Architectural Review - Next Steps

This document summarizes the architectural review deliverables and provides guidance on next steps.

📋 Deliverables

1. Comprehensive Review Report

File: docs/architectural-review-2025.md (1,344 lines)

A detailed architectural analysis covering: - Executive summary - 7 major architectural findings - 3 secondary findings
- Implementation roadmap - Priority matrix - Effort estimates - References and appendices

2. Issue Templates

Directory: docs/arch-review-issues/ (2,404 lines across 8 files)

Seven comprehensive issue templates ready to convert to GitHub issues:

Issue	Title	Severity	Effort	Labels
001	Parser Needs Error Recovery	CRITICAL	8 weeks	`arch-review`, `parser`, `ide-support`, `critical`
002	Implement Language Server Protocol	CRITICAL	20 weeks	`arch-review`, `ide-support`, `lsp`, `critical`
003	Implement Incremental Compilation	CRITICAL	20 weeks	`arch-review`, `performance`, `ide-support`, `critical`
004	Redesign Diagnostic System	HIGH	8 weeks	`arch-review`, `diagnostics`, `developer-experience`, `high`
005	Refactor to Composable Pipeline	HIGH	10 weeks	`arch-review`, `maintainability`, `performance`, `high`
006	Enhance Symbol Table Architecture	MEDIUM	8 weeks	`arch-review`, `symbol-table`, `performance`, `medium`
007	Restructure Testing Architecture	MEDIUM	10 weeks	`arch-review`, `testing`, `quality`, `medium`

🎯 Key Findings Summary

Critical Path Issues (P0)

These block IDE integration and prevent the compiler from scaling to production use:

Error Recovery (8 weeks): Parser throws on first error; must implement resilient parsing
LSP Implementation (20 weeks): No language server = no modern IDE support
Incremental Compilation (20 weeks): Full recompilation doesn't scale; blocks LSP performance

High Priority (P1)

Important for developer experience and maintainability:

Diagnostic System (8 weeks): Fragmented error reporting; poor error messages
Composable Pipeline (10 weeks): 18 hardcoded phases; difficult to test and optimize

Medium Priority (P2)

Performance and quality improvements:

Symbol Table (8 weeks): O(n) lookups; no indexing for IDE features
Testing Architecture (10 weeks): Slow tests; no unit/property testing

📅 Recommended Timeline

Q1 2026 (Jan-Mar)

Goal: Foundation for IDE integration

Weeks 1-8: Error Recovery + Diagnostic System
Weeks 1-10: Testing Architecture (ongoing)

Q2 2026 (Apr-Jun)

Goal: Ship working Language Server

Weeks 9-28: LSP Implementation (20 weeks)
Weeks 9-28: Incremental Compilation (20 weeks, parallel)
Weeks 9-18: Composable Pipeline (10 weeks)

Q3 2026 (Jul-Sep)

Goal: Performance and quality

Weeks 19-26: Symbol Table Enhancement
Weeks 1-26: Continue Testing Architecture

Total Effort: ~84 weeks (21 months) of work With 2-3 developers: ~6-9 months calendar time

✅ Next Steps

Immediate Actions

Review the findings with the team
Read docs/architectural-review-2025.md
Discuss priorities and timeline
Get team buy-in
Create GitHub issues from templates
Use the script in docs/arch-review-issues/README.md
Or create manually via GitHub web UI
Ensure all labels exist in the repository
Set up project board
Create GitHub project for "Architectural Improvements"
Add all issues to the board
Set up milestones for Q1, Q2, Q3 2026
Prioritize and schedule
Decide which issues to tackle first
Assign team members
Set realistic timelines

Short Term (This Month)

Start with Error Recovery (Issue #001)
This is the foundation for all other work
Relatively contained (8 weeks)
Enables LSP and better diagnostics
Set up Testing Infrastructure (Issue #007)
Run in parallel with Error Recovery
Improves confidence in changes
Enables phase isolation
Plan LSP Architecture
Review Issue #002 in detail
Evaluate OmniSharp LSP library
Design service interfaces

Medium Term (Next Quarter)

Ship Error Recovery
Complete implementation
Full test coverage
Update documentation
Redesign Diagnostic System
While Error Recovery is in progress
Creates foundation for great error messages
Begin LSP Implementation
Once Error Recovery is complete
Start with basic features (diagnostics, hover)

Long Term (6-9 Months)

Complete LSP with basic features
Implement Incremental Compilation
Refactor Pipeline Architecture
Ship production-ready compiler with IDE support

🚀 Success Criteria

By end of Q3 2026, the compiler should have:

✅ Resilient parser with error recovery
✅ Working Language Server with basic features
✅ Incremental compilation (10x+ speedup)
✅ High-quality error messages (like Rust)
✅ Composable pipeline architecture
✅ Fast symbol lookups (O(1))
✅ Comprehensive test coverage (>80%)

📚 Resources

Documentation

Full Review: docs/architectural-review-2025.md
Issue Templates: docs/arch-review-issues/
Issue Creation Guide: docs/arch-review-issues/README.md

References

LSP Specification: https://microsoft.github.io/language-server-protocol/
Rust Compiler Dev Guide: https://rustc-dev-guide.rust-lang.org/
ANTLR Error Recovery: https://www.antlr.org/papers/erro.pdf
Property-Based Testing: https://fscheck.github.io/FsCheck/

Example Implementations

Rust Analyzer (LSP): https://github.com/rust-lang/rust-analyzer
Roslyn (C# compiler): https://github.com/dotnet/roslyn
TypeScript (incremental): https://github.com/microsoft/TypeScript

💡 Final Thoughts

The Fifth language compiler has a solid foundation but requires significant architectural investment to compete with modern languages. The three critical issues (Error Recovery, LSP, Incremental Compilation) form a critical path that must be addressed for the language to succeed.

Good news: The issues are well-understood and have clear solutions based on proven compiler design patterns. With dedicated effort, Fifth can have best-in-class tooling within 6-9 months.

Recommendation: Start with Error Recovery (foundational) and Testing Architecture (enables confidence), then move to LSP (biggest impact on adoption).

Questions? Refer to the full architectural review document or individual issue templates for detailed information.