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hakorune/docs/examples/visibility_error.nyash
Moe Charm 55777a0735 feat: Implement field visibility (public/private) system
## Major Features Added

### Field Visibility System
- Added `private { ... }` and `public { ... }` blocks in box declarations
- Default visibility is now handled explicitly (fields must be in either block)
- Visibility checks enforced at both interpreter and VM levels

### Parser Enhancements
- Extended AST with public_fields and private_fields vectors
- Added parsing for visibility blocks in box definitions
- Maintained backward compatibility with existing `init { ... }` syntax

### Interpreter Implementation
- Added visibility checks in field access (get_field/set_field)
- External access to private fields now throws appropriate errors
- Internal access (within methods) always allowed

### VM Implementation
- Extended VM with object_class tracking for visibility checks
- RefGet/RefSet instructions now enforce field visibility
- Fixed nested box declaration collection (boxes defined inside methods)

### Test Examples Added
- docs/examples/visibility_ok.nyash - demonstrates correct usage
- docs/examples/visibility_error.nyash - tests private field access errors

## Technical Details

### Error Messages
- Interpreter: "Field 'X' is private in Y"
- VM: Same error message for consistency

### Current Limitations
- All RefGet/RefSet treated as external access in VM (internal flag future work)
- Legacy `init { ... }` fields treated as having unspecified visibility

## Test Results
 Interpreter: Both test cases pass correctly
 VM: Both test cases pass correctly after nested declaration fix

This implements the foundation for proper encapsulation in Nyash,
following the "explicit is better than implicit" philosophy.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
2025-08-21 03:08:13 +09:00

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static box Main {
init { console }
main() {
me.console = new ConsoleBox()
box User {
private { age, passwordHash }
public { name }
init { name, age }
birth(n, a) {
me.name = n
me.age = a
}
}
local u = new User("Alice", 20)
me.console.log("name(public)=" + u.name) # OK: public
# 以下は外部からprivateフィールドへのアクセス → エラーになる想定
u.age = 30 # 外部からの代入NG
me.console.log(u.age) # 外部からの参照NG
}
}