Macro setter

macro_rules! setter {
    ($name:ident, $type:ty) => { ... };
    ($name:ident, into $type:ty) => { ... };
}

A macro for generating builder-style setter methods.

This macro provides two variants:

1. Direct assignment: setter!(field_name, FieldType)
2. Automatic Into conversion: setter!(field_name, into TargetType)

Examples

struct Builder {
    name: Option<String>,
    count: Option<u32>,
}

impl Builder {
    setter!(name, into String);  // Accepts any type that implements Into<String>
    setter!(count, u32);         // Only accepts u32

    pub fn build(self) -> Self {
        self
    }
}

let builder = Builder {
    name: None,
    count: None,
}
.name("test")    // &str automatically converted to String
.count(42);      // Direct u32 assignment