# Mojo Type Safety

> Validate type safety in Mojo code including parametric types and trait constraints. Use during code review or when type errors occur.

- Skill: `majiayu000/mojo-type-safety` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds add majiayu000/mojo-type-safety`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/mojo-type-safety/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/majiayu000/mojo-type-safety

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# Type Safety Validation Skill

Ensure Mojo code follows type safety principles.

## When to Use

- Type errors during compilation
- Code review for type safety
- Designing generic functions
- Working with trait constraints

## Quick Reference

```mojo
# Generic function with type parameter
fn add[dtype: DType](a: Scalar[dtype], b: Scalar[dtype]) -> Scalar[dtype]:
    return a + b

# Trait constraint
fn process[T: Copyable](data: T):
    let copy = data  # T is Copyable

# Compile-time check
@parameter
fn validate[size: Int]():
    constrained[size > 0, "Size must be positive"]()
```

## Workflow

1. **Add type annotations** - All parameters and returns
2. **Use type parameters** - For generic code
3. **Add trait constraints** - When required
4. **Run compiler** - Verify type checking passes
5. **Test generic code** - With multiple types

## Mojo-Specific Notes

- Prefer `fn` over `def` for type safety
- Generic type parameters use `[T]` syntax
- Traits constrain what operations are allowed
- Compile-time checks prevent runtime errors

## Error Handling

| Error | Cause | Solution |
|-------|-------|----------|
| `Missing type annotation` | Untyped parameter | Add `: Type` to parameter |
| `Type mismatch` | Incompatible types | Add explicit conversion |
| `Unsupported operation` | Trait not constrained | Add trait constraint |
| `Constraint failed` | Compile-time check failed | Verify constraint conditions |

## References

- `.claude/shared/mojo-guidelines.md` - Current syntax and patterns
- `.claude/shared/mojo-anti-patterns.md` - Common constructor mistakes