n { cont = 0 } else {
          if src.substring(j, j+1) == "]" { j = j + 1 cont = 0 } else {
            local before = j
            local ej = me.parse_expr2(src, j)
            j = me.gpos_get()
            if first == 1 { out = out + ej first = 0 } else { out = out + "," + ej }
            // optional comma+whitespace
            local before2 = j
            j = me.skip_ws(src, j)
            if j < n && src.substring(j, j+1) == "," { j = j + 1 }
            // progress guard
            if j <= before { if j < n { j = j + 1 } else { j = n } }
          }
        }
      }
      out = out + "]"
      me.gpos_set(j)
      return "{\"type\":\"Call\",\"name\":\"array.of\",\"args\":" + out + "}"
    }
    // true/false
    if me.starts_with_kw(src, j, "true") == 1 { me.gpos_set(j + 4) return "{\"type\":\"Bool\",\"value\":true}" }
    if me.starts_with_kw(src, j, "false") == 1 { me.gpos_set(j + 5) return "{\"type\":\"Bool\",\"value\":false}" }
    // new Class(args)
    if me.starts_with_kw(src, j, "new") == 1 {
      local p = me.skip_ws(src, j + 3)
      local idp = me.read_ident2(src, p)
      local at = idp.lastIndexOf("@")
      local cls = idp.substring(0, at)
      local k = me.to_int(idp.substring(at+1, idp.length()))
      k = me.skip_ws(src, k)
      if src.substring(k, k+1) == "(" { k = k + 1 }
      local args_and_pos = me.parse_args2(src, k)
      local at2 = args_and_pos.lastIndexOf("@")
      local args_json = args_and_pos.substring(0, at2)
      k = me.to_int(args_and_pos.substring(at2+1, args_and_pos.length()))
      k = me.skip_ws(src, k)
      if src.substring(k, k+1) == ")" { k = k + 1 }
      me.gpos_set(k)
      return "{\"type\":\"New\",\"class\":\"" + cls + "\",\"args\":" + args_json + "}"
    }
    // Identifier / Call / Method chain
    if me.is_alpha(ch) {
      local idp = me.read_ident2(src, j)
      local at = idp.lastIndexOf("@")
      local name = idp.substring(0, at)
      local k = me.to_int(idp.substring(at+1, idp.length()))
      local node = "{\"type\":\"Var\",\"name\":\"" + name + "\"}"
      local cont2 = 1
      loop(cont2 == 1) {
        k = me.skip_ws(src, k)
        local tch = src.substring(k, k+1)
        if tch == "(" {
          k = k + 1
          local args_and_pos = me.parse_args2(src, k)
          local at2 = args_and_pos.lastIndexOf("@")
          local args_json = args_and_pos.substring(0, at2)
          k = me.to_int(args_and_pos.substring(at2+1, args_and_pos.length()))
          k = me.skip_ws(src, k)
          if src.substring(k, k+1) == ")" { k = k + 1 }
          node = "{\"type\":\"Call\",\"name\":\"" + name + "\",\"args\":" + args_json + "}"
        } else {
          if tch == "." {
            k = k + 1
            k = me.skip_ws(src, k)
            local midp = me.read_ident2(src, k)
            local at3 = midp.lastIndexOf("@")
            local mname = midp.substring(0, at3)
            k = me.to_int(midp.substring(at3+1, midp.length()))
            k = me.skip_ws(src, k)
            if src.substring(k, k+1) == "(" { k = k + 1 }
            local args2 = me.parse_args2(src, k)
            local at4 = args2.lastIndexOf("@")
            local args_json2 = args2.substring(0, at4)
            k = me.to_int(args2.substring(at4+1, args2.length()))
            k = me.skip_ws(src, k)
            if src.substring(k, k+1) == ")" { k = k + 1 }
            node = "{\"type\":\"Method\",\"recv\":" + node + ",\"method\":\"" + mname + "\",\"args\":" + args_json2 + "}"
          } else { cont2 = 0 }
        }
      }
      me.gpos_set(k)
      return node
    }
    // Fallback: number
    return me.parse_number2(src, j)
  }
  // unary minus binds tighter than * /
