---
title: Add TypeScript grammar for decy target
issue: VERIFICAR-041
status: Complete
created: 2025-11-30T00:00:00Z
updated: 2025-11-30T21:30:00Z
---

# Add TypeScript grammar for decy target Specification

**Ticket ID**: VERIFICAR-041
**Status**: Complete

## Summary

Implements TypeScript grammar support for verificar, enabling validation of TypeScript code
generated as a target language for the decy transpiler (C → TypeScript). Uses tree-sitter-typescript
for accurate AST-based validation when the `tree-sitter` feature is enabled.

## Requirements

### Functional Requirements
- [x] TypeScript grammar with syntax validation
- [x] Support for TypeScript-specific features (interfaces, type annotations, generics)
- [x] tree-sitter integration for accurate AST parsing
- [x] Fallback heuristic validation without tree-sitter
- [x] Integration with Language enum and grammar_for() factory

### Non-Functional Requirements
- [x] Performance: Sub-millisecond validation for typical code snippets
- [x] Test coverage: 100% (achieved)

## Architecture

### Design Overview

TypeScript grammar follows the existing pattern established by Python, C, and Bash grammars:
- `TypeScriptGrammar` struct implementing the `Grammar` trait
- Optional tree-sitter integration via feature flag
- Fallback to bracket-balancing heuristics without tree-sitter

### API Design

```rust
use verificar::grammar::{Grammar, TypeScriptGrammar};
use verificar::Language;

// Create TypeScript grammar
let grammar = TypeScriptGrammar::new();

// Validate TypeScript code
assert!(grammar.validate("let x: number = 42;"));
assert!(grammar.validate("interface Foo { bar: string; }"));

// Use via factory
let grammar = verificar::grammar::grammar_for(Language::TypeScript);
```

## Implementation Plan

### Phase 1: Foundation ✅
- [x] Add `TypeScript` variant to `Language` enum
- [x] Add tree-sitter-typescript dependency

### Phase 2: Core Implementation ✅
- [x] Create `TypeScriptGrammar` struct
- [x] Implement `Grammar` trait
- [x] Add tree-sitter parsing methods
- [x] Update `grammar_for()` factory

## Testing Strategy

### Unit Tests (13 tests, 100% coverage)
- [x] test_typescript_grammar_language
- [x] test_typescript_grammar_validate_basic
- [x] test_typescript_grammar_validate_function
- [x] test_typescript_grammar_validate_interface
- [x] test_typescript_grammar_validate_class
- [x] test_typescript_grammar_validate_type_annotations
- [x] test_typescript_grammar_validate_generics
- [x] test_typescript_grammar_validate_control_flow
- [x] test_typescript_grammar_validate_async
- [x] test_typescript_grammar_validate_unbalanced
- [x] test_typescript_grammar_max_depth
- [x] test_typescript_grammar_debug
- [x] test_typescript_grammar_default

### Tree-sitter Feature Tests
- [x] test_parse_simple
- [x] test_root_node
- [x] test_has_errors_valid
- [x] test_has_errors_invalid
- [x] test_ast_depth
- [x] test_node_count
- [x] test_typescript_specific_syntax

## Success Criteria

- ✅ All acceptance criteria met
- ✅ Test coverage: 100% (line, function, region)
- ✅ Zero clippy warnings
- ✅ Documentation complete
- ✅ Integrated with existing grammar infrastructure

## Implementation Details

### Files Modified
- `Cargo.toml` - Added tree-sitter-typescript dependency
- `src/lib.rs` - Added `TypeScript` to `Language` enum
- `src/grammar/mod.rs` - Added TypeScript module and grammar_for() case
- `src/generator/mod.rs` - Handle TypeScript in generate_exhaustive()

### Files Created
- `src/grammar/typescript.rs` - TypeScript grammar implementation (233 lines)

## References

- [tree-sitter-typescript](https://crates.io/crates/tree-sitter-typescript)
- Existing grammar implementations: python.rs, c.rs, bash.rs, ruchy.rs
