Constant Folding

Your Task

Implement constant folding as an AST optimization pass.

Requirements

1. Implement fold_expression() that:

   • Traverses the AST
   • Evaluates constant expressions
   • Replaces them with literal nodes

2. Handle these operations:

   • Arithmetic: +, -, *, /, %
   • Comparisons: <, >, <=, >=, ==, !=
   • Logical: &&, ||, !
   • Unary: -, !

3. Handle edge cases:

   • Division by zero: Keep original expression (runtime error)
   • Integer overflow: Wrap or report warning
   • Mixed types: Apply type promotion rules

4. Fold nested expressions:

   • (1 + 2) * (3 + 4) → 21

Success Criteria

• 2 + 3 → 5 (literal node)
• x + 0 → x (identity optimization)
• x * 1 → x (identity optimization)
• 0 * x → 0 (if no side effects)