  parse_unary2(src, i) {
    local j = me.skip_ws(src, i)
    if src.substring(j, j+1) == "-" {
      local rhs = me.parse_factor2(src, j + 1)
      j = me.gpos_get()
      local zero = "{\"type\":\"Int\",\"value\":0}"
      me.gpos_set(j)
      return "{\"type\":\"Binary\",\"op\":\"-\",\"lhs\":" + zero + ",\"rhs\":" + rhs + "}"
    }
    return me.parse_factor2(src, j)
  }
  parse_term2(src, i) { local lhs = me.parse_unary2(src, i) local j = me.gpos_get() local cont = 1 loop(cont == 1) { j = me.skip_ws(src, j) if j >= src.length() { cont = 0 } else { local op = src.substring(j, j+1) if op != "*" && op != "/" { cont = 0 } else { local rhs = me.parse_unary2(src, j+1) j = me.gpos_get() lhs = "{\"type\":\"Binary\",\"op\":\"" + op + "\",\"lhs\":" + lhs + ",\"rhs\":" + rhs + "}" } } } me.gpos_set(j) return lhs }
  parse_sum2(src, i) { local lhs = me.parse_term2(src, i) local j = me.gpos_get() local cont = 1 loop(cont == 1) { j = me.skip_ws(src, j) if j >= src.length() { cont = 0 } else { local op = src.substring(j, j+1) if op != "+" && op != "-" { cont = 0 } else { local rhs = me.parse_term2(src, j+1) j = me.gpos_get() lhs = "{\"type\":\"Binary\",\"op\":\"" + op + "\",\"lhs\":" + lhs + ",\"rhs\":" + rhs + "}" } } } me.gpos_set(j) return lhs }
  parse_compare2(src, i) { local lhs = me.parse_sum2(src, i) local j = me.gpos_get() j = me.skip_ws(src, j) local two = src.substring(j, j+2) local one = src.substring(j, j+1) local op = "" if two == "==" || two == "!=" || two == "<=" || two == ">=" { op = two j = j + 2 } else { if one == "<" || one == ">" { op = one j = j + 1 } } if op == "" { me.gpos_set(j) return lhs } local rhs = me.parse_sum2(src, j) j = me.gpos_get() me.gpos_set(j) return "{\"type\":\"Compare\",\"op\":\"" + op + "\",\"lhs\":" + lhs + ",\"rhs\":" + rhs + "}" }
  parse_expr2(src, i) {
    local lhs = me.parse_compare2(src, i)
    local j = me.gpos_get()
    local cont = 1
    loop(cont == 1) {
      j = me.skip_ws(src, j)
      local two = src.substring(j, j+2)
      if two != "&&" && two != "||" { cont = 0 } else {
        local rhs = me.parse_compare2(src, j+2)
        j = me.gpos_get()
        lhs = "{\"type\":\"Logical\",\"op\":\"" + two + "\",\"lhs\":" + lhs + ",\"rhs\":" + rhs + "}"
      }
    }
    j = me.skip_ws(src, j)
    if src.substring(j, j+1) == "?" {
      j = j + 1
      j = me.skip_ws(src, j)
      local then_expr = me.parse_expr2(src, j)
      j = me.gpos_get()
      j = me.skip_ws(src, j)
      if src.substring(j, j+1) == ":" { j = j + 1 }
      j = me.skip_ws(src, j)
      local else_expr = me.parse_expr2(src, j)
      j = me.gpos_get()
      if else_expr.length() == 0 { else_expr = "{\"type\":\"Int\",\"value\":0}" }
      me.gpos_set(j)
      return "{\"type\":\"Ternary\",\"cond\":" + lhs + ",\"then\":" + then_expr + ",\"else\":" + else_expr + "}"
    }
    me.gpos_set(j)
    return lhs
  }
  parse_args2(src, i) {
    local j = me.skip_ws(src, i)
    local n = src.length()
    local out = "["
    j = me.skip_ws(src, j)
    if j < n && src.substring(j, j+1) == ")" { return "[]@" + me.i2s(j) }
    // first argument
    local e = me.parse_expr2(src, j)
    j = me.gpos_get()
    out = out + e
    // subsequent arguments with guard
    local cont_args = 1
    local guard = 0
    local max = 100000
    loop(cont_args == 1) {
      if guard > max { cont_args = 0 } else { guard = guard + 1 }
      local before = j
      j = me.skip_ws(src, j)
      if j < n && src.substring(j, j+1) == "," {
        j = j + 1
        j = me.skip_ws(src, j)
        e = me.parse_expr2(src, j)
        j = me.gpos_get()
        out = out + "," + e
      } else { cont_args = 0 }
      if j == before { cont_args = 0 }
    }
