Parser, Interpreter & Runtime Error Handling

📦 Release 0.6.0 — Parser, Interpreter & Runtime Error Handling

✨ Major Features

This major release marks a significant milestone for rslox — the language can now parse and evaluate expressions!

🎯 Core Language Features:

✅ Full Expression Parser:

• Binary operators: arithmetic (+, -, *, /), comparison (>, >=, <, <=), equality (==, !=)
• Unary operators: negation (-), logical NOT (!)
• Grouping expressions with parentheses
• Literal support: numbers, strings, booleans, nil
• Proper operator precedence and associativity

🚀 Interpreter with Evaluation:

• Complete expression evaluation system
• String concatenation support ("hello" + " world")
• Type checking for operations
• Runtime error detection:
  • Division by zero prevention
  • Type validation (e.g., can't negate a string)
  • Invalid operation detection

🛡️ Robust Error System:

• Separated error types for better debugging:
  • ScanErr — Lexical analysis errors
  • ParseErr — Syntax errors
  • RuntimeErr — Execution errors
  • SystemErr — File and IO errors
• Detailed error messages with line/position information
• Parse error recovery with synchronize() for REPL resilience

🧪 Quality Improvements:

✅ Unit Tests:

• Comprehensive interpreter tests
• Type error validation tests

🔄 Type System Refactor:

• Literal refactored from struct to enum with typed variants:
  • Literal::Number(f64)
  • Literal::String(String)
  • Literal::Boolean(bool)
  • Literal::Nil
• Better type safety and pattern matching

📚 Usage Examples:

Evaluate arithmetic expressions:

echo "1 + 2 * 3" | cargo run -- run
# Output: Number(7.0)

String concatenation:

echo '"Hello" + " " + "World"' | cargo run -- run
# Output: String("Hello World")

Runtime error handling:

echo "10 / 0" | cargo run -- run
# ERROR RUNTIME | Division by zero.

Debug mode with AST:

cargo run -- run -p playground/factorial.lox --show-ast