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//! Example to demonstrate how to use the `keep_default_for` attribute.
//!
//! The generated `impl` blocks generate an item for each trait item by
//! default. This means that default methods in traits are also implemented via
//! the proxy type. Sometimes, this is not what you want. One special case is
//! when the default method has where bounds that don't apply to the proxy
//! type.
use auto_impl::auto_impl;
#[auto_impl(&, Box)]
trait Foo {
fn required(&self) -> String;
// The generated impl for `&T` will not override this method.
#[auto_impl(keep_default_for(&))]
fn provided(&self) {
println!("Hello {}", self.required());
}
}
impl Foo for String {
fn required(&self) -> String {
self.clone()
}
fn provided(&self) {
println!("привет {}", self);
}
}
fn test_foo(x: impl Foo) {
x.provided();
}
fn main() {
let s = String::from("Peter");
// Output: "привет Peter", because `String` has overwritten the default
// method.
test_foo(s.clone());
// Output: "Hello Peter", because the method is not overwritten for the
// `&T` impl block.
test_foo(&s);
// Output: "привет Peter", because the `Box<T>` impl overwrites the method
// by default, if you don't specify `keep_default_for`.
test_foo(Box::new(s));
}
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