    out = out + "]"
    return out + "@" + me.i2s(j)
  }
  parse_stmt2(src, i) {
    local j = me.skip_ws(src, i)
    local stmt_start = j
    if me.starts_with_kw(src, j, "using") == 1 {
      j = j + 5
      j = me.skip_ws(src, j)
      if src.substring(j, j+1) == "\"" {
        local p = me.read_string_lit(src, j)
        j = me.gpos_get()
        j = me.skip_ws(src, j)
        local alias = null
        if me.starts_with_kw(src, j, "as") == 1 { j = j + 2 j = me.skip_ws(src, j) local idp = me.read_ident2(src, j) local at = idp.lastIndexOf("@") alias = idp.substring(0, at) j = me.to_int(idp.substring(at+1, idp.length())) }
        me.add_using("path", p, alias)
      } else {
        if me.is_alpha(src.substring(j, j+1)) {
          local idp = me.read_ident2(src, j)
          local at = idp.lastIndexOf("@")
          local name = idp.substring(0, at)
          j = me.to_int(idp.substring(at+1, idp.length()))
          local cont = 1
          loop(cont == 1) {
            j = me.skip_ws(src, j)
            if src.substring(j, j+1) == "." { j = j + 1 j = me.skip_ws(src, j) idp = me.read_ident2(src, j) at = idp.lastIndexOf("@") name = name + "." + idp.substring(0, at) j = me.to_int(idp.substring(at+1, idp.length())) } else { cont = 0 }
          }
          j = me.skip_ws(src, j)
          local alias2 = null
          if me.starts_with_kw(src, j, "as") == 1 { j = j + 2 j = me.skip_ws(src, j) idp = me.read_ident2(src, j) at = idp.lastIndexOf("@") alias2 = idp.substring(0, at) j = me.to_int(idp.substring(at+1, idp.length())) }
          me.add_using("ns", name, alias2)
        }
      }
      // ensure progress
      if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
      me.gpos_set(j)
      return ""
    }
    // simple assignment: IDENT '=' expr ;  → JSON v0 Local{name, expr} (Stage‑2 uses Local for updates)
    if j < src.length() && me.is_alpha(src.substring(j, j+1)) {
      local idp0 = me.read_ident2(src, j)
      local at0 = idp0.lastIndexOf("@")
      if at0 > 0 {
        local name0 = idp0.substring(0, at0)
        local k0 = me.to_int(idp0.substring(at0+1, idp0.length()))
        k0 = me.skip_ws(src, k0)
        if k0 < src.length() && src.substring(k0, k0+1) == "=" {
          local eq_two = "="
          if k0 + 1 < src.length() { eq_two = src.substring(k0, k0+2) }
          if eq_two != "==" {
            k0 = k0 + 1
            k0 = me.skip_ws(src, k0)
            local default_local = "{\"type\":\"Int\",\"value\":0}"
            local expr_json0 = default_local
            local end_pos0 = k0
            if k0 < src.length() {
              local ahead = src.substring(k0, k0+1)
              if ahead != "}" && ahead != ";" {
                expr_json0 = me.parse_expr2(src, k0)
                end_pos0 = me.gpos_get()
              }
            }
            k0 = end_pos0
            if k0 <= stmt_start { if k0 < src.length() { k0 = k0 + 1 } else { k0 = src.length() } }
            me.gpos_set(k0)
            return "{\"type\":\"Local\",\"name\":\"" + name0 + "\",\"expr\":" + expr_json0 + "}"
          }
        }
      }
    }
    if me.starts_with_kw(src, j, "return") == 1 {
      j = j + 6
      j = me.skip_ws(src, j)
      local default_ret = "{\"type\":\"Int\",\"value\":0}"
      local expr_json_ret = default_ret
      local end_pos_ret = j
      if j < src.length() {
        local ahead_ret = src.substring(j, j+1)
        if ahead_ret != "}" && ahead_ret != ";" {
          expr_json_ret = me.parse_expr2(src, j)
          end_pos_ret = me.gpos_get()
        }
      }
      j = end_pos_ret
      if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
      me.gpos_set(j)
