hakorune/tools/hako_check/rules/rule_dead_code.hako

// tools/hako_check/rules/rule_dead_code.hako — HC019: Comprehensive Dead Code Detection
// Unified dead code analyzer combining method-level, block-level, and box-level detection.
// Phase 153: Revival of dead code detection mode with JoinIR integration.

static box DeadCodeAnalyzerBox {
  // Main entry point for comprehensive dead code analysis
  // Input: ir (Analysis IR), path (file path), out (diagnostics array)
  // Returns: void (like other rules)
  method apply_ir(ir, path, out) {
    // Phase 153 MVP: Focus on method-level reachability
    // Block-level analysis deferred to Phase 154+ when MIR JSON integration is ready

    if ir == null { return }
    if out == null { return }

    // 1. Analyze unreachable methods (similar to HC011 but enhanced)
    me._analyze_dead_methods(ir, path, out)

    // 2. Analyze dead static boxes (similar to HC012 but integrated)
    me._analyze_dead_boxes(ir, path, out)

    // 3. TODO(Phase 154): Analyze unreachable blocks (requires MIR CFG)
    // me._analyze_unreachable_blocks(ir, path, out)

    return
  }

  // Analyze unreachable methods using DFS from entrypoints
  _analyze_dead_methods(ir, path, out) {
    local methods = ir.get("methods")
    if methods == null || methods.size() == 0 {
      // Fallback: scan from source text
      local src = ir.get("source")
      if src != null {
        methods = me._scan_methods_from_text(src)
      } else {
        return
      }
    }

    if methods == null || methods.size() == 0 { return }

    local calls = ir.get("calls")
    if calls == null || calls.size() == 0 {
      // Build minimal calls from source text
      local src = ir.get("source")
      if src != null {
        calls = me._scan_calls_from_text(src)
      } else {
        calls = new ArrayBox()
      }
    }

    local eps = ir.get("entrypoints")
    if eps == null { eps = new ArrayBox() }

    // Build adjacency graph
    local adj = new MapBox()
    local i = 0
    while i < methods.size() {
      adj.set(methods.get(i), new ArrayBox())
      i = i + 1
    }

    // Add edges from calls
    i = 0
    while i < calls.size() {
      local c = calls.get(i)
      local f = c.get("from")
      local t = c.get("to")

      // Normalize from: prefer exact, otherwise try adding "/0" suffix
      local ff = f
      if adj.has(ff) == 0 {
        local f0 = f + "/0"
        if adj.has(f0) == 1 { ff = f0 }
      }

      if adj.has(ff) == 1 {
        adj.get(ff).push(t)
      }

      i = i + 1
    }

    // DFS from entrypoints
    local seen = new MapBox()
    local seeds = me._resolve_entrypoints(eps, adj, methods)

    local j = 0
    while j < seeds.size() {
      me._dfs(adj, seeds.get(j), seen)
      j = j + 1
    }

    // Report dead methods (not seen)
    local src_text = ir.get("source")
    i = 0
    while i < methods.size() {
      local m = methods.get(i)
      if seen.has(m) == 0 {
        // Check if method is actually called via text heuristic (reduce false positives)
        local keep = 1
        if src_text != null {
          local slash = m.lastIndexOf("/")
          local dotp = m.lastIndexOf(".")
          if dotp >= 0 {
            local meth = (slash > dotp) ? m.substring(dotp+1, slash) : m.substring(dotp+1)
            if src_text.indexOf("." + meth + "(") >= 0 {
              keep = 0
            }
          }
        }

        if keep == 1 {
          out.push("[HC019] unreachable method (dead code): " + path + " :: " + m)
        }
      }
      i = i + 1
    }

    return
  }

  // Analyze dead static boxes (never referenced)
  _analyze_dead_boxes(ir, path, out) {
    local boxes = ir.get("boxes")
    if boxes == null { return }

    local calls = ir.get("calls")
    if calls == null { return }

    // Collect all box names referenced in calls
    local referenced_boxes = new MapBox()
    local ci = 0
    while ci < calls.size() {
      local call = calls.get(ci)
      if call == null { ci = ci + 1; continue }

      local to = call.get("to")
      if to != null {
        // Extract box name from qualified call (e.g., "Box.method/0" -> "Box")
        local dot = to.indexOf(".")
        if dot > 0 {
          local box_name = to.substring(0, dot)
          referenced_boxes.set(box_name, "1")
        }
      }
      ci = ci + 1
    }

