Symbol Table Management

Your Task

Implement a symbol table with proper scope management.

Requirements

1. Define data structures:

   • Symbol: Entry for one identifier
   • Scope: Collection of symbols with parent pointer
   • SymbolTable: Manages scope stack

2. Implement scope operations:

   • scope_enter(): Enter a new scope (function, block)
   • scope_exit(): Leave current scope
   • scope_current(): Get current scope level

3. Implement symbol operations:

   • symbol_define(name, type): Add symbol to current scope
   • symbol_lookup(name): Find symbol (current scope and parents)
   • symbol_lookup_local(name): Find symbol in current scope only
   • symbol_exists(name): Check if symbol is defined anywhere

4. Handle edge cases:

   • Redefinition in same scope → error
   • Shadowing in nested scope → allowed (warning optional)
   • Reference to undefined variable → error
   • Use before declaration (in same scope)

Success Criteria

• Track variables across nested scopes
• Detect redefinition errors
• Support variable shadowing
• Clean up symbols when scope exits