      return "{\"type\":\"Return\",\"expr\":" + expr_json_ret + "}"
    }
    if me.starts_with_kw(src, j, "local") == 1 {
      j = j + 5
      j = me.skip_ws(src, j)
      local idp = me.read_ident2(src, j)
      local at = idp.lastIndexOf("@")
      local name = idp.substring(0, at)
      j = me.to_int(idp.substring(at+1, idp.length()))
      j = me.skip_ws(src, j)
      if j < src.length() && src.substring(j, j+1) == "=" { j = j + 1 }
      j = me.skip_ws(src, j)
      local default_local = "{\"type\":\"Int\",\"value\":0}"
      local expr_json_local = default_local
      local end_pos_local = j
      if j < src.length() {
        local ahead_local = src.substring(j, j+1)
        if ahead_local != "}" && ahead_local != ";" {
          expr_json_local = me.parse_expr2(src, j)
          end_pos_local = me.gpos_get()
        }
      }
      j = end_pos_local
      if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
      me.gpos_set(j)
      return "{\"type\":\"Local\",\"name\":\"" + name + "\",\"expr\":" + expr_json_local + "}"
    }
    if me.starts_with_kw(src, j, "if") == 1 {
      j = j + 2
      j = me.skip_ws(src, j)
      local paren = 0
      if src.substring(j, j+1) == "(" { paren = 1 j = j + 1 }
      local cond = me.parse_expr2(src, j)
      j = me.gpos_get()
      if paren == 1 { j = me.skip_ws(src, j) if src.substring(j, j+1) == ")" { j = j + 1 } }
      j = me.skip_ws(src, j)
      local then_res = me.parse_block2(src, j)
      local at1 = then_res.lastIndexOf("@")
      local then_json = then_res.substring(0, at1)
      j = me.to_int(then_res.substring(at1+1, then_res.length()))
      j = me.skip_ws(src, j)
      local else_json = null
      if me.starts_with_kw(src, j, "else") == 1 { j = j + 4 j = me.skip_ws(src, j) local else_res = me.parse_block2(src, j) local at2 = else_res.lastIndexOf("@") else_json = else_res.substring(0, at2) j = me.to_int(else_res.substring(at2+1, else_res.length())) }
      if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
      me.gpos_set(j)
      if else_json == null { return "{\"type\":\"If\",\"cond\":" + cond + ",\"then\":" + then_json + "}" } else { return "{\"type\":\"If\",\"cond\":" + cond + ",\"then\":" + then_json + ",\"else\":" + else_json + "}" }
    }
    if me.starts_with_kw(src, j, "loop") == 1 {
      j = j + 4
      j = me.skip_ws(src, j)
      if src.substring(j, j+1) == "(" { j = j + 1 }
      local cond = me.parse_expr2(src, j)
      j = me.gpos_get()
      j = me.skip_ws(src, j)
      if src.substring(j, j+1) == ")" { j = j + 1 }
      j = me.skip_ws(src, j)
      local body_res = me.parse_block2(src, j)
      local at3 = body_res.lastIndexOf("@")
      local body_json = body_res.substring(0, at3)
      j = me.to_int(body_res.substring(at3+1, body_res.length()))
      if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
      me.gpos_set(j)
      return "{\"type\":\"Loop\",\"cond\":" + cond + ",\"body\":" + body_json + "}"
    }
    // Stage-3 acceptance (syntax only): break / continue → no-op expression
    if me.starts_with_kw(src, j, "break") == 1 {
      j = j + 5
      if me.stage3_enabled() == 1 {
        j = me.skip_ws(src, j)
        if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
        me.gpos_set(j)
        return "{\"type\":\"Break\"}"
      }
      if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
      me.gpos_set(j)
      return "{\"type\":\"Expr\",\"expr\":{\"type\":\"Int\",\"value\":0}}"
    }
    if me.starts_with_kw(src, j, "continue") == 1 {
      j = j + 8
      if me.stage3_enabled() == 1 {
        j = me.skip_ws(src, j)
        if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
        me.gpos_set(j)
