What is the difference between clone() and copy?

Question

Accepted Answer

**clone()** — explicit deep copy. **Copy** — implicit bitwise copy.

**clone():**
- Explicitly called.
- Deep copy — duplicates heap data.
- Can be expensive.
- Works for any `Clone` type.
- Both variables independent after.

```rust
let s1 = String::from("hello");
let s2 = s1.clone();
println!("{} {}", s1, s2);  // Both valid

let v1 = vec![1, 2, 3];
let v2 = v1.clone();
```

**Copy trait:**
- Implicit — on assignment.
- Bitwise — no heap.
- Only for trivially copyable types.
- Must implement `Clone` too.
- Both valid after.

```rust
let x: i32 = 42;
let y = x;
println!("{} {}", x, y);  // 42 42

let pair = (1, 2.0);
let pair2 = pair;
```

**When to use:**
- Use `clone()` for explicit ownership.
- Small types copy automatically.
- Prefer borrowing.

**Common mistakes:**
- Cloning when borrowing works.
- Thinking `String` is `Copy`.
- Implementing `Copy` for heap types.

Rust: What is the difference between clone() and copy?