Background

The into conversion is quite powerful, and the pros and cons of it are quite clearly outlined in the docs.

One of the main cons is that it can result is fairly expensive conversions to take place implicitly.

The AsRef trait is specifically designed to perform cheap conversions.

One very common example I see is:

fn inspect_file(file: impl AsRef<Path>) { ... }

// which can be used

inspect_file("hello.rs")

The &str is cheaply converted into a &Path and handled internally.

Proposal

I think it would be good if Bon could allow marking certain types to support AsRef, in much the same way that into is implemented:

#[derive(Builder)]
struct Example {
    #[builder(into)] 
    name: String,

	#[builder(as_ref)]
    location: &Path,
}

The name would be as_ref as the snake_case equivalent of the trait AsRef.

Related Work

• Obviously, the implementation of into is related
• Also related: AsRef trait parameters #258

A note for the community from the maintainers

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