    // Check each box
    local findings = 0
    local bi = 0
    while bi < boxes.size() {
      local box_info = boxes.get(bi)
      if box_info == null { bi = bi + 1; continue }

      local name = box_info.get("name")
      if name == null { bi = bi + 1; continue }

      local is_static = box_info.get("is_static")

      // Skip Main box (entry point)
      if name == "Main" { bi = bi + 1; continue }

      // Only check static boxes
      if is_static != null {
        if is_static == 0 { bi = bi + 1; continue }
      }

      // Check if box is referenced
      local ref_check = referenced_boxes.get(name)

      if ref_check == null || ref_check != "1" {
        // Box is never referenced - report error
        local line_any = box_info.get("span_line")
        local line_s = ""
        if line_any == null {
          line_s = "1"
        } else {
          line_s = "" + line_any
        }

        // Parse leading digits
        local i = 0
        local digits = ""
        while i < line_s.length() {
          local ch = line_s.substring(i, i+1)
          if ch >= "0" && ch <= "9" {
            digits = digits + ch
            i = i + 1
            continue
          }
          break
        }
        if digits == "" { digits = "1" }

        out.push("[HC019] dead static box (never referenced): " + name + " :: " + path + ":" + digits)
      }

      bi = bi + 1
    }

    return
  }

  // Resolve entrypoints to actual method names in adjacency graph
  _resolve_entrypoints(eps, adj, methods) {
    local seeds = new ArrayBox()

    // Collect keys from methods array
    local keys = new ArrayBox()
    local i = 0
    while i < methods.size() {
      keys.push(methods.get(i))
      i = i + 1
    }

    // Try to match each entrypoint
    local j = 0
    while j < eps.size() {
      local ep = eps.get(j)

      // Exact match
      if adj.has(ep) == 1 {
        seeds.push(ep)
      }

      // Prefix match: ep + "/"
      local pref = ep + "/"
      local k = 0
      while k < keys.size() {
        local key = keys.get(k)
        if key.indexOf(pref) == 0 {
          seeds.push(key)
        }
        k = k + 1
      }

      j = j + 1
    }

    // Fallback: common Main.main/0 if still empty
    if seeds.size() == 0 {
      if adj.has("Main.main/0") == 1 {
        seeds.push("Main.main/0")
      }
    }

    return seeds
  }

  // DFS traversal for reachability
  _dfs(adj, node, seen) {
    if node == null { return }
    if seen.has(node) == 1 { return }

    seen.set(node, 1)

    if adj.has(node) == 0 { return }

    local arr = adj.get(node)
    local k = 0
    while k < arr.size() {
      me._dfs(adj, arr.get(k), seen)
      k = k + 1
    }
  }

  // Scan methods from source text (fallback when IR is incomplete)
  _scan_methods_from_text(text) {
    local res = new ArrayBox()
    if text == null { return res }

    local lines = me._split_lines(text)
    local cur = null
    local depth = 0
    local i = 0

    while i < lines.size() {
      local ln = me._ltrim(lines.get(i))

      if ln.indexOf("static box ") == 0 {
        local rest = ln.substring("static box ".length())
        local p = rest.indexOf("{")
        if p > 0 {
          cur = me._rstrip(rest.substring(0, p))
        } else {
          cur = me._rstrip(rest)
        }
        depth = depth + 1
        i = i + 1
        continue
      }

      if cur != null && ln.indexOf("method ") == 0 {
        local rest = ln.substring("method ".length())
        local p1 = rest.indexOf("(")
        local name = (p1 > 0) ? me._rstrip(rest.substring(0, p1)) : me._rstrip(rest)

        local ar = 0
        local p2 = rest.indexOf(")", (p1 >= 0) ? (p1+1) : 0)
        if p1 >= 0 && p2 > p1+1 {
          local inside = rest.substring(p1+1, p2)
          // Count commas + 1 if any non-space
          local any = 0
          local cnt = 1
          local k = 0
          while k < inside.length() {
            local c = inside.substring(k, k+1)
            if c == "," { cnt = cnt + 1 }
            if c != " " && c != "\t" { any = 1 }
            k = k + 1
          }
          if any == 1 { ar = cnt }
        }

