Type Checking

Your Task

Implement a type checker for your C subset.

Requirements

1. Define a type system:

   • Type enum: TYPE_INT, TYPE_CHAR, TYPE_VOID, TYPE_FLOAT, TYPE_ERROR
   • Type compatibility rules

2. Implement type checking functions:

   • check_expression(ASTNode*): Returns the type of an expression
   • check_statement(ASTNode*): Verifies statement type correctness
   • check_function(ASTNode*): Verifies function type correctness

3. Type rules to enforce:

   • Binary arithmetic: Both operands numeric, result is promoted type
   • Comparisons: Both operands numeric, result is int (boolean)
   • Assignment: Right side compatible with left side
   • Return: Expression type matches function return type
   • Function call: Argument types match parameter types

4. Error reporting:

   • Report type mismatches with location
   • Continue checking to find multiple errors
   • Return TYPE_ERROR for invalid expressions

Success Criteria

• Detect: int x = "hello"; (type mismatch)
• Detect: int foo(int x) { return "bad"; }
• Allow: int x = 5; float y = x; (implicit promotion)