# Code Review - No Blocking Issues Found

## Summary
The implementation successfully addresses the critical issue with function call compilation. The addition of the `first_arg_reg` field to the `Call` instruction enables the VM to locate function arguments at runtime. All changes are well-tested and maintain backward compatibility.

## Acceptance Criteria Status
✅ **All acceptance criteria met:**
1. ✅ FunctionDef statements compile to DefineFunction instructions with correct metadata
2. ✅ Call expressions compile to Call instruction with argument setup in registers
3. ✅ Return statements compile to Return instruction (with or without value)
4. ✅ Compiler tracks function definitions separately from main code
5. ✅ Compiler allocates registers for arguments and return values
6. ✅ All existing compiler tests continue to pass (regression check) - 301 tests pass
7. ✅ At least 10 new compiler tests for function compilation - 14 function-related tests present

## Function Compilation Tests (14 total)
1. test_compile_function_def_no_params
2. test_compile_function_def_with_params
3. test_compile_function_call_no_args
4. test_compile_function_call_with_args
5. test_compile_return_with_value
6. test_compile_return_without_value
7. test_compile_function_scope_isolation
8. test_compile_multiple_functions
9. test_compile_nested_call
10. test_compile_function_with_complex_body
11. test_compile_function_call_with_expression_args
12. test_compile_function_register_allocation
13. test_compile_call_tracks_argument_registers ⭐ NEW
14. test_compile_call_no_args_first_arg_reg ⭐ NEW
15. test_compile_nested_calls_register_tracking ⭐ NEW

## No Blocking Issues
No security vulnerabilities, crashes, data loss issues, or fundamentally incorrect logic found.
