# REFCOUNT_SPEC.md — Executive Summary
**Full Spec:** `crates/tldr-core/src/analysis/REFCOUNT_SPEC.md` (1086 lines)
## What This Spec Defines
A complete behavioral specification for replacing the current call-graph-based dead code detector with a **reference-counting algorithm** that is:
- **71% more accurate** (eliminates false positives from callbacks, dict registration, dynamic dispatch)
- **40-50% faster** (single parse pass instead of two)
- **Backward compatible** (same API, same output format)
## The 12 Core Contracts
| **C1** | ref_count == 1 → DEAD (unless excluded) | New algorithm core |
| **C2** | ref_count > 1 → ALIVE (rescued by references) | New algorithm core |
| **C3** | Names < 3 chars → skip refcount (collision risk) | New safeguard |
| **C4** | Entry points (main, test_*, handle*) → EXCLUDED | Reuse `is_entry_point_name()` @ dead.rs:129 |
| **C5** | Dunder methods (`__xxx__`) → EXCLUDED | Reuse check @ dead.rs:73-78 |
| **C6** | Trait/interface methods → EXCLUDED | Reuse `is_trait_or_interface()` @ dead.rs:409 |
| **C7** | Test functions → EXCLUDED | Reuse test detection @ dead.rs:274-308 |
| **C8** | Decorated functions → EXCLUDED | Reuse decorator check @ dead.rs:90-93 |
| **C9** | Public uncalled → possibly_dead; Private uncalled → dead_functions | Reuse visibility @ dead.rs:314-406 |
| **C10** | Output format = types::DeadCodeReport (backward compat) | Reuse existing structure |
| **C11** | Parse each file ONCE (AST + identifiers combined) | New optimization |
| **C12** | Per-language tree-sitter queries (18 languages) | Oracle research Q2 |
## What to Reuse vs Replace
### REUSE (battle-tested logic)
- `is_entry_point_name()` — 50+ entry point patterns, 15+ tests
- `collect_all_functions()` — Metadata enrichment (decorators, visibility, traits)
- `is_test_file_path()` / `is_test_function_name()` / `has_test_decorator()` — Test detection
- `infer_visibility_from_name()` — Per-language visibility heuristics (16 languages)
- `is_trait_or_interface()` — Trait/interface detection
- `types::DeadCodeReport` — Output structure (backward compat)
- `FunctionRef` — Identity and metadata struct
### REPLACE (the core algorithm)
- Main loop in `dead_code_analysis()` (lines 39-106)
- Set-difference logic (`called_functions.contains()`)
- Unused `callers` HashSet (lines 49-55) — currently dead code
## Implementation Strategy
### Step 1: TDD — Write Failing Tests
Create `dead_refcount_tests.rs` with tests for all 12 contracts.
### Step 2: Combined Parse Pass
```rust
for each file:
tree = parse_with_tree_sitter(file, language)
definitions = extract_function_definitions(tree) // Existing logic
identifiers = extract_all_identifiers(tree) // NEW
ref_count[identifier.name] += 1 // NEW
```
### Step 3: Apply Exclusions + Classify
```rust
for func_def in definitions:
if ref_count[func_def.name] > 1 { continue; } // ALIVE (C2)
if func_def.name.len() < 3 { low_confidence; } // Short name (C3)
if is_entry_point(name) { continue; } // C4
if is_dunder(name) { continue; } // C5
if func_def.is_trait_method { continue; } // C6
if func_def.is_test { continue; } // C7
if func_def.has_decorator { continue; } // C8
// Classify by visibility (C9)
if func_def.is_public { possibly_dead } else { dead_functions }
```
### Step 4: Return DeadCodeReport (C10)
Same structure as existing — CLI and quality wrappers work unchanged.
## Per-Language Tree-sitter Queries (C12)
Complete reference table for 18 languages:
| Python | `function_definition` | `identifier` | `identifier` |
| Go | `function_declaration`, `method_declaration` | `identifier`, `field_identifier` | `identifier`, `field_identifier` |
| Rust | `function_item` | `identifier` | `identifier` |
| TypeScript/JS | `function_declaration`, `method_definition` | `identifier`, `property_identifier` | `identifier`, `property_identifier` |
| Java | `method_declaration` | `identifier` | `identifier` |
| C/C++ | `function_definition` (nested declarators) | `identifier` | `identifier` |
| Ruby | `method`, `singleton_method` | `identifier` | `identifier` |
| PHP | `function_definition`, `method_declaration` | `name` | `name` |
| Kotlin | `function_declaration` | `simple_identifier` | `simple_identifier` |
| Swift | `function_declaration` | `simple_identifier` | `simple_identifier` |
| C# | `method_declaration` | `identifier` | `identifier` |
| Scala | `function_definition` | `identifier` | `identifier` |
| Elixir | `call` (with def/defp target) | `identifier` | `identifier` |
| Lua/Luau | `function_declaration` | `identifier` / `dot_index_expression` | `identifier` |
| OCaml | `let_binding` | `value_name` | `value_name` |
Full query patterns provided in spec Section C12.
## Language-Specific Gotchas
| C/C++ | Nested declarators | Walk chain programmatically |
| Go | Methods use `field_identifier` | Query both identifier types |
| Elixir | `def` is a macro call | Match `call` nodes with def target |
| Lua | Compound names (`tbl.x.y`) | Extract last segment |
| OCaml | Functions are `let` bindings | Check if body is `fun_expression` |
## Testing Requirements
1. **Unit tests:** All 12 contracts (C1-C12) must have failing tests first
2. **Integration tests:** Compare old vs new algorithm on labeled corpus
3. **Performance test:** New algorithm ≥ 40% faster on 10k+ files
4. **Backward compat:** All existing tests in `dead.rs` must pass unchanged
5. **Per-language tests:** 18 languages × (definition extraction + identifier extraction)
## Success Criteria
1. All C1-C12 tests pass
2. All existing tests pass (backward compat)
3. ≥ 40% performance improvement
4. ≤ 30% false positive rate (down from ~71%)
5. CLI/quality integration works unchanged
6. Documentation updated
## Key Files Referenced
- **Existing implementation:** `crates/tldr-core/src/analysis/dead.rs` (lines 33-126 is core algorithm)
- **Type definitions:** `crates/tldr-core/src/types.rs` (FunctionRef:441, DeadCodeReport:797)
- **CLI entry point:** `crates/tldr-cli/src/commands/dead.rs`
- **Quality wrapper:** `crates/tldr-core/src/quality/dead_code.rs`
- **Oracle research:** `/Users/cosimo/.opc-dev/.claude/cache/agents/oracle/output-2026-02-12-refcount-dead-code.md`
- **Architecture map:** `/tmp/dead-command-map.md`
## Industry Validation
This algorithm is validated by:
- **Vulture (Python):** Most popular Python dead code tool uses AST name tracking (≈ our refcount approach)
- **Meta SCARF:** Uses textual reference search (BigGrep) as safety net for static analysis
- **unused tool:** Language-agnostic proof of concept using ctags + grep
- **Prototype results:** 71% FP reduction over call-graph analysis
## Next Steps for Implementation
1. **Hand off to kraken:** Implement failing tests for contracts C1-C12
2. **Architect review:** Validate algorithm design and performance assumptions
3. **Implementation:** Replace `dead_code_analysis()` body with new algorithm
4. **Validation:** A/B test old vs new on real codebases
5. **Cutover:** Deploy new algorithm, keep old as `_legacy()` for 2 weeks
6. **Deprecation:** Remove old algorithm after validation period
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**Total Spec Size:** 1086 lines, 12 behavioral contracts, 18 language mappings, complete test strategy