        res.push(cur + "." + name + "/" + me._itoa(ar))
      }

      // Adjust depth by braces
      local j = 0
      while j < ln.length() {
        local ch = ln.substring(j, j+1)
        if ch == "{" {
          depth = depth + 1
        } else {
          if ch == "}" {
            depth = depth - 1
            if depth < 0 { depth = 0 }
          }
        }
        j = j + 1
      }

      if depth == 0 { cur = null }

      i = i + 1
    }

    return res
  }

  // Scan calls from source text (fallback)
  _scan_calls_from_text(text) {
    local arr = new ArrayBox()
    if text == null { return arr }

    local lines = me._split_lines(text)
    local src_m = "Main.main/0"
    local i = 0

    while i < lines.size() {
      local ln = lines.get(i)
      // Naive: detect patterns like "Main.foo("
      local pos = 0
      local n = ln.length()

      loop (pos < n) {
        local k = ln.indexOf(".", pos)
        if k < 0 { break }

        // Scan ident before '.'
        local lhs = me._scan_ident_rev(ln, k-1)
        // Scan ident after '.'
        local rhs = me._scan_ident_fwd(ln, k+1)

        if lhs != null && rhs != null {
          local to = lhs + "." + rhs + "/0"
          local rec = new MapBox()
          rec.set("from", src_m)
          rec.set("to", to)
          arr.push(rec)
        }

        pos = k + 1
      }

      i = i + 1
    }

    return arr
  }

  // Helper: scan identifier backwards from position
  _scan_ident_rev(s, i) {
    if i < 0 { return null }

    local n = i
    local start = 0
    local rr = 0

    while rr <= n {
      local j = i - rr
      local c = s.substring(j, j+1)

      if me._is_ident_char(c) == 0 {
        start = j+1
        break
      }

      if j == 0 {
        start = 0
        break
      }

      rr = rr + 1
    }

    if start > i { return null }
    return s.substring(start, i+1)
  }

  // Helper: scan identifier forwards from position
  _scan_ident_fwd(s, i) {
    local n = s.length()
    if i >= n { return null }

    local endp = i
    local off = 0

    while off < n {
      local j = i + off
      if j >= n { break }

      local c = s.substring(j, j+1)

      if me._is_ident_char(c) == 0 {
        endp = j
        break
      }

      if j == n-1 {
        endp = n
        break
      }

      off = off + 1
    }

    if endp == i { return null }
    return s.substring(i, endp)
  }

  // Helper: check if character is valid identifier character
  _is_ident_char(c) {
    if c == "_" { return 1 }
    if c >= "A" && c <= "Z" { return 1 }
    if c >= "a" && c <= "z" { return 1 }
    if c >= "0" && c <= "9" { return 1 }
    return 0
  }

  // Helper: split string into lines
  _split_lines(s) {
    local arr = new ArrayBox()
    if s == null { return arr }

    local n = s.length()
    local last = 0
    local i = 0

    loop (i < n) {
      local ch = s.substring(i, i+1)
      if ch == "\n" {
        arr.push(s.substring(last, i))
        last = i+1
      }
      i = i + 1
    }

    if last <= n {
      arr.push(s.substring(last))
    }

    return arr
  }

  // Helper: left trim
  _ltrim(s) {
    return me._ltrim_chars(s, " \t")
  }

  _ltrim_chars(s, cs) {
    local n = s.length()
    local head = 0
    local idx = 0

    while idx < n {
      local ch = s.substring(idx, idx+1)
      if ch != " " && ch != "\t" {
        head = idx
        break
      }
      if idx == n-1 {
        head = n
      }
      idx = idx + 1
    }

    return s.substring(head)
  }

  // Helper: right strip
  _rstrip(s) {
    local n = s.length()
    local last = n
    local r = 0

    while r < n {
      local i4 = n-1-r
      local c = s.substring(i4, i4+1)
      if c != " " && c != "\t" {
        last = i4+1
        break
      }
      if r == n-1 {
        last = 0
      }
      r = r + 1
    }

    return s.substring(0, last)
  }

  // Helper: integer to string
  _itoa(n) {
    local v = 0 + n
    if v == 0 { return "0" }

    local out = ""
    local digits = "0123456789"
    local tmp = ""

    while v > 0 {
      local d = v % 10
      tmp = digits.substring(d, d+1) + tmp
      v = v / 10
    }

    out = tmp
    return out
  }
}

static box RuleDeadCodeMain {
  method main(args) {
    return 0
  }
}