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npx skills add actionbook/rust-skills --skill m01-ownership
CRITICAL: Use for ownership/borrow/lifetime issues. Triggers: E0382, E0597, E0506, E0507, E0515, E0716, E0106, value moved, borrowed value does not live long enough, cannot move out of, use of moved value, ownership, borrow, lifetime, 'a, 'static, move, clone, Copy, 所有权, 借用, 生命周期
npx skills add actionbook/rust-skills --skill m01-ownership
Layer 1: Language Mechanics
Who should own this data, and for how long?
Before fixing ownership errors, understand the data's role:
| Error | Don't Just Say | Ask Instead |
|---|---|---|
| E0382 | "Clone it" | Who should own this data? |
| E0597 | "Extend lifetime" | Is the scope boundary correct? |
| E0506 | "End borrow first" | Should mutation happen elsewhere? |
| E0507 | "Clone before move" | Why are we moving from a reference? |
| E0515 | "Return owned" | Should caller own the data? |
| E0716 | "Bind to variable" | Why is this temporary? |
| E0106 | "Add 'a" | What is the actual lifetime relationship? |
Before fixing an ownership error, ask:
What is this data's domain role?
Is the ownership design intentional?
Fix symptom or redesign?
When errors persist, trace to design layer:
| Persistent Error | Trace To | Question |
|---|---|---|
| E0382 repeated | m02-resource | Should use Arc/Rc for sharing? |
| E0597 repeated | m09-domain | Is scope boundary at right place? |
| E0506/E0507 | m03-mutability | Should use interior mutability? |
From design decisions to implementation:
| Pattern | Ownership | Cost | Use When |
|---|---|---|---|
| Move | Transfer | Zero | Caller doesn't need data |
&T | Borrow | Zero | Read-only access |
&mut T | Exclusive borrow | Zero | Need to modify |
clone() | Duplicate | Alloc + copy | Actually need a copy |
Rc<T> | Shared (single) | Ref count | Single-thread sharing |
Arc<T> | Shared (multi) | Atomic ref count | Multi-thread sharing |
Cow<T> | Clone-on-write | Alloc if mutated | Might modify |
| Error | Cause | Quick Fix |
|---|---|---|
| E0382 | Value moved | Clone, reference, or redesign ownership |
| E0597 | Reference outlives owner | Extend owner scope or restructure |
| E0506 | Assign while borrowed | End borrow before mutation |
| E0507 | Move out of borrowed | Clone or use reference |
| E0515 | Return local reference | Return owned value |
| E0716 | Temporary dropped | Bind to variable |
| E0106 | Missing lifetime | Add 'a annotation |
| Anti-Pattern | Why Bad | Better |
|---|---|---|
.clone() everywhere | Hides design issues | Design ownership properly |
| Fight borrow checker | Increases complexity | Work with the compiler |
'static for everything | Restricts flexibility | Use appropriate lifetimes |
Leak with Box::leak | Memory leak | Proper lifetime design |
| When | See |
|---|---|
| Need smart pointers | m02-resource |
| Need interior mutability | m03-mutability |
| Data is domain entity | m09-domain |
| Learning ownership concepts | m14-mental-model |