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# What `#[derive(IsVariant)]` generates
When an enum is decorated with `#[derive(IsVariant)]`, for each variant `foo` in
the enum, a public instance method `is_foo(&self) -> bool` is generated. If you
don't want the `is_foo` method generated for a variant you can put the
`#[is_variant(ignore)]` attribute on that variant.
## Example usage
```rust
# use derive_more::IsVariant;
#
#[derive(IsVariant)]
enum Maybe<T> {
Just(T),
Nothing
}
assert!(Maybe::<()>::Nothing.is_nothing());
assert!(!Maybe::<()>::Nothing.is_just());
```
### What is generated?
The derive in the above example generates code like this:
```rust
# enum Maybe<T> {
# Just(T),
# Nothing
# }
impl<T> Maybe<T>{
#[must_use]
pub const fn is_just(&self) -> bool {
matches!(self, Self::Just(..))
}
#[must_use]
pub const fn is_nothing(&self) -> bool {
matches!(self, Self::Nothing)
}
}
```
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