Overview

deriving lens for custom data types.

see the guide

Example

```rust

[derive(Debug, Optic, Lens)]

struct Baz<'a, A, B, C>{ #[optic(ref)] a: &'a A, // can only take the immutable ref by optics::a #[optic(mut)] b: &'a mut B, // can take the mutable ref by optics::b #[optic] c: C // can mv it out by by optics::c }

[derive(Optic, Review, Prism, Debug)]

enum AnEnum { A(T, i32), #[optic] B(T), }

[derive(Optic, Lens, Debug)]

struct Foo { #[optic] a: i32, #[optic] b: i32, }

fn test() -> Option<()> { let x = Review::review(optics!(Some.B), Foo { a: 3, b: 2, }); assert_eq!(x.preview(optics!(Some.B.b))?, 2);

Some(())

} ```

Limitation

• can't derive Lens for enum.
• can't derive Prism and Review for the variant has more than one argument or has named field.