hakorune/docs/private/roadmap/phases/phase-19-enum-match/day1-completion-report.md

Phase 19 Day 1 Completion Report - @enum Parser Extension

Date: 2025-10-08 Status: ✅ COMPLETED Duration: 1 day (estimated 1-2 days) Progress: Day 1/14 (7%)

---

🎯 Goal

Implement parser support for @enum syntax in Hakorune compiler.

Success Criteria:

• ✅ Parse @enum declarations
• ✅ Create appropriate AST nodes
• ✅ Integrate with existing parser infrastructure
• ✅ Pass compilation tests

---

✅ Deliverables

1. TokenType Extension

File: src/tokenizer/kinds.rs

Change: Added AT token type for @ character recognition.

pub enum TokenType {
    // ... existing tokens
    AT,  // NEW: @ for macro syntax
}

2. Tokenizer Extension

File: src/tokenizer/engine.rs

Change: Added @ character recognition in tokenizer.

'@' => {
    self.advance();
    Token::new(TokenType::AT, "@".to_string(), start_pos)
}

3. AST Extension

File: src/ast.rs

Changes:

• Added EnumVariant struct
• Added ASTNode::EnumDeclaration variant

pub struct EnumVariant {
    pub name: String,
    pub fields: Vec<String>,
}

pub enum ASTNode {
    // ... existing variants
    EnumDeclaration {
        name: String,
        variants: Vec<EnumVariant>,
    },
}

4. AST Utility Functions

File: src/ast/utils.rs

Changes: Added pattern matching for EnumDeclaration in 4 locations:

• clone_node()
• format_node()
• find_functions()
• collect_box_names()

ASTNode::EnumDeclaration { name, variants } => {
    // Implementation for each utility function
}

5. Enum Parser Implementation

File: src/parser/declarations/enum_parser.rs (NEW)

Lines: 150 Quality: Clean modular design

Key Functions:

• parse_enum_declaration() - Main entry point
• parse_enum_variant() - Parse individual variants
• Error handling with descriptive messages

Syntax Supported:

@enum Result {
    Ok(value)
    Err(error)
}

@enum Option {
    Some(value)
    None
}

6. Parser Integration

File: src/parser/declarations/mod.rs

Change: Exported enum_parser module.

pub mod enum_parser;

File: src/parser/statements/declarations.rs

Change: Added @ token dispatch to enum_parser.

if self.peek().token_type == TokenType::AT {
    return enum_parser::parse_enum_declaration(self);
}

File: src/parser/statements/mod.rs

Change: Added TokenType::AT recognition.

TokenType::AT => {
    return parse_declaration_statement(parser);
}

---

📊 Statistics

Code Metrics

• New Files: 1 (enum_parser.rs)
• Modified Files: 6
• Lines Added: ~150 (mostly enum_parser.rs)
• Lines Modified: ~20 (AST utilities + integration points)

Files Changed Summary

File	Type	Lines Changed	Description
src/tokenizer/kinds.rs	Modified	+1	Added AT token
src/tokenizer/engine.rs	Modified	+4	@ character recognition
src/ast.rs	Modified	+8	EnumVariant + ASTNode variant
src/ast/utils.rs	Modified	+12	Pattern matching in 4 functions
src/parser/declarations/enum_parser.rs	NEW	+150	Complete parser implementation
src/parser/declarations/mod.rs	Modified	+1	Module export
src/parser/statements/declarations.rs	Modified	+3	@ dispatch
src/parser/statements/mod.rs	Modified	+3	AT token recognition

Total: ~182 lines added/modified

---

🧪 Testing

Build Tests

cargo check
# Result: ✅ PASS

cargo build --release
# Result: ✅ PASS

Runtime Tests

Test Code:

@enum Result {
    Ok(value)
    Err(error)
}

@enum Option {
    Some(value)
    None
}

Result: ✅ PASS - Both enums parsed correctly

Verification:

• AST nodes created successfully
• Variants captured correctly
• Fields recognized properly
• No parser errors

---

💡 Implementation Highlights

Clean Architecture

1. Modular Design: Separate enum_parser.rs module
2. Clear Separation: Tokenizer → AST → Parser integration
3. Minimal Changes: Only necessary modifications to existing code
4. Type Safety: Strong typing throughout

Error Handling

Comprehensive error messages for:

• Missing enum name
• Missing opening brace
• Invalid variant syntax
• Missing variant name
• Missing closing brace

Extensibility

Design allows for future extensions:

• Generic parameters (future)
• Variant attributes (future)
• Complex field types (future)

---

🎓 Lessons Learned

What Went Well

1. Clean Separation: Modular design made implementation straightforward
2. Existing Patterns: Phase 16 @derive provided excellent reference
3. Strong Types: Rust's type system caught errors early
4. Test-Driven: Runtime tests validated implementation immediately

Challenges Encountered

1. AST Utilities: Required updates in 4 locations (clone, format, find, collect)

   • Solution: Systematic review of all utility functions

2. Parser Integration: Multiple integration points

   • Solution: Clear dispatch logic at each level

3. Token Recognition: @ character needed tokenizer support

   • Solution: Simple addition to tokenizer engine

Best Practices Applied

1. Incremental Testing: Tested after each major change
2. Code Review: Reviewed existing @derive implementation first
3. Documentation: Clear comments in code
4. Consistency: Followed existing code patterns

---

🔄 Next Steps (Day 2)

Macro Expansion Implementation

File: src/macro/enum_expander.rs (NEW)

Tasks:

1. Create enum_expander.rs in src/macro/
2. Implement enum_to_box_ast() transformation
3. Generate box with _tag field
4. Generate static box with constructors
5. Generate helper methods (is_*, as_*)
6. Integrate with MacroEngine::expand_node()
7. Write unit tests (10 patterns)
8. Write integration tests (3 .hako files)

Estimated Time: 6-8 hours

Desugaring Example:

// Input
@enum Result {
    Ok(value)
    Err(error)
}

// Output
box ResultBox {
    _tag: StringBox
    _value: Box
    _error: Box
}

static box Result {
    Ok(v) {
        local r = new ResultBox()
        r._tag = "Ok"
        r._value = v
        return r
    }

    Err(e) {
        local r = new ResultBox()
        r._tag = "Err"
        r._error = e
        return r
    }

    is_ok(r) { return r._tag == "Ok" }
    is_err(r) { return r._tag == "Err" }

    unwrap_ok(r) {
        if r._tag != "Ok" {
            panic("unwrap_ok called on Err")
        }
        return r._value
    }

    unwrap_err(r) {
        if r._tag != "Err" {
            panic("unwrap_err called on Ok")
        }
        return r._error
    }
}

---

📚 References

Implementation Files

• src/parser/declarations/enum_parser.rs - Main implementation
• src/ast.rs - AST node definitions
• src/tokenizer/kinds.rs - Token types

Related Work

• Phase 16: @derive macro implementation
• Phase 20: VariantBox Core design (future reference)

Documentation

• Phase 19 README
• Phase 19 Strategy Decision
• 00_MASTER_ROADMAP

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📝 Summary

Day 1 successfully completed all objectives:

✅ Parser Extension: Complete @enum syntax support ✅ AST Integration: Clean AST node design ✅ Tests Passing: All build and runtime tests pass ✅ Quality: Clean, modular, extensible code

Progress: 7% of Phase 19 complete (Day 1/14) Timeline: On track for 2-3 week completion Next: Day 2 - Macro expansion implementation

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Report Created: 2025-10-08 Author: Phase 19 Implementation Team Status: Day 1 ✅ COMPLETED