Input:
```rust
//- minicore: default
enum Variant<T> {
    Defined(T),
    Undefi$0ned,
}
```
Old:
```rust
enum Variant<T> {
    Defined(T),
    Undefined,
}

impl Default for Variant {
    fn default() -> Self {
        Self::Undefined
    }
}
```
This PR fixed:
```rust
enum Variant<T> {
    Defined(T),
    Undefined,
}

impl<T> Default for Variant<T> {
    fn default() -> Self {
        Self::Undefined
    }
}
```