        return "{\"type\":\"Continue\"}"
      }
      if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
      me.gpos_set(j)
      return "{\"type\":\"Expr\",\"expr\":{\"type\":\"Int\",\"value\":0}}"
    }
    // Stage-3 acceptance: throw expr → degrade to Expr(expr)
    if me.starts_with_kw(src, j, "throw") == 1 {
      j = j + 5
      j = me.skip_ws(src, j)
      local e_throw = me.parse_expr2(src, j)
      j = me.gpos_get()
      if me.stage3_enabled() == 1 {
        if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
        me.gpos_set(j)
        return "{\"type\":\"Throw\",\"expr\":" + e_throw + "}"
      }
      if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
      me.gpos_set(j)
      return "{\"type\":\"Expr\",\"expr\":" + e_throw + "}"
    }
    // Stage-3 acceptance: try { ... } (catch ...)* (finally { ... })? → degrade to no-op (syntax only)
    if me.starts_with_kw(src, j, "try") == 1 {
      j = j + 3
      j = me.skip_ws(src, j)
      // parse try block
      local try_res = me.parse_block2(src, j)
      local at_t = try_res.lastIndexOf("@")
      local try_json = try_res.substring(0, at_t)
      j = me.to_int(try_res.substring(at_t+1, try_res.length()))
      local catches_json = "["
      local catch_first = 1
      // zero or more catch
      local guard_ct = 0
      local max_ct = 100
      local cont_ct = 1
      loop(cont_ct == 1) {
        if guard_ct > max_ct { cont_ct = 0 } else { guard_ct = guard_ct + 1 }
        j = me.skip_ws(src, j)
        if me.starts_with_kw(src, j, "catch") == 1 {
          j = j + 5
          j = me.skip_ws(src, j)
          local catch_type = null
          local catch_param = null
          if src.substring(j, j+1) == "(" { j = j + 1 j = me.skip_ws(src, j)
            // optional type + name
            if me.is_alpha(src.substring(j, j+1)) {
              local id1 = me.read_ident2(src, j)
              local at1 = id1.lastIndexOf("@")
              catch_type = id1.substring(0, at1)
              j = me.to_int(id1.substring(at1+1, id1.length()))
              j = me.skip_ws(src, j)
            }
            if me.is_alpha(src.substring(j, j+1)) {
              local id2 = me.read_ident2(src, j)
              local at2 = id2.lastIndexOf("@")
              catch_param = id2.substring(0, at2)
              j = me.to_int(id2.substring(at2+1, id2.length()))
              j = me.skip_ws(src, j)
            }
            if src.substring(j, j+1) == ")" { j = j + 1 }
          }
          j = me.skip_ws(src, j)
          // catch body
          local c_res = me.parse_block2(src, j)
          local atc = c_res.lastIndexOf("@")
          j = me.to_int(c_res.substring(atc+1, c_res.length()))
          if me.stage3_enabled() == 1 {
            local entry = "{"
            local wrote = 0
            if catch_param != null && catch_param.length() > 0 { entry = entry + "\"param\":\"" + me.esc_json(catch_param) + "\"" wrote = 1 }
            if catch_type != null && catch_type.length() > 0 { if wrote == 1 { entry = entry + "," } entry = entry + "\"typeHint\":\"" + me.esc_json(catch_type) + "\"" wrote = 1 }
            local body_json = c_res.substring(0, atc)
            if wrote == 1 { entry = entry + "," }
            entry = entry + "\"body\":" + body_json + "}"
            if catch_first == 0 { catches_json = catches_json + "," + entry } else { catches_json = catches_json + entry catch_first = 0 }
          }
        } else { cont_ct = 0 }
      }
      catches_json = catches_json + "]"
      // optional finally
      j = me.skip_ws(src, j)
      local finally_json = null
      if me.starts_with_kw(src, j, "finally") == 1 {
        j = j + 7
        j = me.skip_ws(src, j)
