Add RedundantMemberwiseInit rule

[miguel-jimenez-0529]

Summary

This PR adds rule RedundantMemberwiseInit to automatically remove redundant memberwise initializers from structs when they only assign parameters to properties with matching names.

With --redundantmemberwise:

- struct Planet {
-   let name: String
-   let mass: Double
-   
-   init(name: String, mass: Double) {
-     self.name = name
-     self.mass = mass
-   }
- }

+ struct Planet {
+   let name: String
+   let mass: Double
+ }

Reasoning

Removing redundant memberwise initializers reduces boilerplate code and improves readability. The compiler can synthesize equivalent memberwise initializers automatically for structs, so explicit initializers that only perform simple property assignment are unnecessary. This rule helps maintain cleaner, more concise code while preserving the same functionality.

🤖 Generated with Claude Code

[calda]

Worth mentioning that this only applies to internal inits

Suggested change

* <a id='omit-redundant-memberwise-init'></a>(<a href='#omit-redundant-memberwise-init'>link</a>) **Omit redundant memberwise initializers.** The compiler can synthesize memberwise initializers for structs, so explicit initializers that only assign parameters to properties with the same names should be omitted. [](https://github.com/nicklockwood/SwiftFormat/blob/main/Rules.md#redundantMemberwiseInit)

* <a id='omit-redundant-memberwise-init'></a>(<a href='#omit-redundant-memberwise-init'>link</a>) **Omit redundant memberwise initializers.** The compiler synthesize internal memberwise initializers for structs, so explicit internal initializers that only assign parameters to properties with the same names should be omitted. [](https://github.com/nicklockwood/SwiftFormat/blob/main/Rules.md#redundantMemberwiseInit)

[miguel-jimenez-0529]

I think it can apply to private and fileprivate too. Let me update

[calda]

Maybe we should include an ALSO RIGHT: case with a public struct and a public init

[calda]

nice example 👌🏻

[calda]

Remember to update airbnb.swiftformat