        local f_res = me.parse_block2(src, j)
        local atf = f_res.lastIndexOf("@")
        j = me.to_int(f_res.substring(atf+1, f_res.length()))
        finally_json = f_res.substring(0, atf)
      }
      if me.stage3_enabled() == 1 {
        if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
        me.gpos_set(j)
        local node = "{\"type\":\"Try\",\"try\":" + try_json + ",\"catches\":" + catches_json
        if finally_json != null { node = node + ",\"finally\":" + finally_json }
        node = node + "}"
        return node
      }
      if j <= stmt_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
      me.gpos_set(j)
      return "{\"type\":\"Expr\",\"expr\":{\"type\":\"Int\",\"value\":0}}"
    }
    // Fallback: expression or unknown token — ensure progress even on malformed input
    local expr_start = j
    local e = me.parse_expr2(src, j)
    j = me.gpos_get()
    if j <= expr_start { if j < src.length() { j = j + 1 } else { j = src.length() } }
    me.gpos_set(j)
    return "{\"type\":\"Expr\",\"expr\":" + e + "}"
  }
  parse_block2(src, i) {
    local j = me.skip_ws(src, i)
    if src.substring(j, j+1) != "{" { return "[]@" + me.i2s(j) }
    j = j + 1
    local body = "["
    local first = 1
    local cont_block = 1
    loop(cont_block == 1) {
      j = me.skip_ws(src, j)
      if j >= src.length() { cont_block = 0 } else {
        if src.substring(j, j+1) == "}" { j = j + 1 cont_block = 0 } else {
          local start_j = j
          local s = me.parse_stmt2(src, j)
          j = me.gpos_get()
          // Progress guard: ensure forward movement to avoid infinite loop on malformed input
          if j <= start_j {
            if j < src.length() { j = j + 1 } else { j = src.length() }
            me.gpos_set(j)
          }
          // consume optional semicolons (ASI minimal)
          local done = 0
          local guard = 0
          local max = 100000
          loop(done == 0) {
            if guard > max { done = 1 } else { guard = guard + 1 }
            local before = j
            j = me.skip_ws(src, j)
            if j < src.length() && src.substring(j, j+1) == ";" { j = j + 1 } else { done = 1 }
            if j == before { done = 1 }
          }
          if s.length() > 0 { if first == 1 { body = body + s first = 0 } else { body = body + "," + s } }
        }
      }
    }
    body = body + "]"
    return body + "@" + me.i2s(j)
  }
  parse_program2(src) {
    local i = me.skip_ws(src, 0)
    local body = "["
    local first = 1
    local cont_prog = 1
    loop(cont_prog == 1) {
      i = me.skip_ws(src, i)
      if i >= src.length() { cont_prog = 0 } else {
        local start_i = i
        local s = me.parse_stmt2(src, i)
        i = me.gpos_get()
        // Progress guard: ensure forward movement to avoid infinite loop on malformed input
        if i <= start_i {
          if i < src.length() { i = i + 1 } else { i = src.length() }
          me.gpos_set(i)
        }
        // consume optional semicolons between top-level statements
        local done2 = 0
        local guard2 = 0
        local max2 = 100000
        loop(done2 == 0) {
          if guard2 > max2 { done2 = 1 } else { guard2 = guard2 + 1 }
          local before2 = i
          i = me.skip_ws(src, i)
          if i < src.length() && src.substring(i, i+1) == ";" { i = i + 1 } else { done2 = 1 }
          if i == before2 { done2 = 1 }
        }
        if s.length() > 0 { if first == 1 { body = body + s first = 0 } else { body = body + "," + s } }
      }
    }
    body = body + "]"
    return "{\"version\":0,\"kind\":\"Program\",\"body\":" + body + "}"
  }
}

static box ParserStub { main(args) { return 0 } }